DEEPER BASS: D. B. KEELE/E-V's STEP-DOWN MODE [Archive]

RMC

01-22-2018, 08:28 PM

DEEPER BASS, PART 1, ELECTRO-VOICE

Here is how Electro-Voice describes, in simpler terms than D. B. Keele, the "Step-Down" operation (lower tuning than normal + EQ) to get lower bass from a smaller box:

"... the "step-down" mode, which approximates a B6 Thiele alignment. Step down is a good way to extend system low-frequency response by increasing amplifier power at certain frequencies instead of enclosure size.

In step down, the enclosure is tuned to a lower-than-normal frequency. This increases system output at the new tuning frequency and reduces output slightly in the region of original tuning. The smoothly falling response which results can be equalized to provide a new system 3-db-down point that is about 0.7 that of the original. To achieve a similar response extention without equalization would require an enclosure at least twice the size.

In the step-down mode, system input is increased at the lower end of the operating range, by a maximum of 6 db close to the new tuning frequency. Note that this boost does not affect system instantaneous peak output, which is related only to the speaker's linear displacement ability and effective diaphragm area."

The frequency where an increase is applied (EQ) is called a "peak-boost frequency". According to E-V, other frequencies sufficiently close, within + or - 5%, will provide no significant performance compromise.

With regards to Subpassband speaker protection (the other side of the coin) here is what E-V says:

"Below the enclosure tuning frequency, cone excursion increases rapidly. Since acoustic output is also falling rapidly, there is no utility in driving the system with signals much below the tuning frequency. (...). ... high output systems, especially subwoofer systems, should be protected by a high-pass filter with a 3-db-down corner frequency of about 0.8 the enclosure tuning frequency... Below the corner frequency, a rolloff of 12 db per octave is usually sufficient."

So, an amplitude boost followed by a bandwidth cut, that E-V calls "boost-and-cut equalization". "The equalization has no effect on the large-signal output but does have the effect of separating the small- and large-signal curves except at the very top of the frequency range shown."

Quoted from: Electro-Voice, Pro Sound Facts, #7, oct. 1984, pages 3 and 5

See Figure 3 in the XEQ-2 crossover/equalizer data sheet to look at examples of increases applied at various frequencies (+ 6 db boost with a filter Q of 2 and high-pass filter of 12 db/oct.).

E-V did not mention, in this context, the LF room gain possibility based on speaker placement.

More interesting stuff to come from E-V and D. B. Keele in subsequent posts.

Richard

RMC

01-22-2018, 08:31 PM

DEEPER BASS, PART 2, D.B. KEELE

As indicated in an earlier post, here is the second part of the "Step-Down Mode" information, this time from D. B. Keele(1).

Keele started with different driver types, modeled them in conventional LF alignments (e.g. B4, Qb3, C4, closed box) and also simulated new pseudo-sixth-order alignments to compare results with those. He adds that all the new alignments have coincident F3, Fb and maximum boost frequencies (p. 354).

Though Keele talks about a "modest amount of lift" (+ 6 db at the peak boost frequency in the bass range, 1.07 times F3), doing this requires four times the amount of power. What would otherwise be driven with 25 watts now requires 100, and what would otherwise have taken 100 now requires 400 Watts. Not really modest in my view, however today the cost of Watts can be pretty cheap.

Keele also says "It must be stressed that these alignments represent only discrete selections from a continuum of possible alignments." (p. 355) So there's a lot more than meets the eye (e.g. E-V's).

Keele says its not driver Fs that's important but Fs divided by Qt which indicates how low a driver will go. Adding for a desired F3 in the 25-50 hz range, Fs/Qt can be from about 80 to 160 hz. Drivers with that ratio would be likely candidates for B6 alignments. BTW for example the Fs/Qt ratio for JBL's 1400 ND stands at 106, therefore within that range.

Talking about a system aligned for a B4 response (F3= Fb=40hz) converted to a pseudo-B6 alignment (F3=Fb=28hz, boost @ 30hz ) Keele mentions "The net effect on the system response is one-half octave extention of low-frequency response with only about 3 db less maximum acoustic power output capability in the passband." (p.356) Three db is a notable quantity and represents half the power. The lower tuning and EQ boost will return the response back to a roughly flat condition according to Keele. That conversion "... somewhat reduces the maximum acoustic output capabilities of the system in the 35-70 hz range, but greatly increases the maximum output below 35 hz" (p. 357)

In his concluding summary, Keele mentions using these "... alignments offers real advantages in providing maximum useful low-frequency acoustic output while minimizing driver diaphragm excursion both in and out of the systems operating frequency range." (p. 357).

In another quasi-sixth-order (QB6) box he simulated (Fb=Faux=F3= 26 hz), the 6 db peak boost from auxiliary circuit happens at 1.07 times Fb = 28 hz (p. 358). (Faux being the frequency of the auxiliary peak boost filter, as I understand).

Note that in the simulations Keele did, when the new Fb was at 26 hz the 6 db boost was applied at 28 hz, for Fb 28 hz it was applied at 30 hz and for Fb 43 hz it was applied at 46 hz. Not exactly at Fb...

Also interesting to note that for a 4 cu. ft. box Keele used about 20% overvolume to compensate for box losses, while using 30% overvolume to offset box losses for a 7.5 cu. ft. box. More overvolume for larger boxes and less for smaller ones appears to agree with Leach (2) who suggests to use lower QL number for larger boxes and higher QL number for smaller boxes. That means larger boxes are more lossy than small ones. In the computer design process, entry of a lower QL will lead to a larger volume (Vb), and entry of a higher QL number leads to a smaller box. Unfortunately, Leach did not mention which higher or lower QL to use, but he did mention the initial design process with QL 7 is correct, and QL 7 good for 2 to 3 cu. ft. boxes. I would probably use QL 5 for larger boxes and QL 10 for smaller ones.

I have some issues with Keele's article and also with some E-V Step-Down Mode items which I'll cover in a future post.

Richard

(1) A New Set of Sixth-Order Vented-Box Loudspeaker System Alignments, JAES, 06-1975, P. 354. This can be found on his Website, dbkeele.com, AES papers, item # 8.

(2) W. Marshall Leach Jr., Vented-Box Loudspeaker Design with a Given Driver, 2001, P. 1, available on Net.

RMC

01-22-2018, 08:33 PM

DEEPER BASS, PART 3, EQ

STEPPING-DOWN WITH A REGULAR EQUALIZER? (For Didier and Rob in Europe, and other members)

For cost reasons a number of people will be tempted to use their present equalizer instead of making or purchasing a dedicated boost & cut filter. Hopefully, it will work correctly knowing what to watch for.

In simple terms, the filter Q number of the 6 db peak boost filter (Q 2) referred to in E-V's litterature for step-down EQ, refers to the shape of its response (symmetrical bell shape). The important parameter of that filter's response is the ratio of its height to its width (called "Q") which determines bandwidth. Low Q means wider shape and high Q means narrower.

The ideal situation is if you have access to Parametric EQ where you can define bandwidth, frequency and amplitude. Failing that, graphic EQ MAY still work if you have a slider at the right center frequency (or pretty close), among other conditions. 1/3 octave models offer much more center frequencies than 2/3 octave models, but instinctively the more sliders on an EQ the narrower the filters have to be (higher Q). That in order to minimize overlapping/interaction problems with other filters next to the one(s) used.

For graphic EQ, the next thing you need to know is the applicable filter Q number with regards to the sliders. Many EQ manuals don't elaborate much on this: "Constant Q filters, accuracy 3%" as do my 2/3 oct. Pro models. But I also have an older octave band Hi-Fi EQ and the manual says: "Filter Q 2.5 nominal, + or - 10% ." The manufacturer describes his filters as being medium Q. It has sliders at 30, 60, 120hz, etc. which don't offer a lot of practical center frequencies for Step-Down operation, however the 30 hz slider could be a good prospect for SOME typical Step-down applications.

A little higher than needed Q number indicating filter width being slightly narrower than perfect fit (Q 2). Such filter will have a little less "reach" on both sides of the underdamped filter's peak boost frequency. Assuming better filter tolerance than 10%, which does happen with audio gear specs being better than stated (E-V requires 5% tolerance here), that would still likely mean: a small dip in LF response above Faux (peak boost frequency of auxiliary filter), plus a little earlier drop in LF response below Faux, therefore a bit less deeper bass. Although not perfect, that case may still be acceptable for some. A slight negative ripple on both sides of that filter would imply a LF response less roughly flat as it could be after EQ is applied.

A boosting filter with a narrower impact on VLF isn't necessarily a bad idea since it reduces the risk of excessive cone travel if there's no VLF High-Pass Filter on the EQ, E-Xover or Amp. {This is where the issue of the step-down required high-pass filter of 12 db/oct. below Faux is relevant, more so if none is built-in the gear used}. On the negative side, since the boosting filter won't impact as low as ideal, one won't get the full step-down low-bass benefit (but then that should help a little on cone excursion in the absence of the high-pass filter).

In the event that a high-pass filter is present in the gear used, its corner frequency must be just below Faux action for best results, since above this it kind of defeats the purpose of boost equalization, and if its too low it doesn't help much cone travel/box unloading. Again, when a driver is working at or close to Fb the cone travel beware is less an issue, its more below box tuning region that caution must be used...

BTW just to make things clear, in the real thing (E-V's boost/cut EQ) the SAME filter does both tasks of VLF reduction/protection AND 6 db peak boost since it is an underdamped (peaky) 12 db/oct. high-pass filter. It "hits two birds with one stone" as they say. In the equalizer thing you need TWO filters to do the job correctly: one for 6 db peak boost (i.e. eq slider) and one for reduction/protection from VLF. Since one of my Pro EQ has a variable (20-200 hz) low-cut (high-pass) filter of 12 db/oct. I may try this EQ thing one day...

Another post will follow in the near future about some issues I have with Keele/E-V step-down process.

Richard

Robh3606

01-23-2018, 10:21 AM

Here is what a BX-63A hooked up to CLIO looks like. Attached are two plots that have the low frequency output measured at 63Hz, 90Hz and 125Hz and a second which has the high pass with the 125Hz curve. Seems relevant as it was EQ supplied for the B380 and 460. There is also an option the JBL 5235 active crossover around 30hz or so very similar.

Rob:)

RMC

01-23-2018, 09:51 PM

Hi Robh,

Quite Interesting input, and thanks for the attachements. I have not found a detailed data sheet for BX 63/A, other than JBL Pro Service Technical Manual which doesn't mention what I needed to know.

"Seems relevant as it was EQ supplied for the B380 and 460" You're absolutely right its relevant! JBL's BX63 was in fact used in the Kramer/Timbers article I referred to in post # 1 (introduction), where I mentioned " (e.g. Lorr Kramer and Greg Timbers did model a classic sixth-order alignment with the 2245H woofer ....)"

I should have expanded more on JBL's own "Step-Down" and the BX 63 in a JBL related Web site, MEA CULPA. My only excuse: I find JBL's "step-down" application somewhat limited VS Keele/E-V's pretty large application.

As for "There is also an option the JBL 5235 active crossover around 30hz or so very similar." you ARE right on target. BTW Recently I pulled-out my JBL file to review some older info to contribute to "Favorite JBL speakers" Thread (where I voted only for HLA Series! that should put some "ambience" in the 43 series club), and realized I had for a long time in my file (kept at arm's reach just in case it gets noisy) the 5235 data sheet 8/89 I had not seen for years (lucky me!).

In the product Features on front page, it mentions "Swithchable subsonic high-pass functions", not telling the whole story re capabilities. However, on the back side Specifications in the High pass filtering section, there you get it: 20hz, +6db, filter Q 2; 30hz, +6db, filter Q 2; 40hz, +6db, Filter Q 2. The other filtering options (other than crossover cards) are more for "subsonic" removal. All the filters for EQ boost & subsonic are given at 12db/oct. slope. So, JBL is in the game too.

I wrote "That info regarding a derivative of the B6 LF alignment may well be relevant even with some JBL drivers" That meant Keele's/E-V's stuff may also be used with some JBL drivers (ref. Keele's Fs/Qt), which opens more doors and applications in my view.

Since the BX 63 and/or 5235 are limited to certain frequencies (e.g. 20, 30, 40 hz) and Keele says "It must be stressed that these alignments represent only discrete selections from a continuum of possible alignments." then the possibilities become numerous...

Finally, In the E-V XEQ- 2/3 data sheets one can find the formulas to calculate their own custom filters. I'm not pretending that one manufacturer's stuff is better than the other, but simply that one gives more detailed info to the speaker builder on this subject and provides more flexibility. Best regards,

Richard

dn92

01-24-2018, 12:58 AM

In 5235
It is possible to change the filter tuning frequency but some résistors have to be changed on the main PCB.

Does someone know the volume and port tuning of a B380, just to understand how this fit to the natural response curve ?

Lee in Montreal

01-24-2018, 01:05 AM

Kef Kube - Q transformer
Small box. Deep bass. Beware of over excursion and clipping amp.

http://www.allegrosound.com/KEF_R107_fig-01.jpg

http://www.philipsradios.nl/forum/images/uploaded/201011012030294ccf1555e315b.jpg

https://lh6.googleusercontent.com/-ExSSj2zV2NU/T6C7XRL8X8I/AAAAAAAAJIQ/Dtcg7nKnACQ/s576/kef1-1.jpg

Ian Mackenzie

01-24-2018, 10:12 AM

Hi Richard and others

Attached is a spice simulation of a circuit l located over on diyaudio.com for the boost- cut equalisation
It was posted by an engineer. I have not evaluated this myself but l understand is what is referred to as an under - damped high pass filter.

The effect of varying the Q of the filter at the resonant frequency is the Peak or boost, below this frequency is the high pass filter. This is accomplished with a potentiometer

The frequency of the filter can be adjusted with another potentiometer

The practical application of this is straight forward for the diyaudio folks.

I understand that a short form kit was available from the engineer who submitted the above spice model

It was a while ago so l will see if this kit is still available?

This application would be an in out black box pre a power amplifier much like the EV box used for domestic models.

The Jbl BX 63 had as l recall the filter as described above in addition to a crossover function accompanied with a passive RC time constant to maintain purity of the audio signal for satellite loudspeaker.

The EV documents do refer to 4x the power and l note Dayton Audio through Parts Express have plate amps with dsp equalisation that can be programmed for boost- cut equalisation. The Dayton product kills two birds with one stone and may be an opportunity for anyone wants to try out the step down.

Below l found a collection of documents on the subject of Ev step down in production of PA loudspeakers

There are graphs that illustrate the impact of the step down.
I draw no conclusions from these links other than a Ev did apply the idea in commercial systems

In the last link there is a collection of vintage approaches to bass equalisation and if you scroll down the EV domestic step down product. Interesting

These are only links so open the doc and it’s quite easy to read.

http://pdf.textfiles.com/manuals/STARINMANUALS/Bosch%20-%20EV/TL3512.pdf

https://electrovoice.com/binary/TL440_Engineering_Data_Sheet.pdf

https://www.scribd.com/mobile/doc/14994220/EV-Pro-Sound-Facts-and-Speaker-Plans

http://www.roger-russell.com/equalizers/equalizers.htm

RMC

01-24-2018, 04:19 PM

Robh3606

01-24-2018, 06:44 PM

Does someone know the volume and port tuning of a B380, just to understand how this fit to the natural response curve ?

Hello

The box was 4.5 cubic feet and the tuning was 26Hz I have plotted both the response for both the equalized version and the box with no EQ at an input of 150 watts. You can clearly see the effect of the EQ in the displacement curves. They are great for music but looking at the displacement it's no wonder they can run into trouble used as subs in a modern HT system.

Rob :)

Ian Mackenzie

01-24-2018, 08:39 PM

Hi Rob,

Do you use your 2235's as B380's or if not would you consider it?

RMC

01-24-2018, 10:02 PM

Hi Robh,

Thanks for the simulation in post # 11. A few things aren't clear to me.

What are the boosting filter parameters you applied (frequency, amplitude, and Q or bandwidth) ?
Any LF subpassband filtering applied ?

On the bottom graph you have TWO response curves (orange and red). But on the top graph I see THREE cone excursion curves ! (two orange at Fb and one red). The orange curves are typical shape of cone travel in a vented box. However, the red excursion curve, looking like a pair of boobs, isn't typical for a vented box...

Finally, I notice on the red excursion curve that the right hand bump is at almost 8mm @35 hz, Xmax being 8.5 mm, and the left hand bump, around 20 hz, about 7+ mm, for the same input power but with even lower frequency! Effect of subpassband filtering ?

Richard

Robh3606

01-25-2018, 08:38 AM

Hi Rob,

Do you use your 2235's as B380's or if not would you consider it?

Hello Ian

Well actually I do use them as B380's. Remember my old LE-14 subs under my HT mains?? They have been replaced by a pair of B380's. I originally got a pair of 136Hs to run as subs in my HT but every once in a while I would slap a mass ring which is a bit alarming. So I set them up as stereo music subs and got a pair of 2266's and set them up as HT subs. Use the DSP in a crown amp to simulate a BX-63 so same idea in a smaller box higher x max and power handling.

http://www.audioheritage.org/vbulletin/showthread.php?33133-2266H-Any-users-out-there&highlight=bx63

Rob:)

Ian Mackenzie

01-25-2018, 11:26 AM

http://www.audioheritage.org/vbulletin/showthread.php?33133-2266H-Any-users-out-there&p=336627&viewfull=1#post336627

Hi Rob,

Excellent. Your real thorough.

The WT2 with BassBox Pro is a great combo.

That must have been after the last time I was at yours.

Great thread on how to do a diy sub right with some real practical experience.

Glad you bought up the mass ring slapping with the 2235s. I recall Mr Widget talking about this.
Had not thought about it but something to consider with any 2235 based systems.

The amp is a winner with dsp filters and limiter. Nice.

Small box too.

PS I still have the 2245s in my 4345’s doing double duty for music and HT in the new music room. Never had to turn on the 4465 yet! Might mess with a crown and EQ per the bx63 for grins.

ivica

01-25-2018, 12:10 PM

A clarification note. In part 1, E-V, Post # 2, I must add the following in order to avoid any confusion.

The paragraph where I quoted E-V concerning "With regards to Subpassband speaker protection...", this should be seen like a "by the way" note on out of LF passband filtering and how E-V suggests to determine such filter's frequency on low-frequency enclosures in general (i.e. 0.8 times Fb or box tuning frequency). This is NOT part of the Step-Down process, because the way the 6 db boost (and cut) filter is designed it already includes subpassband filtering at 12 db/oct., In addition to equalization. No requirement for redundancy then. I should have put that paragraph at the end of my E-V text as a BTW note.

In a spec sheet's section on subpassband speaker protection, E-V mentions "The step-down equalization described in the Step-Down section provides the required protection."

However, In part 3, Stepping-down with a regular equalizer, post # 4, the need for a subpassband filter remains relevant...

Richard

Hi RMC,

Thank You for your explanations about the application of bass speakers in the smaller box and active EQ.
Generally speaking, almost any speaker can be EQ in order to get the most from it, but I am not sure that the acoustical signature of the speakers with such EQ and the other without it that has 'native' better response would be the same. I am sure that almost any cheaper bass driver from say Asia that can be EQ would sound the same as say JBL 2269H , 2231A , 2245H, without EQ in the proper tuned box, especially if it would be used for the home listening conditions, where usually not more then 10W of power from the amp has to be 'delivered'.
My experience with EQ-ed LF drivers would not produce the same feeling to me while listening the music, as not EQ-ed properly 'loaded' previously mentioned JBL bass drivers, but I can imagine that the other people would have opposite conclusion.

regards
ivica

RMC

01-25-2018, 04:32 PM

Hi Ivica,

Your post is an interesting one. And I DON'T necessarily disagree with it. However, no time now since I'm writing another text on cone excursion in step-down mode that I would like to post tonight. But I will come back to your ideas in the near future. There is also a lot more info to come from me on "step-down" mode that I need to finish writing (e.g. real applications), including curious stuff or disagreements I may have. See you later.

Richard

Ian Mackenzie

01-25-2018, 04:42 PM

Hi Richard,

Have you previously heard the EV interface A model with the 8 inch woofer and 12 inch Passive Radiator that used the step down equalisation?

I recall it had un characteristically deep bass for a modest enclosure.

EV were the forerunners in the application of T/L parameters in the 1970’s.

In relation to your prior posts concerning EVs approach to assisted alignments l post a link here to the EV interface A Equaliser Owners Manual. The manual is quite comprehensive and covers topics including set up and placement and amplifier power recommendations. Moreover the manual provides insights to the peculiarities of implementing an assisted bass alignment for the consumer.

.
https://electrovoice.com/binary/Interface%20A%20Owners%20Manual.pdf

Robh3606

01-25-2018, 07:51 PM

Hello Richard

Thanks for the simulation in post # 11. A few things aren't clear to me.

What are the boosting filter parameters you applied (frequency, amplitude, and Q or bandwidth) ?
Any LF subpassband filtering applied ?

The Bx-63 parameters, the software allows you options where you can duplicate what it does.

On the bottom graph you have TWO response curves (orange and red). But on the top graph I see THREE cone excursion curves ! (two orange at Fb and one red). The orange curves are typical shape of cone travel in a vented box. However, the red excursion curve, looking like a pair of boobs, isn't typical for a vented box...

Ignore the double orange curves I was doing a quick sim and forgot to add fill to the box. The bottom line is that is a typical curve for an unassisted reflex box. The red curve is the important one as there is no free lunch using EQ. You have to remember that the peak 6db of EQ is applied at resonance where the cone movement is minimal. So you have a 4X the power applied with the associated increase in cone displacement. So you have the minimum at resonance and humps on either side.

Finally, I notice on the red excursion curve that the right hand bump is at almost 8mm @35 hz, Xmax being 8.5 mm, and the left hand bump, around 20 hz, about 7+ mm, for the same input power but with even lower frequency! Effect of subpassband filtering ?

Well that is where the 12 db slope comes in to "protect" the driver

Rob:)

RMC

01-25-2018, 10:02 PM

CONE EXCURSION

Hi Robh,

I think I found the explanation for the non-conventional looking, two mountain shape, red excursion curve compared to the conventional curve(s) with no EQ in Post # 11. And why the output at 35 hz reaches almost Xmax sooner than the output at 20 hz or so, which seems unusual since the deeper bass = the more cone travel normally.

In the extensive E-V Step-Down documentation/applications I have, I don't recall ever seeing a cone excursion graph (same for JBL Kramer/Timbers 1983 article), though one can get some idea by looking at LF Maximum Acoustic Output graph (E-V) or table (Kramer/Timbers article) for different box/driver duo (spl vs frequency). Because LF drivers are thermally or excursion limited:

"The curve which follows shows the system's low frequency maximum acoustic power output versus frequency. The maximum output is limited by either (1) the thermal power handling capacity of the speaker, or (2) the speaker's maximum linear cone excursion capabilities, whichever occurs first." ("TL 606 Builders plans Bass box" E-V document (form # 1545-846). Kramer/Timbers have a similar mention.

If you recall in part 1 (post # 2) E-V mentioned: "In step down, the enclosure is tuned to a lower-than-normal frequency. This increases system output at the new tuning frequency and reduces output slightly in the region of original tuning."

In part 2 (post # 3) Keele said "The net effect on the system response is one-half octave extention of low-frequency response with only about 3 db less maximum acoustic power output capability in the passband."

Also, in the same "TL 606 Builders plans Bass box" document E-V writes: "Note that some 2 to 3 db of maximum output in the 60 to 90 hz range is sacrificed when the step-down mode is used." Naturally, in that specific case its at 60-90 hz while in other box/driver combinations it will vary...

There's a trade-off in "step-down" mode. In order to get deeper lows, one has to sacrifice some LF output capability a little higher in the spectrum. Since E-V clearly indicates that step-down EQ has no effect on maximum output, then this capability "loss" has to be a side-effect of lower than normal box tuning, that boost EQ does not compensate for because its applied lower.

Now, if one compares excursion curves at 35 hz or so, with and without EQ (orange VS red curves in Post 11) the trade-off or sacrifice could well explain why the higher cone travel on red vs orange curve (i.e. lower output capability in that region meaning increased cone travel).

I do believe the left Xmax bump around 20 hz on the graph (which does not exist in a conventional LF alignment) is caused by the EQ boost, therefore normal in this application.

The above sacrifice or trade-off would explain the right "mountain" approaching Xmax sooner on the red excursion curve, and I think the subpassband filtering and/or higher-order alignment dropping faster is the other reason for the left "mountain" being lower than the right one on that same red excursion curve.

Makes sense to me. Regards,

Richard

NEXT TIME ON TO BX 63/A

EDIT: Robh, I'm at post # 16 now so I have some catching-up to do tomorrow...

RMC

01-26-2018, 12:15 PM

Hi Ivica, RE POST # 16

As I mentioned I don't necessarily disagree with what you wrote. But the name of the game here is smaller cabinet. The idea came to me from another thread were a fellow wanted smaller box with comparable LF performance. In order to have a smaller box,while keeping efficiency up and distortion down, there is not a whole lot of alternatives.

Stepping-Down woofer/box tuning looks to me like an acceptable or good compromise. Its still a compromise but well worth trying. Why not perfect? Resulting response is roughly flat, there is a trade-off for lower bass in reduced output capability in the region of original box tuning, cone travel is higher in the region of original box tuning ... But at least one gets what he wanted: smaller, deeper bass box! In normal use the "penalties" are not a big deal.

As for the LF sound of these filter-assisted boxes compared to regular vented I haven't had the opportunity to compare at the same time side by side with same program material comparable speakers.

Regarding EQing responses, in the past in another thread I did mention an article discussing experiments by a bunch of Engineering guys at MIT published in High Fidelity Magazine in the late seventies from Mark F. Davis, "What's really important in loudspeaker performance". Frequency response was one of great of importance. The work of Floyd E. Toole on this matter is world-renonwed, in his book 2008 Focal press, Acoustics and Psychoacoustics..., some of his work is on Harman's Web site re subwoofer placement, in the JAES and numerous magazine articles, e.g. speaker measurements VS listener preferences, e.g. on-axis response and power response (off-axis) are important criteria. His landmark work is the reason why JBL hired him as Acoustical V. P., if my memory is right. Regards,

Richard

EDITED FOR CLARIFICATIONS PURPOSE

RMC

01-26-2018, 04:57 PM

RE iAN'S POSTS # 9 & 18

Hi Ian,

I do remember E-V's Interface A for which I probably have some stuff buried somewhere in my audio Library. Never owned it and don't remember hearing it, been way too long.

Some of Ian's links in those two posts, though interesting by title, just don't want to open on my laptop for security reasons (security certificate not valid or inappropriate says Internet Explorer)... But I have most of it already anyway, since I own a pretty good E-V and JBL Library. BTW E-V's tech sheets up to the 90's (4 pages filled) are second to none, each giving a LOT of practical info not seen elsewhere. Too bad cost cutting has reduced them to only 2 pages...

THE most interesting link in my view is the third one in post # 9 titled Scrib. This one opens but bugs on my laptop. It is the web version of the Pro Sound Facts document I have quoted from many times in the past and I have the original paper version of it from E-V. That one EVERYBODY around here should have a copy not only on their desk but also under their pillow... Its probably in itself a vented-box workings and construction course... Regards,

Richard

dn92

01-27-2018, 01:20 AM

Some of Ian's links in those two posts, though interesting by title, just don't want to open on my laptop for security reasons (security certificate not valid or inappropriate says Internet Explorer)...

Richard

Same with Firefox, mentionning that security is not properly implemented on this site.

RMC

01-27-2018, 10:32 PM

Hi Robh, (EDITED VERSION)

I don't own nor use the BX 63, so in the absence of a nice data sheet, please forgive my Columbo's work.

At least now I know why no detailed data sheet found: That's a JBL Consumer Products device, not Pro division, as written on the Technical Manual I have (Consumer tends to do more user manuals than technical data sheets). B380 Tech Manual also identifies JBL's Consumer Products Division, so again no detailed data sheet.

The BX specifications mentioned in the Tech Manual (none re high-pass filtering/EQ boost), are said to be the same for both BX 63/BX 63A, except 63 has X-over at 63 hz only and 63A has X-over at 63 to 140 hz. Therefore, I assume both use the same LF HPF/EQ and the only peak boost frequencies with Q 2 filters are 20, 30, 40hz as shown in Post # 5. At least that's the case for the 5235.

The original BX 63 (not A version) was made specifically for the Kramer/Timbers 2245H subwoofer project as mentioned in that article (see post # 1). Going through that article another time I pretty much found right and left what I was looking for re LF filter parameters. It is a 6 db peak boost underdamped (bumpy) filter, that has a Q of 2. I understand the BX 63 has three fixed-frequency filters with Q 2 as mentioned above.

And there is subpassband protection according to Robh: "Well that is where the 12 db slope comes in to "protect" the driver" (Post # 19). Kramer/Timbers mention this:"The quasi-fifth-order aligment includes a subsonic roll-off to unwanted cone motion below 20 hz."

That seems quite similar to JBL's 5235 Robh referred me to and to E-V's own thing. Now I got some stuff to work with.

in post # 11 you wrote re B380 it had 4.5 cu. ft. and tuning at 26 hz. Moreover, in post # 14 you mentioned using 2235's as B380's and added "Use the DSP in a crown amp to simulate a BX-63 so same idea..." Finally, in Post # 19 you said "You have to remember that the peak 6db of EQ is applied at resonance where the cone movement is minimal." I do know that, but.... Reading again this & above paragraphs one may notice something doesn't seem right.

(Said here with all due respect and NO intention here to show any "fault" on your part nor any insult from me, but simply to illustrate below some misconceptions about approximate B6 alignments and peak boost frequency). Moreover, I also know very well that boost at Fb is not always the case, far from it you'll see!

With a stock BX described above (boost @ 20, 30, 40 hz) or even 5235, how can one apply the boost at the 26 hz tuning frequency of a B380 or B460 for example? 30 hz is near but still a little higher than 26 hz. However, the graphs in your post # 5 show a nice 25 hz to me, middle of the road between 20 and 30 hz. Which of these two do you then choose? Looks to me JBL offered a ready-made no question solution, whereas with Keele/E-V its more choose and/or design your own.

I will come back later with numerous examples and some possible explanations on peak boost frequencies. E-V's peak boost frequencies are "all over the map" by the way, and I still believe that E-V Engineers are as smart as others.

In your particular case, if the Crown amp's DSP allows, you may determine precisely 26 hz as peak boost frequency, not with a BX? In the Kramer/Timbers article they do mention on P. 4, for their 8 cu. ft. B460, "With 6 db of boost added at 26 hz, ...", then regarding their B380 "...requires the same equalization..." (as B460) and conclude "... maximum EQ boost occurs at vent resonance, ..." (last page). So, how could they say that in view of "...Model BX 63 which was chosen for this application because it was designed specifically for the present combination of driver and enclosure." (P. 4). For these Kramer/Timbers quotes, the only explanation I may see is CUSTOM MADE BX?: "We would also like to thank D. B. Keele Jr. (JBL) for his kind assistance with the computer. His efforts made the special voltage drive of the BX 63 a reality." Unless at vent resonance isn't really "at vent resonance", but a little higher as I've seen many times on Keele/E-V stuff. (BTW, no wonder they used Keele for this considering the work he did at E-V on this matter). EDIT: Or the 30 hz BX boosting filter is in reality a 25-6 hz filter? Or if the 30 hz setting for example is really a 26 hz setting then why call it 30 hz ? Or that filter's tolerance is such that it "drifts" to 25-6 hz ? Tough question. Could be a marketing thing for wider user acceptance with common numbers such as 20, 30, 40 hz... In Post # 2 E-V said peak boost frequency within 5% tolerance provides no significant performance compromise. 26hz vs 30 hz = 4 hz, and 4hz/26hz = 15% or 4hz/30hz = 13%, and to stay in the 5% tolerance of the "advertised" filter frequency would mean 5% of 30 hz = 1.5 hz ! 0r 28.5 hz not 25-6 hz...

In the Kramer/Timbers article they say: "The equalization necessary to flatten the response ..." (P. 4) This implies response isn't flat to begin with probably due to lower than normal box tuning applied. {BTW, in the B380 Technical Manual frequency response is quoted as being: "24 hz to 70 hz (- 6 db), Thru BX 63A Crossover"}.

No mention by JBL or Robh of a normal mode Fb, then a step-down mode Fb, for the B380/B460. Kramer/Timbers modeled the B380/B460 equivalents only in step-down mode in their article. Had there been a given Fb for a usual or straight vented box, I think that Fb would have been around 30-35 hz range (likely 33-35 hz? after some simulations I've done. Otherwise, what would be the interest or real gain in taking a normal mode Fb of say 30 hz and down-tune it to 26 hz?). If that is the case, and I think its possible, then this is good news for my previous cone excursion explanation (post # 20) regarding the right hand excursion bump shown in red in Post # 11, in view of "... and reduces output slightly in the region of original tuning." (2-3 db according to E-V/Keele). EDIT: I think Robh realizes that when he wrote in Post # 19 "The red curve is the important one as there is no free lunch using EQ"

Richard

Ian Mackenzie

01-29-2018, 01:43 AM

Hi Richard,

Please find below a consolidation of information relevant to Jbl which will fill some of the gaps as pointed put in your posts.

The link to Harman and LH below is the bx63/a schematic and manual posted in a prior thread for your examination.

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/BX63%20ts.pdf
http://www.audioheritage.org/vbulletin/showthread.php?32401-BX63A-Definitive-Answers-Needed

(It’s worth pointing out that most members here who have been around a while are quite familiar with the Bx63/a and the functionality of the B460 and B380. So there is no need for me to further elaborate or a dissection of that.

Concerning your prior post the summary below is taken on full review of the article and the manuals. This should also help you join the dots.

For continuity here is a link to the article .

http://www.lansingheritage.org/images/jbl/reference/technical/1983-subs/page3.jpg

http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm

In summary the article was about 2 Quasi 5th order assisted designs using the JBL Pro 2245H and the JBL 2235H extended-bass woofers.

The article discussed 3 designs:

*B6 12 cu ft 20 hz assisted - boost 20 hz f3 21 hz (2245H)
*Quasi 5th order 8 cu ft 26 hz assisted - boost 26 hz f3 26 hz (2245H)
*Quasi 5th order 4.5 cu ft 26 hz assisted - boost 26 hz (2235H) f3 - see text in article

*Fb =boost frequency in all 3 designs

*Bx 63/a was used for both Quasi 5th
order assisted designs

*Relative response of the 26 hz tuning is -2.9 DB -37.5 hz (refer to chart in article)

*QL=7 per computer table in article

*Reference in the article was also made to an 12 cu ft unassisted design (2245H) tuned to 25 hz that is comparable to
the Quasi 5th order 8 cu ft assisted design. The trade off being box size versus amplifier power

*D.B Keele Jnr provided computer design of all 3 Quasi 5th order designs

* The article references Hoge W.J.J, Keele D.B Jnr and Small R.H

*In reference to your question of the unassisted tuning please refer to the Jbl enclosure guide in the link below.

https://www.jblpro.com/pub/manuals/enclgde.pdf

We look forward to your future posts

Robh3606

01-29-2018, 10:30 AM

The plans

Rob:)

Robh3606

01-29-2018, 06:56 PM

BX-63 Manual

Rob:)

Ian Mackenzie

01-29-2018, 07:34 PM

Hi Rob,

The 2369H looks an interesting candidate with Vas 234L , Xmax a stupid large 19mm, Qts 0.36, Fs 28

If you have time can you run the numbers in BassBox Pro?

Robh3606

01-29-2018, 09:17 PM

Hello Ian

Yeah it's a great driver! Here it is same box with and without EQ. Fb 26hZ and electrical filter 26Hz Q 1.5 power input limited to 600 watts. Power limiting makes it damn near indestructible as you won't exceed thermal limits or X-Max using the EQ. So you get 3Db more output F3 shifts down to 25Hz all in a smaller 9 Cu Ft box. Not bad!!

Rob:)

RMC

01-29-2018, 09:30 PM

Hi Ian, (RE POST # 25)

RE "Please find below a consolidation of information relevant to Jbl which will fill some of the gaps as pointed put in your posts." Sorry, but that info, which I already had AND CONSULTED before writing Post # 24, does not fill any gaps pointed in my post regarding JBL's BX 63/A story. Please read post # 24 again, and where I mentioned "That {re BX 63 filter} seems quite similar to JBL's 5235 Robh referred me to and to E-V's own thing. Now I got some stuff to work with." However, your material may be useful for members less familiar with the matter.

RE "The link to Harman and LH below is the bx63/a schematic and manual posted in a prior thread for your examination." That Harman link refers to the BX 63's Technical Manual I had and quoted from in Post # 24 and other... As for the "Answers-Needed" 2012 thread link, well Robh posted here (in Post # 5) the same BX63 curves than he did in the 2012 post (also post # 5), nothing wrong with that, but no new info. As for the other attachement Robh provided in the 2012 thread (in post # 7) "JBL Low Frequency Systems Instruction Manual", I already had the Brochure for that (i.e. "JBL Low frequency Systems B460 B380 BX 63"), and after a quick look today at that Instruction Manual (for which I thank Robh and Ian) I note its the same specs pages I already had in the Brochure, but with a lot more wording on connections, etc. Again, there's really nothing new in there about the "Step-Down" process, nor filling any gaps past or present (e.g. Boost/Cut EQ filter detailed parameters). On the latter I wrote in Post # 24 "Going through that article another time I pretty much found right and left what I was looking for re LF filter parameters."

RE "(It’s worth pointing out that most members here who have been around a while are quite familiar with the Bx63/a and the functionality of the B460 and B380. So there is no need for me to further elaborate or a dissection of that." I'd be tempted to say this one is the most amusing, since the above thread doesn't help your own cause! In the 2012 thread link, member Parisphoto says "Answers Needed", then member Rusty Jefferson requests from Robh a complete scan of the BX 63 owners manual, Robh posts the scan, Grumpy thanks Robh for the manual, Titanium Dome says "Finally, a post of the "missing manual", Parisphoto tanks Rob so much for posting the manual, Robh says "I never realized that we didn't have one somewhere on the site", Hjames adds "The missing Manual"! Thanks so much for this..." And some of these are quite senior members (2003, 2004, 2005)... So, If its as well-known as Ian implies, why this then??? I think he should have read the Thread before writing that pretention or linking to that Thread...

The cruel reality is that JBL has given no detailed specs, in its BX 63/A related information documents, on the most important part of the device, the peaking boost/cut high-pass filter, except for some left and right in the Kramer/Timbers article... As if this was a secret, contrary to E-V giving so much info its almost overwhelming!

RE "Concerning your prior post the summary below is taken on full review of the article and the manuals. This should also help you join the dots. For continuity here is a link to the article" I've had the original Kramer/Timbers article since it was published in Audio Magazine in august 1983. As mentioned previously, I have read it again recently and also checked again some things in it before writing my last post (# 24) in which I quoted many times from it, however I refered to it as the Krame/Timbers article since these are the two authors. As I said here before, I did find in it most of boost/cut filter parameters, but it DOES NOT help "join the dots" as you say. So, your summary of that article may be more helpful to others than me.

RE "*In reference to your question of the unassisted tuning please refer to the Jbl enclosure guide in the link below." This issue was not really a question if you look at it, but more a tentative answer to an unknown fact (i.e. a possible normal mode Fb for B380 enclosure). The "JBL Pro Enclosure Guide" I've had in my laptop for quite a few years and did check it for the 2235H before writing post # 24. The example didn't appear optimal to me. That's why I made some quick simulations of my own as reported in post # 24. The proposed boxes in the Enclosure Guide are more "quick suggestions" or "rule-of-thumb boxes" to help novice speaker builders. They're not necessarily best, optimal or made-to-measure to each driver. This can easily be assessed by looking at the groupings or driver categories and more importantly what's in each of those with their own T/S. More like a "fit the driver in a box size group", instead of an optimal design or "made-to-measure box" considering each driver's particular parameters. In that specific 2235H case, the 5 cu. ft./ 30 hz tuning box suggested not only didn't match the B380, but also it didn't appear to match with the right hand bump in Robh's excursion curve (post # 5). "One size (doesn't) fits all" in my book.

As you probably know already, I tend to do my homework before posting. Even during and after...

Richard

Ian Mackenzie

01-29-2018, 10:14 PM

Hi Richard,

I spent some time to summarise the article as you omitted factual information relevant to Jbl forum members.

My intent was to provide a clear view of the article.

My feedback and opinion;

You omitted key facts concerning the article making the thread impossible to follow and you appear very confused in your postings.

I asked my wife could she understand your posts?
The response “what is that?”

Can you please structure your points like an educated adult so we can understand the purpose of your posts.

Enough said

Lee in Montreal

01-29-2018, 11:06 PM

Wondering where all this will lead us... Any build or projet we can expect to see?

Ian Mackenzie

01-29-2018, 11:32 PM

Hi Lee

Good point

Hence my request to Rob for some relevance and benefit to our forum member on the 2269 woofer as an example .

We all know the B380 and B460. The w1500 is NLA

So it means something useful as in a modern obtainable Jbl driver with decent Xmax and power handling.

That is a plus if we can make use of it.

As for the Ev step down or the Keele b6, it’s not new or a biggie and frankly the math behind it is mundane.

BassBox Pro can spit out what we need with Robs skills.

Only a few manufacturers did anything with B6 as a step down for a main full range system (domestic) and that was before HT subs became popular.

IMHO I don’t see the point unless designing a new Jbl sub as a project or a group buy

Lee in Montreal

01-30-2018, 12:59 AM

Wanna reduce your box size by half? Then simply fit two woofers in the same box half the usual size in isobaric configuration and obviously feed the box with twice the power. If the goal is to please the lady of the house or your "life partner" with a smaller bass box, then consider the job done. I feel that this kind of topic gets sterile pretty quickly if it doesn't end up with an application. ;-)

Ian Mackenzie

01-30-2018, 01:15 AM

Hi Lee,

Totally and nice to see you posting in this thread.

The isobaric would be one mean sub with a big crown amp hanging off it.

Unless you have dedicated man “cave “ the WAF is a barrier to execution.

I still recall watching years ago a B460 suck the life out of a 250 watt amp and it shut down.

This stuff is fun

Robh3606

01-30-2018, 02:01 PM

Just to be complete here is a 2235 set-up for extended bass vs a B380 Yeah doing this with the newer drivers makes more sense especially with the availability of cone kits becoming questionable

Rob:)

RMC

01-30-2018, 05:25 PM

Hi Robh, (RE POSTS # 26, 27)

Thanks for posting the enlarged plans, which include a little more details, response curves and data of the 12 cu. ft. box. Kramer/Timbers do refer to that box in their article, first as a classic sixth-order alignment (P. 4), then in "Alternative Designs" on P. 6 along with smaller size plans shown. However, your post adds the response curves for these designs as well as the computer generated tables of performance. Not really the box-size for me though.

I tend to think one has to have endless space (I don't have), be pretty fanatic or really "switched-on bass" as John Hoge titled his 1976 subwoofer article (21 cu. ft./almost 600 liters!), especially when considering GROSS/NET volumes involved...

In the near future, I will be covering in step-down stuff, a commercial E-V box of 76 cu. ft./net weight of 550 lbs !! , 8 ft high, 4 ft wide, 32 in. deep. Driver originally presented for "home" use if I'm correct. Old enough to remember? I do... Try to get that into a somewhat normal living room!

As for the BX 63 Instruction Manual in post # 27, thanks for that too I saved it on hard disk as I do for all JBL/E-V stuff of interest. After looking at that manual, I note it also does not address the unexplained "loose ends" in JBL's own "step-down" story. I'll just have to "play it by ear" as they say, when time comes to provide some credible or logical explanations on some of the issues involved. Like I tried to do in post # 24 and others. Regards,

Richard

RMC

01-30-2018, 05:26 PM

RE POSTS 31-35 I WILL LIMIT MY COMMENTS TO THE FIRST PARAGRAPH:

Well, look who's talking. Blaming the "messenger" when you can't contradict the facts, the usual. Then Ian and Lee should do themselves a favor and look elsewhere or start their own Isobarik configuration thread. This would alleviate their "suffering" in reading or following this one it seems, which they're not obliged to do. Then we'll see which thread is more confused. Purpose? Very well mentioned in the first paragraph of the Intro (post # 1), and since nothing was mentioned about it leading to a specific project box, you might as well turn the page and leave now. P.S. I don't need to use my wife as an excuse to desperately try to sustain my writings, nor to defend myself...

For others, during spare time i'm in the process of compiling the large amount of applications data to be presented here, in a few installments, regarding E-V's own step-down mode applications as I mentioned in post # 24, and considering what I then said "E-V's peak boost frequencies are "all over the map"...". In APPROXIMATE B6 alignments (JBL's 12 cu. ft. assisted box was called in the article a CLASSIC 6th order alignment), the "beauty" is the peak boost filter does not necessarily have to be precisely at Fb, contrary to what JBL SEEMS to have done in its modelings (though there appears to be some unexplained "looses ends" in their method/application, as mentioned in post # 24, that other members haven't yet tried to explain logically). Naturally, there are possible reasons and consequences for E-V's frequency choices some > 5% tolerance! (e.g. driver capability, excursion, distortion?) which we'll try to address, in the absence of clear explanations found.

For those who may think I'm too hard on JBL and that I may be nothing more than an E-V fan, wait they'll get their kick in the butt too... (starting right here with the above-mentioned "some > 5% tolerance! " which is THEIR number re peak boost being sufficiently close to step-down Fb to provide no significant performance compromise...)

Richard

RMC

01-30-2018, 09:32 PM

Hi Robh, RE POSTS # 29 & 36

Had a quick look at these posts. Seems to me you're being unfair to 2235H in that comparison. I don't own it so have no interest in defending it. But in all fairness for the driver one must compare apples with apples as you have done with 2269. In the 2269 comparison same box size 8.8 cu. ft. is used and same QL number. However, in the 2235 comparison one box is 7.2 cu. ft/Fb 22 hz and the other box is 4.5 cu. ft. with no QL number given. In the former much larger box with pretty low tuning this is a scenario where the 2235 is destined to run-out of steam anyway (being overstretched), in my view. So the dices seem to be loaded against it... It would appear more fair to do as in the 2269 case, meaning same box size in 2235 comparisons, along with same QL, and a more acceptable Fb around low 30's for unassisted box. Regards,

Richard

RMC

01-31-2018, 10:14 PM

Going back in some JBL documents to check some wording this time, instead of specs pages, I think I've found the "missing link" to make this BX 63/63A usage thing logical here regarding "Step-Down Mode "VS B380/B460, 12 cu. ft. filter assisted box in Kramer/Timbers article (plus large size plans by Robh in this thread), 5233A, 5234A and 5235 crossovers. Lets sort out that below.

The BX 63/A is really a dedicated "single usage" device for B380/B460 original speakers (and exact clones too!). This is revealed by the following quotes:

"The response of the BX 63 has been specified by computer for the B460 and B380... Any other network considered for use with either system should exactly duplicate this response curve. Beyond its unique suitability as a dividing network for the B460 and B380, the BX 63..." (JBL, Low Frequency Systems, B460/ B380/BX 63, P. 3, Document LFS/ 5-83). BTW that doc. date is pretty consistent with that of the Kramer/Timbers article considering normal writing/publishing delays. These quotes are pretty clear.

Now, on to the 12 cu. ft. filter assisted box. The above stock BX could not have been used for that box's 20 hz lower tuning, since the BX's peak boost frequency is at 26 hz, as mentioned in the Kramer/Timbers article and also in graphs posted by Robh here in post # 5.

This is why in post # 24 I wrote: "the only explanation I may see is CUSTOM MADE BX?: "We would also like to thank D. B. Keele Jr. (JBL) for his kind assistance with the computer. His efforts made the special voltage drive of the BX 63 a reality." I purposely underlined the word "special", since Kramer/Timbers had already mentioned "...Model BX 63 which was chosen for this application because it was designed specifically for the present combination of driver and enclosure." That application and present combination of driver and enclosure was the B460 equivalent they presented extensively, but later in the article they added other offerings like the B380 equivalent that "requires the same equalization" as they said (P. 7).

The stock BX 63 they already had for their "B460" project box, so nothing special there. However, I'm pretty sure from the above what D. B. Keele (then working for JBL) did is custom-design a "special", though similar, filter for the 12 cu. ft. box with a peak boost at 20 hz this time (P.6) instead of 26 hz. That 20 hz filter is also special in the sense that, to my knowledge, it has not been commercially available from JBL like the usual 26 hz BX. I didn't find any trace of it, other than in the Kramer/timbers article. That should put the 20 hz filter issue to rest, except for what should I do if I want a JBL 20 hz peak boost filter? The 5235 crossover does have such a filter, as well as the 5234A, both being two-channel devices, and if I remember correctly the one-channel 5233A may also have such a filter.

This leaves a few other applications issues to discuss briefly. Can the BX 63 be used with other speakers than those mentioned above? Possibly yes, if the step-down box tuning frequency is close to the BX peak boost frequency and the woofer has enough LF "steam". Close means Fb equal to or a bit LOWER than BX 26 hz which implies the latter will be equal to or a bit HIGHER than Fb. Its much preferable to avoid having the BX boost at less than box Fb since a vented box starts unloading the driver below that frequency, with increased excursion/distortion, imagine if you add a bass boost below Fb on top of that, its a recipe for driver damage. {In the forthcoming application examples that I have from Electro-voice there are two similar boxes in which E-V applied the peak boost a bit (3 hz) below Fb! But these are Engineer designed with computer modeling so they know what they are doing}.

As for 5235/5234A such applications, the peak boost frequencies are at 20, 30, 40 hz which seems convenient for a number of applications, as long as you play it safe, and keep boost frequency equal to or a little ABOVE box Fb in your own applications... A little above Fb has minor lesser deep bass consequenses, which are far better than the other way around with a busted driver...

Richard

EDITED FOR MINOR TYPO CORRECTIONS

Robh3606

02-01-2018, 11:06 AM

Can the BX 63 be used with other speakers than those mentioned above? Possibly yes,

With DSP you can borough the idea from it and adjust Q and Frequency as required for a specific application or just use DSP to mimic a BX-63 if the requirements are the same. DSP has essentially made any of these dedicated analog boxes obsolete. Especially as far as subwoofer applications are concerned as many contain multiple EQ filters for adjusting the in room response to deal with primary room mode issues.

Rob:)

Lee in Montreal

02-01-2018, 11:18 AM

The Linkwitz Q transformer can indeed now be easily applied (and modified) in the digital domain. Rendering most of the "old boxes" totally obsolete except to collectors. I sold my old Kef Kube 200 Linkwitz Q transformer as soon as I got my DSP many years ago.

https://www.minidsp.com/applications/advanced-tools/linkwitz-transform

Ian Mackenzie

02-01-2018, 01:45 PM

The Bx63 can be modified to other F and Q but would require invasive modifications to change out parts on the pcb. They are so rare why would you do it?

Probably not the easiest approach

If analogue is your only option and you can solder this link could help

http://www.ska-audio.com/diy/BassXt.html

(This engineer previously worked for Mark Levinson and the pcbs are first rate)

I agree the dsp particularly if in the power amp is a far more flexible and easier solution for diy

Below is the 1200 watt Dayton amp with dsp.

http://www.daytonaudio.com/index.php/spa1200dsp-1200w-subwoofer-amplifier-wl-dsp.html

RMC

02-01-2018, 05:44 PM

Even though DSP in your Crown amp was mentioned in earlier post(s), it remains an actual and relevant topic.

No doubt DSP is the new or modern way to fly. Agreed, nobody in his right mind can deny that. However, to me this doesn't automatically mean older stuff suddently all disappeared or was scrapped, based on what I see here in some threads. There's still quite an interest from folks for older JBL gear whatever it may be, even non-collectors. Right or wrong, I do sense some nostalgia right and left... I tend to think there are probably still quite a few BX/5234A/5235/etc. out there, or being looked after.

RE BX 63, 5234A, 5235 and/or many other examples, obsolete? Yes and no. Certainly NLA in many cases, but still sought by some and for the many who happen to have one in good condition it can still continue to do the job right even in a changing world to DSP. Am I getting rid of, for example, my original analog Mackie mixers in nice condition, from the time Greg Mackie made them (20+ years!), simply because the new trend is to digital mixers? NFW (sorry for that). Not until they die on me... The newer "el cheapos" are not worth that.

Changing for changing, or because its more "fashionable" ? The newer DSP equipment does offer more flexibility in many cases, which I happen to like, but as for quality, reliability and "built like a tank" I'm attached to, its very questionable in this world of cheap and disposable stuff... e.g. my oldest EQ was purchased in 1979 and still works like new. The "damn" thing just don't want to die! I only cleaned once or twice an in/out switch with Caig's Deoxit in almost 40 years of ownership! Should I dump it just for the sake of it, or because I already have a replacement model on the radar? If it does the job right, what's the purpose?

Lee mentioned having sold his Kef stuff, no problem with that re flexibility, but I understand on the other side of the equation there was a buyer for that which logically wanted it to use it. Hence my point in the first paragraph. I'm not against DSP at all, nor convinced that DSP suddently made all older boxes only good for the dumpster, considering what I see around this Web site. When a piece of equipment dies on me or is really obsolete (e.g. incompatible, etc.), for sure newer technology will replace it, and that's OK.

EDIT: I seem to recall that member BMWCCA mentioned in the past on this site having Crown D series amps for some 35 years. Should he replace them with newer digital amps with or without DSP? Tough call isn't it? Cost/benefit approach then? Still tough. I also remember reading on Bryston's web site some time ago that their 20 year warranty did not apply to digital equipment since they didn't have enough reliability experience, data or maybe faith in it? Can't remember the exact words used. Add to that today's lowest-cost manufacturing practices in general, its scary.

Bottom line, analog or DSP the LF peak-boost frequency rules remain the same!

Richard

P.S. To Robh, out of curiosity, when you modeled the 2269 in Bass Box (post # 29) you used filter Q 1.5 instead of the usual Q 2 for step-down filter. Any specific reason, like driver or software limitations?

Robh3606

02-01-2018, 08:12 PM

P.S. To Robh, out of curiosity, when you modeled the 2269 in Bass Box (post # 29) you used filter Q 1.5 instead of the usual Q 2 for step-down filter. Any specific reason, like driver or software limitations?

Because I got too much of a peak @ 26 Hz with a Q of 2. Better overall response curve using 1.5. In a modern DSP set up you just type in the Q you want. For the older analog boxes you need to change out parts to make the mods. For what's it's worth I use a BX-63A on my stereo B380's and use the DSP in my amp for my LFE subs. I also use older PS 200 and 400 crown amps in my HT set-up. I have quite a mix of modern and "vintage" gear in that set-up and they all seem to play very nice together.

Rob:)

RMC

02-01-2018, 09:05 PM

Answer makes sense. Trying to think why Kramer/Timbers, Keele and E-V never mentioned this issue as I recall. Maybe related specifically to driver or driver category used (e.g.2269)?

Richard

Ian Mackenzie

02-02-2018, 03:04 PM

After reading the EV XEQ-2 Manual and the Keele paper below l think careful attention needs to be paid to use of the table 1 Fpk/Fs ratio (6 dB Q=2) for boost frequency and the formulas 7 & 8 for Fb and Vb respectively.

As an example interpolation of values of Qt for the Jbl 2269 (0.36) from Table 1 and equations 7&8 yields

Fb = 23.3 hertz
Vb = 125L plus 20% for box losses = 150L (fill =none)
Fpk/Fs = 25 hertz (6 dB Q=2)
QL=7 (note overvolume added)

These are the theoretical values.
Practical implementation would suggest checking the driver T/S after Break in before design of Fb and Vb.
The ports have considerable length and will increase the overall gross volume overall as will substantial bracing and driver Vd.

For a continuum of values Keele refers to equations 4&6. This could be conveniently arranged in Excel.

What this means is an accurate implementation of the classic B6 alignment with your woofer at home will require some home work before making saw dust.

I would also stress the importance of Xmax of your driver, power handing and a high pass filter before getting too excited. As we know recone kits are in limited supply.

Most vintage Jbl woofers have a relatively small Xmax of 4-7 mm compared to the 19 mm of the 2269.

Back to the Jbl 2269 l estimate the gross internal volume to be in the order of 190-200 L or 7 cu ft3. No free lunch here if you were hoping for a compact Sub.

As a preliminary exercise l created an boost at 25 hertz in Bassbox 5.1 using the manual acoustic environment that can be added to the box curve. Note l did not incorporate the high pass filter. The curve is below. The trade off being amplifier powerversus box size versus bass extension

The total acoustic power output is impressive being a frightening 132 dB at thermal power limit.

The curve is small signal parameters and it would be interesting to evaluate the power power compression at a maximum power.

I don’t doubt BassBox Pro will provide a more accurate simulation

http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(1975-07%20AES%20Published)%20-%20New%20Set%20of%20VB%20Alignments.pdf

Robh3606

02-02-2018, 08:02 PM

Lee in Montreal

02-02-2018, 08:34 PM

Ian Mackenzie

02-02-2018, 08:44 PM

As a matter of relevance that leaves the more recent soa drivers for those who have them like the 2216, 1500AL ect?

No doubt for HT diy subs it has merit but only with large excursion drivers like the 2245, 2242, 2266 or 2269

Lee in Montreal

02-02-2018, 09:00 PM

A 2245 has ample bottom octave presence. I don't think it needs a Q transformer. ;-)

Ian Mackenzie

02-02-2018, 09:18 PM

Correct,

I think the standout virtue of the 2245 is its linearity.

The authority makes the music sound real.

The question remains is there a relevant b6 application for Lansing forum members?

The 12 inch systems have Xmax limitations.

A number of people have the 4345 and the b460 as a sub and some have the 2242 as a sub.

RMC

02-02-2018, 10:03 PM

Hi Robh,

I looked around quickly to try to understand what may be the cause of the Q 2 filter generating a too peaky LF response when you modeled the 2269 driver.

I've noticed that JBL 226x series woofers tend to have higher Qts than most older generation JBL drivers in the 22 series (except a few, e.g. 2241). The 2269H/G in particular has a Qts of 0.36/0.39 which may be part of the explanation regarding response curve being too peaky in step-down mode with filter Q 2.

Also, I've found a couple of JBL boxes using the 2269: ASB 7118 and MD7. The first one has some interest being a vented-box, whereas the second one has less since its a horn-loaded Disco enclosure.

No net ASB 7118 box size or tuning frequency is given in the spec sheet, so I'm walking on thin ice. From box outside dimensions I calculated 8.79 cu. ft., naturally less than that for a real Vb. Interestingly though, in half-space loading and even for full space loading(!) the frequency response shows a bumped curve of about 2-3 db in the 45-50 hz range. Either the box was really designed to bump (?) or its a driver effect.

Bullock (1) did cover the issue of driver Qts VS frequency response, box size and transient response. He mentions "relative box size increases with total Q"(Qts), "Responses are either flat ... and correspond to low Qt values, or non flat ... and call for a large Qt value." He adds that because of this driver will almost always determine if response is flat or not. In summarizing driver choice, he states when choosing low Qt driver one can get flat alignment and best transient response, while high Qt driver may allow realization of a very low cut-off frequency (which appears to be the case with the 2269). But he mentioned many times that transient response deteriorates with increasing Qt.

I also checked Qts number for a sample of 10 E-V LF drivers used in step-down boxes and ALL had Qts of 0.16 to 0.28, except one at 0.34 which showed a predicted LF response with a very slight "bump" in typical enclosure. It seems to me there's some correlation between a normal/lower Qts number and flat bass, whereas higher Qts drivers tend to show ripple in response (peak or dip). Driver bass accent plus Q 2 boosting filter might well explain the "too much of a peak"?.

In my book, the above looks like a feasible explanation for the above-mentioned issue. If so, it would be something to watch for when doing step-down with higher Qts drivers. Newer generation "Super Woofers" may render usage of traditional LF boosting tools having fixed Q 2 filter (e.g. BX 63/5234A/5235, etc.) more "touchy" to use with these specific drivers. Only a proper modeling in each case will tell for sure. Regards,

Richard

(1) Robert M. Bullock, Bullock on boxes, 1991. Of particular interest on these issues are: P. 19 center col., P. 31 right col., P. 34 left col.; See also P. 5 center col., P. 6 center col. and P. 7 left col.

EDIT for clarification purposes: The 10 E-V LF drivers used in step-down boxes are in fact 11. And they include 12"/15"/18" Pro drivers. The 11th one has a Qts of 0.297 and its predicted LF response in typical enclosure also shows no frequency response bump in step-down mode with Q 2 filter.

Even more Interesting, is the fact the eleven drivers have an Xmax number in the range of 3.3 mm to 6.4 mm (more for Xlim), according to their data sheet... This shows step-down/peak boost may also be used in a beneficial way, even with somewhat limited Xmax drivers. Especially considering the boost is applied at or near the new tuning frequency where vent help is important and cone excursion reduced, plus the 12 db/oct. roll-off at high-pass end of the filter, combined with the box natural roll-off below Fb, protect the woofer from too early overexcursion (up to a point). It all depends on what one is expecting from the speaker in terms of maximum LF acoustical level, particularly in a normal home set-up.

Ian Mackenzie

02-03-2018, 03:00 AM

Hi Rob

I also found the Q=2 way too much in your simulation with 8.6 cuft3.

It caused peaking regardless of fb at the volume.

However, if one follows and understands the Keeles paper that box volume is simply too large.

In bassbox extended alignment Box volume is 6.9 cu ft3, Fb is 26.3 and F3. 31.4 hertz
Adding Q=2 at 26 hertz caused peaking

In other words that selection of Vb and Fn does not require boost

The maximal flat QB3 alignments only requires 4.8 cu ft3 where FB is 29.5 F3 is 35.5
Adding Q=2 at 26 hertz caused peaking

Fb is too high.

However reducing the Fb to 23.3 hertz , Vb to 5.3 cuft3 and boost at 25 hertz per my prior posted b6 alignment caused only +.2 dB positive ripple where F3 is 24.8 hertz (following Keeles equations and Fpk/Fs ratio in Table 1.

There’s no guess work required.

Back to the question of relevance new Jbl sub build would seem the only application

Keeles paper explains the relationship of compliance and Qt

Robh3606

02-03-2018, 08:41 AM

Hello Ian

I also found the Q=2 way too much in your simulation with 8.6 cuft3.

Are you talking the 2269? I saw the peak in the sim and dropped the Q to 1.5 also that was what the program came up with using the extended bass tuning. I didn't try to modify it. Do you get a different box size and tuning using that option??

Rob :)

Ian Mackenzie

02-03-2018, 01:17 PM

Yes 2269H

It said 6.9 cu ft in extended bass tuning (bassbox v 5.1) (no fill QL=7)

Ian Mackenzie

02-03-2018, 01:38 PM

I think (7.00am-too early) l worked it out.

It could be you left the box the same volume after the 2245 sim so you adjusted the Q of the boost to 1.5.

(Could be my data is invalid?)

Similar result but the overall box size is bigger than need be.

I think the “thinking “ behind Keeles formula is a trade off of amplifier power versus box size.

Ian Mackenzie

02-05-2018, 03:36 AM

Hello Ian

You bring up a very good point on the older vintage drivers, attached is a sim with the 2231 vs 2235 in extended bass response alignment. If you look at the box size Fb it's remarkably similar except for Excursion and power handling. These older drivers with limited X max are poor candidates for any kind of boost. The 2231 runs into trouble with 100 watts input in a large reflex box. Forget about adding any additional power.

Rob:)

Hi Rob,

Attached is a data cut sheet on the EV TL 3512.

This document clearly illustrates your point with curves that highlight small versus large signal output and maximum output in "normal" and "step down mode."

A picture speaks a thousand words.

The idea is neat with a small signal but when compared to the large signal in step down mode there is a significant differential in output below 100 hertz.

The output below 100 hertz is very much dependant on the Xmax of the driver and we reiterate that with the older vintage JBL drivers with Xmax 4-7mm (particularly 12 inch or smaller ) step down is not appropriate. Your driver may be a high sensitivity type or a woofer in a bookshelf system - the same issue still applies.

If you seek loud deep bass consider a dedicated JBL (or 3rd party) brand subwoofer.

The attachments are purely to illustrate the point and mean no adverse criticism of the TH3512 system.

Ian Mackenzie

02-05-2018, 08:41 PM

Here is a fitting bit of trivia that was attributable to D. Broadus "Don" Keele, Jr.

https://en.m.wikipedia.org/wiki/Sensurround

Scroll down to development

“pseudorandom noise generator, designed by D. Broadus "Don" Keele, Jr.

There’s no doubt D.B Keele is an innovator when it comes to loudspeakers.

I initially thought it was EV but no it was Cerwin-Vega woofers

They would have been an interesting driver.

RMC

02-07-2018, 07:58 PM

As promised in an earlier post, here is the first part of some E-V real life Step-Down tuning applications. This shows, AMONG OTHER THINGS, how much this can vary in approximate B6 alignments as E-V says, contrary to classic B6.

In the relevant Pro Sound Facts 19 page Bulletin, E-V mentions having modeled, in both normal and step-down modes, 34 single driver systems and 28 dual-driver systems for the speaker builder (though I counted only 23 in the dual-driver category). Sort of "modeled many for every taste", though some are questionable.

Considering the large number (57) of box/driver combinations, in this speaker builder group, I will limit this presentation to the ones of interest (i.e. in step-down mode only) and use statistical presentation here to show the results since that still leaves 28 driver/box duos: 17 for single woofer and 11 for dual-driver enclosures. These do include 12"/15"/18" drivers. Probable explanations are given for "unusual" data, since none are given by E-V.

SPEAKER BUILDER BOXES DESIGNED BY E-V

BOOST FREQUENCY (Faux) COMPARED TO BOX TUNING (Fb)

SINGLE WOOFER (17 boxes)

* - 3 hz, 1 box, 12" wooder, box smaller than typical, Xmax 4.1 mm; < Fb more risky, must know what you do

* + or - 0 hz (Fb), 6 boxes, similar to classic B6

* + 1 hz, 1 box, same box size/Fb as + 3 hz below, but with different more capable LF driver

* + 2 hz, 6 boxes, similar to Keele's step-down examples at + 2 hz above Fb

* + 3 hz, 1 box, box larger (14.3 cu.ft.) than typically recommended for driver

* + 5 hz, 1 box, very low Qts 0.16 driver, box larger than typical rec., low 25 hz Fb, driver overstretched?

* + 7 hz, 1 box, box much larger (20.4 cu.ft!) than recommended & tuning too low (18 hz!) re driver capability

DOUBLE WOOFER (11 boxes)

* - 3 hz, 1 box, similar to above -3hz box except larger Vb, same comments as above apply here

* + or - 0 hz (Fb), 4 boxes, larger box, same comment as above applies here

* + 2 hz, 6 boxes, larger box, same comment as above applies here

* Note 1: the above +3hz single box now in dual version shows 1hz closer boost to Fb in a 13.9 cu.ft. box, F3 up by 8hz

* Note 2: the above +5hz single box now in dual version shows closer (+2hz) boost to Fb in larger 1.4 X box Vb, F3 up by 1 hz

* Note 3: the above +7hz single box now in dual version shows much closer (+2hz) boost to Fb, 19.9 cu.ft. box, F3 up by 3 hz

As can be seen, the majority of peak-boost frequencies are at Fb or a little higher (+2hz) in both single (12/17) and in double (10/11) woofer boxes.

BTW the average down-tuned Fb for all boxes (single and double) is 32 hz. And the average step-down F3 for the same group is 33.7 hz.

E-V appears to be adjusting or compensating on Faux when driver isn't a natural best fit for the box size/Fb.

In a number of cases the peak-boost frequency (Faux) is higher than usual (Fb or +2hz) either to minimize the trade-off (maximum output loss in the vicinity of cabinet's original Fb), or to reduce driver excursion getting closer to Xmax... My comments follow in the next post.

Richard

RMC

02-07-2018, 08:03 PM

The span of peak-boost frequencies seen in the data goes from - 3 hz below Fb to + 7 hz above Fb, which represents a sizable 10 hz spread! The reason for that may very well be woofer capability related. This also tends to demonstrate there is some possible fiddle with this peak-boost frequency. However, then one may not get 100% possible LF extension (when going more + hz than normal), but may still reap acceptable benefits from it.

Also, remember the speaker builder is allowed a 5% tolerance of the recommended peak-boost frequency in order "to provide no significant performance compromise." (E-V)

Interestingly, double-woofer boxes have less issues compared to some single woofer ones since E-V DID NOT use the usual "double driver/double internal volume/double vent area/vent length unchanged" rule-of-thumb, to model them in duo when they had trouble singly. A few singles with abusively large boxes/low tuning show driver "running out of steam": e.g. 1 X 18", Qts 0.27, 20.4 cu.ft., Fb 18 hz = begging for trouble VS same 2 X 18", 19.9 cu.ft., Fb 25 hz = making more sense and improved driver performance. So they did use smaller cabinets than rule-of-thumb for some two-driver boxes, with little higher bass F3, but did so mostly for higher output level capability in my view.

BTW, JBL also has some questionable normal mode recommended box volumes for some drivers, such as 2205H, 2220H, etc., even well after T/S science was known, like E-V does.

Box size and tuning VS driver ability have to make sense to begin with, regardless of manufacturer name. The best way to insure that is to model it appropriately in speaker design software, then look at spl vs Xmax. Suits you?

Nevertheless, boxes with less than twice Vb for double-woofer could still be an option to consider when lowest bass possible isn't the main criterion, but rather a reasonable box size having more LF SPL with less excursion penalty, or when a single bass cabinet with two woofers, reasonable size and logical step-down would do the job.

In reviewing a dozen + E-V woofers before writing this thread I noted Qts is generally < 0.30. I also found yet another driver, this time with a Qts of 0.36, which also shows a little bump in LF on step-down with filter Q 2 but a bit more peaky than the driver with Qts 0.34 mentioned in an earlier post (# 53).

In that review, more often than not, E-V drivers tend to have somewhat less cone travel capability than "equivalent" or so JBL drivers. The data is no surprise to me as I've understood long ago that JBL targets more the Premium audio market, whereas E-V seems to be more Middle audio market oriented on woofers, when considering the technological advances implicated and the important price points issues. More Xmax is usually better (if its ever going to be used) for very high level LF reproduction. LF capability also makes some JBL drivers good candidates for Step-Down mode, as well as some other brand names.

Again, It all depends on what level of LF output one is expecting for home use (usually much less than PA work) and budget. A step-down LF output level (e.g. 116 db @35 hz or 118 db @ 30 hz), or even less than that, is more than adequate for most audiophiles, those who have neighbors, no hearing loss or don't try to impress the gallery. I tend to agree, for normal everyday use, with Ivica's mention In post # 16 "... used for the home listening conditions, where usually not more then 10W of power from the amp has to be 'delivered'." When one considers a conservative 93-95 db/W/M, then 10 watts means 103-105 db already, which is pretty loud.

Other E-V speakers of interest that are/were commercially available will be covered later, some individually or in groups when convenient, also with probable explanations. Naturally, I've kept a few "rounds of ammunition" in the holster for later use.

Richard

Ian Mackenzie

02-08-2018, 11:17 PM

http://www.behringer-electric.de/files/lautsprecher/mythos_jbl/Der_Mythos_JBL/stereo_sound_story_of_jbl_english.pdf

Go to page 24

It’s an interesting account of JBL LF driver evolution

Ian Mackenzie

02-11-2018, 05:21 AM

For those interested in this topic l contacted the author of the paper below requesting clarity on the EV step down implementation.

The author kindly responded with the explanation below.

There are 3 steps:

Step 1
You just tune your vented box with two identical ports which tunes the box to a conventional 4th-order HP Butterworth alignment.

Step 2
You then cover one of the ports which drops box tuning down about one-half octave ( x 0.707 fB).

Step 3
You then EQ the response with a second-order HP filter with a Q of 2 (boost of +6 dB) at the lowered resonance. This changes the tuning to a 6th-order HP with the lowered f3 about one-half octave below the original fB.
The paper explains all this. See Figs. 2, 3, and 4.

http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(1975-07%20AES%20Published)%20-%20New%20Set%20of%20VB%20Alignments.pdf

Lee in Montreal

02-11-2018, 10:04 AM

Robh3606

02-11-2018, 01:05 PM

Hello Ian

Thanks contacting him and posting his response! Great stuff!

Rob:)

Ian Mackenzie

02-11-2018, 02:00 PM

No worries.

Don Keele was helpful and friendly.

For a practical example go to appendix 11 that covers application of a sealed, QB3 vented and the B6 alignment with a common woofer. Cross reference to equations 7 & 8 for Fb and Vb.

The far right column in Table 1 gives the ratio of Fpk /fs where Fpk is the boost frequency.

The comments concerning over volume are no biggie (box losses) and something you would have to do in the absence of modern simulation software back then.

ivica

02-17-2018, 05:49 AM

RMC

02-17-2018, 12:23 PM

RE "Interestingly", that some amount of posts on this thread have disappeared from the Forum,

I sure don't have the authority, capability nor will to remove posts here, even more so when it appears like one-sided censorship. If you remember or look at what was removed and kept its pretty evident who did it, and for what reasons... I'll leave it at that for the time being, and continue my work.

Robh3606

02-17-2018, 12:59 PM

If you remember or look at what was removed and kept its pretty evident who did it, and for what reasons... I'll leave it at that for the time being, and continue my work.

Actually to solve the mystery I removed them and in particular the blatant personal attack that started the string.

Rob:)

RMC

02-17-2018, 09:20 PM

Something maybe more "entertaining" than really practical follows. I was reading recently a Web page on E-V's history, where it was mentioned this 30" woofer was introduced in 1959. I've seen documentation on this a long time ago and was impressed by its huge size. I seem to remember reading elsewhere E-V describing it as the largest viable woofer in the world, or something like that.

The interesting aspect here is that E-V modeled and sold that huge size driver/TL series box, also for step-down mode use, even if a 30" woofer might not really need boosting filter assistance... This E-V application of the concept being with a quite unusual driver. JBL too did that with their largest 2245H woofer (Fs 20hz), In the Kramer/Timbers article: out of three 2245 boxes they modeled, two were boosting filter assisted. Plus the fourth box for which they gave info, was also filter assisted using 2235H.

When Bob Carver introduced in the seventies his high-power Phase Linear power amps, models 700 and 400 with their large VU meters, things started to change forever. The power race was on for both amps and speakers, plus it never ceased...

However, the 30W woofer remained for some time before becoming "NLA/obsolete" in the eighties I think (its certainly not on my 1991 EV price list). It was something special. For comparison purposes, the well-known JBL 2245H has a diaphragm area of 201 sq. in. In addition, a number of manufacturers like B&C, Beyma, 18 Sound and RCF still make 21" woofers, one of which is described by an authorized dealer as "features a massive 260 square inches of diaphragm surface area—nearly 40% more than an 18" driver" (Re B&C 21SW152-4 21"). Rather 30% more based on my calculation regarding the above two contenders. Still nice though.

The 30W had over 500 sq. in. of cone area according to E-V data sheet, which is almost DOUBLE that of the 21"size! This IS REALLY massive... Sure the "old dog" can't match the more recent power ratings, the ear splitting SPL's and probably not cone travel capabilities of modern drivers. As for the latter, it don't necessarily need to. Since air moving to reproduce low frequencies can be done mostly by cone size or cone travel, or a mix of both, its pretty evident the 30W does it primarily with cone size.

This driver was used mostly in E-V's Patrician home speaker system. Nonetheless, a Pro Sound TL series vented box was also made for it and the relevant specs summary gives enough info for our purpose. The two data sheets I found for the 30W (one from E-V and one from University Sound (see note 1) which was kind of E-V's commercial/installed sound division the 30W was later transfered into) do not give detailed T/S parameters, presumably because its an old woofer.

Though, I'm pretty sure E-V did measure the T/S at one point because that driver was also used in the 28 cu.ft. (800 L., 125 Kg) 1983 Patrician II loudspeaker system (a special Swiss-made! anniversary edition for... Japan market, naturally) and the brochure for this indicates "The uncompromising application of the Thiele/Small principles..." and further adds on the specs page "Type, bass reflex after Thiele/Small". Can't design one of those boxes without knowing driver T/S parameters. Not published by E-V though, as far as I could see.

Swiss-made? I assume its because E-V and Mark IV Audio (EV's owners at the time) had their European division in Switzerland, where E-V was also the main equipment sponsor for the well-known Montreux Jazz Festival held in that country. Any better IMAGE OR PERCEPTION of quality craftsmanship and precision than Swiss-made to sell it on Japanese market? I think this explains Swiss manufacturing in that particular case.

Other E-V available info of interest includes: polystyrene foam cone, Fs 15 hz, 8 ohms (surprising, in the old days many were 16 ohms), power rating 60W RMS/150W pulsed, conversion efficiency 10%, EIA sensitivity 54 db (equivalent to 101.68 db/w/m using Eargle's formula and nomograph- see note 2), no Xmax given but they say "Even at full power input, cone motion is within the linear range." Finally, the driver may have been modified over time since recommended enclosures were sealed (and ported boxes said to be neither necessary nor desirable!), and the TL 303 and Patrician II are vented boxes...

TL 303 box in the next post.

Richard

RMC

02-17-2018, 09:25 PM

The dimensions and weight of the TL 303 box make this a one-time or so placement adventure at 76 cu.ft gross internal volume (85.3 cu.ft. ext.), 8-foot high, 4-foot wide, 32 inches deep (ext.), and a net weight of 550 lb... That box was designed with ONE driver. The normal/step-down mode info follows, as well as some other, and comments.

Normal mode F3: 26 hz, step-down mode (with EQ) F3: 17.5 hz (a bit below hearing threshold). Kramer/Timbers, 12 cu.ft. assisted box, 2245H, "... resulting in a system F3 of about 21 hz."

Normal Fb: 23 hz, step-down Fb: 18 hz (same JBL box as above, step-down Fb 20 hz)

6 db peak-boost frequency: 19 hz (same JBL box as above, boost applied at 20 hz)

Efficiency half-space: 5% (in TL 303 box); 2245H: 2.10%

Usable lower limit frequency: normal 20 hz, step-down 18 hz ("System can generate one-half acoustic watt or more down to this frequency")

Usable upper limit frequency: 600 hz ("System is reasonably flat...")

Maximum SPL at 10 feet, full power: 112 db (equivalent to 121.68 db at 1m using Eargle's formula and nomograph)

There isn't a whole lot of deeper bass to gain (8.5 hz compared to normal mode) when dealing with already low numbers and mammoth size cabinet, or when compared to 2245H 12 cu.ft. assisted box (3.5hz). More for the fanatics or the show I guess. And the trade-off of smaller box with deeper bass but with 4 times power requirement isn't here, only deeper bass is. That box is definitely a curiosity from the past. I wonder how many of these they really sold VS the many fellows who built their own. The 28 cu.ft of the Patrician II (a 4-way system) makes about 50% more sense at half the weight, 67"X36"X20.7", 10 hz higher F3, but nothing indicates it can be used in step-down mode.

Richard

(1) I've used only the E-V data sheet and info here. Some University Sound spec sheet numbers are curious e.g. sensitivity rating averaged 500-5000 hz and frequency response to 1khz. Whereas E-V states rec. x-over 100 hz (as in Patrician II), and usable upper limit 600 hz.

(2) The EIA (1mw at 30 feet) sensitivity conversion to db/w/m would have given 103 db/w/m here when adding 30 db for one watt plus 19 db for one meter. The 1.3 db difference isn't a large one, but would also need to be considered in max. spl output with that method. I used the more conservative number.

Chas

02-19-2018, 10:21 AM

FWIW: I have a friend with a pair of Patricians in his living room. Trust me, those suckers move a lot of air with very little power!

RMC

02-19-2018, 12:42 PM

Hi Chas,

Thanks for the input. I do believe you. For the Patrician II the specs in the brochure I have indicate a minimum required input of... 1 watt! And the suggested amplifier power is 1.5-600 watts! I checked twice that suggested 1.5 w amp power and it IS 1.5 w. I mistakenly read initially a more usual 15 watts...

When using EIA sensitivity number and method to convert to 103 db/w/m no wonder it moves a lot of air with very little power as you say. And that makes no say of horn loading.

Lucky friend you have. There's a group of followers for that huge driver/box, many of which I've seen on the Web with their own speaker builder boxes, including some with multiple 30W drivers! Dear god help us, as they say (from the neighbors).

BTW I just found the phrase EV used to describe it (I wasn't sure of the exact wording at the beginning of my post): "the largest successful driver ever produced."

Regards,

Richard

RMC

02-28-2018, 01:07 PM

I've changed the order of presentation a little since some data stuff is not ready yet, whereas some other material is. Therefore things are presented when they are "fit to print".

A) TRADE-OFFS

There are two trade-offs when going the step-down/peak-boost way. The first one is 4 times required power for the 6 db boost in exchange for smaller cabinet with one half-octave or so deeper bass. "or so" because sometimes its a bit more or less depending on the step-down Fb and where the boost (Faux) is applied. We've seen in a previous post E-V Home built examples where this auxiliary filter frequency can vary a lot, Faux was from -3hz to +7hz compared to Fb, probably related to driver LF capabilities and box size (some too large or small, others OK).

The second trade-off is a relatively small loss of maximum acoustic output capability in the region of original box tuning frequency, in exchange for more output deeper in the bass range. In one of his "B6" examples Keele mentioned about 3 db capability loss in the passband (this was compared to a B4 alignment). In a few of it's own documents, E-V mentioned some 2 to 3 db of maximum output is sacrificed. So, to gain some output on the left side of a response curve one has to let go a little on the right side (a bit higher).

Up to now, I've seen one case only where that second trade-off yielded up to 7 db maximum acoustic output loss, likely because the driver was overstretched in the boxe's size, with too low step-down Fb of 24hz, and/or driver Xmax of 5.6 mm. Faux was applied at 29hz (+5hz compared to Fb, to compensate It seems). But it could still produce a worst case 113 db @ 33 hz and 115 db @ 28hz, which is pretty loud. Again, a matter of needs and budget.

Its important to note that E-V mentions in another document "Maximum acoustic output is theoretically reduced by the amount of equalization." Then adds, if the highest possible SPL is needed for an application then the normal mode configuration is recommended. (E-V, SEQ Step-Down Kit for Sentry 500 System, data sheet, P.2). E-V calls the resulting output a "Theoretical Low Frequency Maximum Acoustic Output", meaning its not an actual measurement, presumably as modeled by computer software, so a likely ballpark number.

More to come.

Richard

RMC

03-01-2018, 06:02 PM

B1) KEELE

Even though Keele mentions in his paper that his new alignments have coincident ("occurring together in space or time") F3, Fb and boost (Faux) frequencies, in his three modelings of "B6" alignments the boost frequency was 2-3 hz higher than Fb. I guess this is part of what makes them pseudo, or approximate B6 as E-V calls them. By Keele's own formula of EQ boosting "at 1.07 times the cutoff frquency", and elsewhere mentioning 1.07 times Fb, then Faux is destined to be a little higher than Fb. Though E-V did have some precisely at Fb, others higher/lower... Its normal for a B4 alignment to have F3 = Fb, for a QB3 it isn't.

After discussing the suitability of woofers for use in sixth-order alignments (quote in post # 3), Keele ends that paragraph with the following regarding driver Qts: "If a hump of up to 3 db is acceptable, Qt values up to 0.85 would be usable." (P. 356) In my view this confirms what I wrote in Posts # 53 and 61 regarding higher Qts drivers used in step-down mode. These will continue to perform as they do, meaning their inherent tendency to bump in LF won't suddently disappear simply because they're being used in a pseudo B6 alignment. As stated earlier, most of the drivers E-V used in step-down had Qts < 0.30, one at 0.34 and another at 0.36, as seen up to now.

In his applications (P. 356...), Keele indicates his sixth-order alignments "... are very useful when applied to two widely different classes of drivers:" "The class 1 driver used in a vented-box system is found to fit [ later he writes "roughly fit" P. 358] the quasi third-order Butterworth alignments of Thiele (QB3, alignments 1 - 4)." One of the most common btw. The class 2 driver is described as "the low-compliance short-throw high-resonance high-Qt driver that one normally associates with moderately inexpensive drivers."

Interestingly, Keele modeled three pseudo B6 alignments with three different drivers: 15", Fs 40hz, Qts 0.38 (B4), Xmax 4.3 mm, 50W; 12", Fs 22hz, Qts 0.25, Xmax 6.4 mm, 40W; 8", Fs 90hz, Qts 0.7, Xmax 1.8 mm, 15W. Its pretty evident these are not super woofers. Will they produce 120+ db bass? Certainly not, this isn't the point at all by the way, but rather that sixth-order configuration "... allows the designer to "milk" more usable low-frequency output out of this type of driver than any other system configuration." (P. 356)

Keele adds that even though the class 2 driver is handicapped by "high resonance and low displacement capabilities", "Appendix II describes a sixth-order system design using a typical class 2 driver which has usable response down to an octave below the driver's free-air resonance."

His conclusion for the "B6" 15" driver is: "This modification somewhat reduces the maximum acoustic output capabilities of the system in the 35-70 hz range, but greatly increases the maximum output below 35 hz ..."; For the 12" woofer, in QB3 box, F3 39hz, thermally limited > 27hz, but in the "B6" box F3 26hz, thermally limited down to 21hz!; For the 8" driver in C4, F3 55hz, in C6 F3 38hz (from Fig. 7) and "... thermal limit extension down to less than 40hz." (P. 359) These are considerable gains for "old dog" type woofers.

Here I have looked at vented VS vented B6 box, not sealed VS vented B6 (also included by DBK) which I think isn't really fair because of quite different system type, but these comparisons have shown even more dramatic improvements.

This shows that less performing older woofers CAN greatly benefit from step-down mode, contrary to some belief governed only by LF highest maximum db SPL . We'll see later that some super woofers appear to benefit much less from step-down...

More to come.

Richard

RMC

03-01-2018, 10:18 PM

B2) KEELE

The "vent modification assembly" Keele refers to in his paper (P. 356) isn't really a "modification", instead it's a simple vent blocking device, as executed by E-V in the TL series and other boxes. More on this further.

The trick of making two vents and blocking one for step-down, mentioned in a post here, has been around for at least 25 years and the fatherhood of that idea doesn't appear to be Keele's, plus its not in his sixth-order alignment paper. For example, In previous posts in this Thread links were made to E-V's 1993 TL 3512 low frequency enclosure data sheet. On page one, Description section of that data sheet, E-V indicates: "The low-frequency limit of 38hz (3db down) may be extended to 28hz BY COVERING ONE VENT and applying appropriate low-frequency equalization (see Step-Down section)." That system is built with two vents, and a supplied port cover for one as indicated in the spec sheet's step-down section. Because Keele wasn't working for E-V In 1993, being elsewhere between 1976 and 1996 as per his own career path on the home page of his Web site, that idea of having two vents but covering one for step-down mode, seems to originate more from E-V. Ray Newman (RIP), then Chief Loudspeaker Engineer at E-V could be the father of that idea, when reading the acknowledgment at the end of Keele's paper.

More important though, blocking one port MAY not be the "Nirvana" that some think it is, at least at first sight. Initially, for me this raises a big red flag, that members, Keele nor E-V never mentioned in their writings, as far as I know: the possibility of a significant increase in vent air speed or velocity (Mach), with a reduced vent surface area by 50%!, that may well be accompanied by port noise. A non-issue? Why then? Or is it simply ignored/skipped by Keele and E-V? I haven't seen yet any mention or explanation about this.

In the References section of his Sixth-order Vented-box article, Keele did mention as Ref. # 2 and 10, R.H. Small's Vented-Box Loudspeaker Systems, Parts 1 (small-signal analysis) & 3 (synthesis). Keele didn't mention Part 2 (Large-Signal Analysis, vents are part of this one), which is surprising since in Part 3 Small says "The vent design is carried out in accordance with Section 8 of Part 2."(P.334) That section 8 of Part 2 titled "Vent Requirements" (starting P. 329) could be one of the easiest to understand among all Small's stuff. Published 1973, 1-2 years before Keele's paper it's impossible in my view he didn't see it, same applies to E-V I think (i.e. if one reads parts 1 and 3 why not part 2?). With a simple look at Small's Part 2 article summary, right on the first page, one can read:

"The vent area must be made large enough to prevent noise generation or excessive losses; the required area is shown to be quantitatively related to enclosure tuning and to driver displacement volume." (P. 326)

[BTW much later, A. Salvatti, A. Devantier and D.J. Button of Harman have also insisted in the conclusions of their extensive vent study on the importance of largest vent area: "Vast historical data and the results presented in this paper suggest that the largest port area allowable by a given design should be employed to keep the air velocity down if low port compression and low distortion are desired." (Maximizing Performance from Loudspeaker Ports, JAES, Jan./Feb. 2002, P. 43)]. This shows the requirement has not changed and that it's not a trivial detail.

Considering woofer air displacement volume increases with power input, at low level power this may not be a problem, but as the input level increases, so does cone travel and air moving. Then it could become an issue, particularly since we are in deeper bass territory here...

A possible way out of this vent noise I can think of, assuming its a non-issue, is the somewhat reduced LF SPL output compared to normal mode SPL and/or Faux applied higher than normal in some cases, specially when boosting at Fb or close where maximum air passage in the vent occurs... In other words, more of deeper bass output than normal mode, but this at a lower level than normal mode permits a little higher in the spectrum (e.g. 113 db @ 40 hz VS 110 db @ 30 hz; equivalent to half power).

By analogy, if you model a 300 watt driver/box combo in speaker design software with a vent surface area that's smaller than ideal, the program should raise a vent Mach red flag. However, if you reduce in the software the driver's 300 w rating to 150 watts or so (i.e. half power), the red flag often turns to green light! Minimum required vent surface area IS also related to power input, and Fb, Vd. Lower level = less air flow = less noise.

The boost and cut filter may also be part of the explanation when Keele mentions its use to "... return the response back to a roughly flat condition as shown in Fig. 2, curve b." (P.356) It can be seen in that figure 2 response curve, and also on some of the response curves in Fig. 1 and 7, that ROUGHLY flat often entails a VLF response level (boost aspect) that is somewhat lower in the step-down range than what the normal mode range shows. Naturally, things don't get better with power input increases, as shown by the LF maximum acoustic output curves (Fig. 4, 6, 8). The cut aspect of that filter, generating a much steeper slope below passband, would also be a contributor for less air flow and noise in that tentative explanation.

This COULD explain why a single operating vent representing only half the normal mode vent surface area, MAY still manage to take the amount of air passing in the vent without whistling.

More to come.

Richard

RMC

03-02-2018, 05:43 PM

B3) KEELE

Another way to try to make sense of this possible vent noise issue, would be if Keele/ E-V oversized their vent diameters to begin with so that the remaining unblocked vent would still be large enough for free air flow? Though one can get into space trouble with larger vent area also requiring longer duct for same Fb. In any case, neither Keele nor E-V mention or discuss vent dimensions/noise matters (only Fb).

BTW In their B6 2245H boxes Kramer/Timbers indicated (P. 5 & 6) a 5 7/8" dia. vent 12 in. long (8 cu.ft. assisted, Fb 26hz) and a 9" dia. vent (12 cu. ft. assisted and unassisted, only duct length varies: 30 in. and 20 in. respectively, Fb 20hz and 25hz respectively). Now, compare these very long duct lengths (20 in. and specially 30 in.!) with what R.H. Small says about this in his Vented-box... Part II, P. 330, top right, second paragraph. Looks like some bending the rules occured here, from knowledgeable fellows (Kramer/Timbers).

More on the way.

Richard

RMC

03-03-2018, 04:28 PM

B4) KRAMER/TIMBERS LONG VENTS CLARIFICATION

Since someone asked me what R.H. Small wrote about long vents (re post # 77), here is the quote for the benefit of all:

"Also, tubular vents for which the length is much greater than the diameter tend to act as half-wave resonant pipes, and any noise generated at the edge is selectively amplified. In these cases it is better to use a drone cone or passive radiator in place of the vent [2], [23]."

Small's references # 2 and 23 here are from B.N. Locanthi, and Olson, Preston and E.G. May respectively, both from the 1950's. If my memory is correct, both Locanthi and May were former JBL Engineers... If so, then Company memory might have forgotten something. Maybe Kramer/Timbers did test their boxes for the resonant pipe issue raised by Small. But I sure don't recall seeing that in their article I read many times, and where a simple phrase saying "we tested for that and no problems occured" would have buried the issue. Or they might have just ignored the bugger, similar to Keele/E-V on another vent issue? (see post # 76, 3rd paragraph, last lines).

Kramer/Timbers also mentioned in their references, R.H. Small, Vented-box..., Part III:Synthesis, not Part II where vent requirements are outlined however. But as I mentioned before, Small did write in Part III "The vent design is carried out in accordance with Section 8 of Part 2."(P.334) Doesn't that sound familiar? That alone would make me rush to go check Part II, as I did (see post # 76, 4th paragraph). Small being in 1973, long before Kramer/Timbers in 1983, they presumably saw that.

Some aspects of vent parameters/performance appear to be left on the sidelines by some experts, even though these are far from being negligible aspects. I suppose they wanted to avoid opening a "can of worms" type of discussion? Or the associated complicated explanations? My only point here though is simply that product end users may not be informed about all the relevant stuff there is to know... So, when I see it I raise it.

Some interesting vent blocking stuff in the next post, coming soon.

Richard

RMC

03-03-2018, 09:51 PM

C1) VENT BLOCKING SUGGESTIONS

"The vent area may be either all-in-one or split into two or more separate vents, as long as the total vent area remains the same." (E-V, DL18W, data sheet, 1984, P.2)

Blocking one of two vents or half of a single vent is basically the same issue (i.e. a 50% vent surface reduction). MAYBE a one remaining complete vent could have better air circulation than a single vent partially blocked, both having the same surface area? On the other hand, experts have mentioned many times (e.g. JBL Enclosure guide) that vent shape (round, rectangular, square) doesn't matter. I've also seen some triangular or so shaped vents, though inside angles were rounded which makes sense, near the bottom front baffle's corners on commercially available speakers.

Multiple vents take more space than a single one of same area, in my view, simply because of repeated vent tube thickness and spacing required between each one. In a large box that is not really a problem, as multiple smaller diameter vents can be placed and spaced almost anywhere on the baffle. However, as box size decreases, which is the main appeal for step-down use (smaller box with deeper bass), then it may become an issue. e.g. For space reasons most of my boxes are rather small (< 3 cu.ft.Vb), so a single vent makes more efficient use of space available on the front baffle, specially for 2-3 way systems, though I know the vent could be placed on the back, top or side panel (which I never do because of extensive panel bracing).

Surprisingly, E-V had no suggestion or option for Home Speaker Builders, in their Pro Sound Facts no. 7 "Step-Down Bulletin", to block a vent or part of it, contrary to their commercially available TL series and others sold with a supplied port cover in numerous cases. I imagine they figured people would build the normal version or the step-down version (both in the Bulletin for each box size). Why not have it both ways, i.e. same box that can do normal and step-down modes like the TL series? [BTW in the Bulletin I counted 13 boxes with single vent (2 in normal mode and 11 in step-down mode), others having mostly two, some three or four vents]. My own vent blocking suggestions follow for speaker builders, since none are given by E-V (you either built normal or step-down version). Members may well have quite a few more of their own to add...

For double round vent home made systems, blocking one vent is relatively easy even in the absence of a commercially available port blocker. For example, thefoamfactory.com sells closed cell cylinder shape pieces of foam in 1.5, 2, 2.5, 3, 4, 5 and 6 inch diameter which should tightly fit in most common port sizes. Failing that, you can tightly pack or stuff a vent with similar type of removable closed cell foam. Open cell foam is less desirable though "...due to the high air-flow its structure allows". Remember, here you're not looking for a working resistive vent (like many in the old days), but rather for a blocked vent with no air going through. Doing it this way you can easily revert back to normal mode if required (e.g. normal mode if the highest possible low frequency SPL is needed for a specific application, as E-V said in an earlier post).

Rectangular or square vents are also relatively easy to block completely (1 of 2) or partially for single vent, in a way you can also revert back if need be as above. Cut an appropriate dimension wood block that will tightly fit inside the vent (all or half the internal volume of it, as the case may be) and use removable caulking to seal air tight around the wood block's perimeter. Example of such product: Mulco's, Zip, Seal' N Peel, removable clear sealant. In the case of half vent blocking, use sandpaper on the wood block's side exposed to vent air flow for smoothness.

Single round vent partial blocking for step-down can be more challenging. Making a half foam cylinder from one of The Foam Factory above MAY not be ideal (though removable sealant may help to hold it and seal it). First, since it might not fit and hold tight in place, will it stay there during loud speaker use without glueing (for later removal if need be)? Second, I'm not sure the foam's soft material would have as smooth surface as required exposed to air flow, once cut lengthwise with a sharp blade for a ducted port. Cutting this way tends to be more messy than precise (smooth & straight) which may impede vent air flow.

You'll have to make a half-moon shape out of something fitting tightly in the vent for the full length of it, preferably smooth & straight on exposed surface, like a rigid plastic or wood piece, and fasten it temporarily at each end of the vent, for usage and later removal as required. Removable sealant can be of help here too, not only to hold the half vent blocker in place, but at the same time to seal air tight on the device's rounded perimeter at each vent end. In a pinch, tape could also be used to do the same as sealant, even for testing purposes like checking the new Fb.

Still more to come.

Richard

EDIT: RE E-V "you either built the normal or step-down version" and "why not have it both ways in the same box" above. Naturally, when building the normal mode version its easier to convert the box to step-down mode by simply blocking half of the vent surface area. However, when building the step-down mode version its a lot more (vent) work to convert it to normal mode because the vent dimension(s) are not the same for the two versions as per E-V's Bulletin (diameter and/or length). Lower tuning (step-down) usually implies smaller diameter and/or increased length vent, whereas higher tuning (normal mode) usually implies larger diameter and/or shorter length vent. So it makes more sense (less work) to start with and build a normal version and step-down it as required, than the other way around.

Richard

RMC

03-08-2018, 12:28 PM

D1) JBL

The JBL modelings of B6 or so alignments were in very limited number compared to E-V, maybe because many (not all) JBL's often have higher Xmax number which makes Step-Down mode less necessary or appealing for deeper bass achievement alone. However, still quite interesting for smaller box size, with deep bass. Kramer/Timbers understood the size reduction opportunity quite well: "For this project, we chose the latter system [RMC: 8 cu.ft. assisted box] because of its more moderate size. The 26-hz cutoff was deemed low enough..." (...) "... Why equalize? In order to keep the efficiency up and the box size down,..." (P. 4 of their 1983 article).

Their priority towards smaller box size is justified by a good reason. A similar performing (F3) unassisted system has a 12 cu.ft. net box in their article, and such a large size isn't an easy sell to the public. Even more so when considering that about 15 cu.ft. gross volume would be needed normally to get that net volume when everything is accounted (driver, bracing, vent, losses). Naturally, this was also the opportunity for JBL to present and launch their B460 and B380 subwoofers/BX 63.

Kramer/Timbers have shown for the 2245H in 8 cu.ft. assisted box VS same driver in 12 cu.ft. unassisted box a noteworthy 4 cu.ft. size reduction and "The 12-cubic-foot unassisted design gives essentially the same response curve as our 8-cubic-foot project box... Again, the trade-off is enclosure volume versus amplifier power." (P. 6) This means the F3 of the unassisted 12 cu.ft. box would also be at 26hz or so (F3 mentioned for 8 cu.ft. box).

Since the F3 of the assisted 12 cu.ft. box is said to be "about 21hz", that leads to a small 5 hz F3 difference between 12 cu.ft. assisted VS unassisted (same box size and driver). Is that minor gain here really worth the trouble/money of going the assisted way? Which they considered here overkill for most program material.

Moreover, in post # 29 here JBL's 2269H was modeled in a unassisted vented box, QL 5.4, Vb 8.9 cu.ft., Fb 26 hz, F3 32.47 hz. Then same box/driver with 26 hz EQ boost/cut filter assistance, filter Q 1.5 (not the usual Q 2), and the new F3 stands at 24.63 hz. The difference between the two F3 (pre and post EQ) is 7.84 hz. Again not a major VLF assisted gain for a super driver, compared to what some moderate ones benefited in LF.

The above JBL examples "unbolt" the myth that VLF capable drivers would be better candidates for deeper bass with assisted alignments. They probably have more to gain from assistance's usual box size reduction capability, than on F3. These two woofers can achieve very deep bass on their own, with no EQ, but at the cost of very large boxes. Hence the appeal of assisted alignment for a smaller box size with comparable F3.

Also, contrary to another myth, there ARE a number of older JBL or other drivers with limited cone travel capabilities that could benefit more of deeper bass this time, than box size reduction, from step-down. That is patently shown by Keele in his paper, even when comparing vented QB3 VS vented pseudo B6 (not only sealed VS vented box). See post # 75.

BTW In their article Kramer/Timbers did build and listen to a sealed box, both sealed and vented equalized for similar response and using 2245H, where they indicated "... the dynamic performance of the vented system was judged to be significantly better." (P. 3)

More will follow.

Richard

Ian Mackenzie

03-09-2018, 01:38 PM

Hi Richard,

FYl

If you refer to DB Keeles formulae the Jbl 2269H will have an assisted step down Fb of 23.3 hertz
The box volume allowing for 20% box losses is 150 litres internal volume.

I quick online bass reflex calculator while l am walking the dog suggests an unassisted tuning of 191 litres, Fb is 30 hertz nand F3 is 31 hertz (W.J.J Hoge)
http://www.mh-audio.nl/reflexboxcalculator.asp

Jbl 2269H
Fs 28 hertz
Qt 0.36
Vas 237 litres

I don’t have time to re think your last post.

Okay l have posted the Bassbox simulation to illustrate what the Jbl 2269 does under 3 box scenarios

People can make their own mind up on preferences.

The Magenta curve is maximally flat alignment 137 L 4.8 cuft3
The Cyan curve tuned to 30 hertz 197L 6.9 ft3
The Yellow curve is the Keele assisted alignment f3 about 23.7 hertz , Fpk 25 hertz 150L 5.3 cuft3

A few points

Obviously the enclosure for the Keele alignment only a bit larger than the maximally flat alignment.
The larger 197 L unassisted alignment offers more extension with the penalty of box size.

The maximally flat F3 is 35.5 hertz versus 23.7 hertz on the assisted Keele alignment. That’s huge but under what conditions will that be subjectively important?

Comparing the Keele assisted alignment maximum displacement limited output to the unassisted alignments it drops 9 dB in output @29.5 hertz, the Fb of the maximally. That’s huge. The trade of is extension to 23 hertz.

The Keele assisted alignment is a compromise on the maximum displacement limited output for bass extension.

What the subjective result is is a matter of setting up an enclosure and auditioning these scenarios.

Ian Mackenzie

03-09-2018, 09:40 PM

“The above JBL examples "unbolt" the myth that VLF capable drivers would be better candidates for deeper bass with assisted alignments. They probably have more to gain from assistance's usual box size reduction capability, than on F3. These two woofers can achieve very deep bass on their own, with no EQ, but at the cost of very large boxes. Hence the appeal of assisted alignment for a smaller box size with comparable F3.

Also, contrary to another myth, there ARE a number of older JBL or other drivers with limited cone travel capabilities that could benefit more of deeper bass this time, than box size reduction, from step-down. That is patently shown by Keele in his paper, even when comparing vented QB3 VS vented pseudo B6 (not only sealed VS vented box). See post # 75.”

Based on my simulation and unless l am having a “seniors moment “ your first paragraph is a generalisation based on less than appropriate evidence.

My base line examples clearly illustrate the capabilities of an appropriate hi powered hi Xmax driver under 3 operating standard operating conditions.

The strengths and caveats are clear.
The user can make informed enclosure/ alignment decisions to suit their specific application.

My suggestion is set up an Excel spreed sheet and do a comparison of a dozen Jbl woofers and compare them with 3 alignments as l have done. You can then talk about trends.

You might then be in a position to make a recommendation.

RMC

03-10-2018, 10:21 PM

D2) "SUPER WOOFERS", AND OTHERS

As I mentioned in an earlier post RE E-V's huge 30W woofer (and comparison with JBL's 2245H) there isn't a whole lot to gain in terms of assisted deeper bass, when dealing with already low F3 numbers these drivers can achieve by themselves. That amount of additional benefit is less evident or important for super drivers.

In recent posts here I showed the following lower F3 gains from assisted alignment VS unassisted for the JBL 2245H, 2269H and E-V 30W, with same box size, to be 5hz, 7.84hz and 8.5hz respectively. This is less than what "ordinary" woofers have shown, which is usually a good 10 hz. Keele's own pseudo B6 modelings of three quite "ordinary" woofers showed 12hz, 13hz and 17hz lower F3 improvements compared to standard vented box (these were respectively 15", 12" and 8" woofers).

Even though the 2235H isn't considered a super woofer by today's standards, I'm including it here for comparison purposes, considering JBL's previous mentions about it, such as: "... drivers for demanding professional applications, in which very high sound pressure levels at very low frequencies are a requirement." Reference is also made to 25-50hz octave at levels in excess of 110 db (Brochure LFS/5-83).

In post # 11, a 2235H modeling was done: Vb 4.5 cu.ft, Fb 26hz, 150W, for both assisted and unassisted versions. "Response" with EQ flatter and 6 db higher at 30hz than with no EQ, plus around 24hz still about 4-5 db above the no EQ level. The "F3" is at 40hz (no EQ) compared to "F3" of about 26hz with EQ ("response" and "F3" since not at usual 1W, but at 150W input). The 150W output level represents a healthy 116 db @ 30hz and 113 db around 26hz which beats the above 110 db. In terms of lower F3 improvement, the assisted box shows here a sizable "F3" gain of 14hz. Another older driver (35 years old) showing a fairly large VLF extension gain from assisted alignment.

For super drivers, I see more practical potential on box size reduction, with similar F3, than on chasing the minor or ultimate lower F3 using assisted LF. These can pump huge amounts of VLF, if required, in the case of JBL's due to their extra long cone travel capability, and in the case of E-V's due to its enormous cone size. As indicated by E-V in many documents, the "penalty" for not using step-down is much larger box size required: "To achieve a similar response extension without equalization would require an enclosure at least twice the size, ..." (E-V, TL 3512, data sheet, P.3). Links to this one were made in a previous post.

With regards to drivers with more limited Xmax capabilities, the major gain from step-down use is deeper low frequencies at a higher output level, as shown in Keele's article examples.

As for the appropriate woofer size myth, Keele's modeling of a CTS 12" driver (and 8" woofer) speaks by itself: for the 12" woofer, in QB3 box, F3 39hz, thermally limited > 27hz, but in the "B6" box F3 26hz, thermally limited down to 21hz! Plus, I have another such example from a reputable source which we'll see in an up-coming post.

Richard

Ian Mackenzie

03-11-2018, 06:11 AM

Hi Richard

I can see what you trying to say.

However, I think the apples for apples comparison are a bit off.

Firstly, when referring to an unassisted alignment it needs to be understood which alignment, QB3, SBB, maximally flat or extended shelf alignment is being discussed for comparison purposes.

Without making a selecting a standard un assisted alignment any comparison for discussion purposes is too random when comparing to B6 alignments.

My suggesting is use the Hoge alignment.

http://www.mh-audio.nl/reflexboxcalculator.asp

I have not looked at it too deeply but attempting to gain a lower f3 in the case of an un assisted alignment for the JBL 2269 beyond the 6.9 cu ft3 Hoge alignment results in a sagging response below 100 hertz by about 2 db or so and then a corner F3 of around 25 hertz. ie 9 cu ft3 tuned to 25 hertz or below down to 21 hertz as seen elsewhere.

In an application as a sub crossed over any say 65 hertz you could live with that but if it was a 2 way system the woofer response would warrant a LF shelf EQ lift below 100 hertz to balance the overall system.

I am not sure why you are singling out the 2269 in such a large box when in 197 Litres (6.9 cu ft3) it does an admirable job with an f3 of around 30 hertz without being too big and the response below 100 hertz is maintained at reference sensitivity.

In my comparison the actual B6 is 150 litres and it gets down to 23 hertz. The moment of truth is the caveat of the significantly reduced LF output at 30 hertz.

I am not sure what you are referring to as a super woofer or in your mind what its meant be constitute?

As far as the B6 F3 is concerned its simply the ratio of F3/Qts.

The lower the Fs and higher the Qt the lower the F3 will be where F3= Fs/Qt x 0.3

The B6 Vb is governed by the formula Vb = (Qt )2 x 4.1 x Vas. In this formula the lower the Qt and the lower the Vas will yield a smaller Vb.

In practise it will often be a lower Vas and higher Qt as in the case of the JBL 2269 or a lower Qt and a large Vas like the JBL 2245. (237 L versus 821 L respectively)

In the case of the JBL 2269 you end up with a lower F3 and a smaller enclosure while the JBL 2245 you end up with a larger enclosure for B6 purposes than un assisted QB3 alignments.

RMC

03-11-2018, 04:48 PM

"Vented Box Calculator

according to W.J.J. Hoge

This set-up provides the highest precision and a flat frequency response"

A word of caution and explanations regarding the often mentioned Mh-Audio box calculator, for the benefit of all readers. The Mh-Audio calculator is using an APPROXIMATE vented box design procedure (not the exact real thing, Mh Audio doesn't say that), as I mentioned in a post in another thread sometime ago.

I know since I used the method a number of times many years ago before computer design software became widely available to the public. It was the next best thing to Thiele and Small writings, also not widely available to the public in the old days, unless one subscribed to JAES from the early 70's and on. I've had this method since It was published by John Hoge in "Confessions of a Loudspeaker Engineer", Audio, August, 1978, P. 47. As a Loudspeaker Egineer, Hoge described here ONE of the methods he used (the easiest Re public use) for vented box design, along with some speaker related physics. Hoge himself indicates on page 50 "...developed by Keele and represents an approximation of the charts given by Small for systems with an enclosure loss factor of QL = 7."

Contrary to some belief, Keele never published that, not even on his Web site, but he did circulate his method in private communications to experts in the audio industry (John Hoge, John Eargle, David B. Weems, Ray Alden, etc. have indicated getting this procedure through private communication from Keele). For my part, I got after Hoge's article, an "improved copy" of Keele's original procedure "Vented Box Design Using Pocket Calculator, February 1976", made by Bolt, Beranek and Newman, the famous Acoustical Consultants firm, and that one is dated June 1, 1977.

My edition of this is an 8 page compilation of Thiele, Small and Keele design and measurements equations/formulas for vented box. After a couple of pages of parameters definitions and measurements techniques/calculations, it says: "Now use Vented Box Design and Vent Design calculations by D. Keele." and Keele's approximate method follows on 3 pages. Pretty loaded but concise document, just enough text but lots of math to do with a pocket calculator...

So, Keele's method is also outlined here with corrections/improvements from the folks at Bolt, Beranek and Newman (BBN). Its a typed document on 8 1/2" X 11" but a number of alternative equations/formulas are hand-written next to some of the original ones. Its in this document I was able to confirm a typo existed in Hoge's equation # 19 (vent length formula) where the exponent is negative, instead of being positive as in the BBN version. The vent Lv numbers calculated finally made sense...

John Eargle (JBL): "The approximate design equations, as given by Keele, are shortcuts to estimating certain aspects of system response." He adds they have an accuracy of about + or - 10% (1 db). (Handbook of Sound System Design, ELAR, 1989, P. 104).

However, Robert Bullock, Mathematician and Professor of Applied Mathematics at University, has shown things can get worst than that: "Formulas also exist for Small alignments; for example, Hoge provides formulas for QL = 7. These formulas can be off by as much as 25 percent for some alignments. (...) If you like to play with formulas, I have included some of my own construction for QL = 5, 7, 10 in table IV. I make no claims about their accuracy except to say that they should be as accurate as those Hoge used." (Bullock on Boxes, 1991, P. 8).

Bullock further mentions about his own formulas in Table IV (P. 6 ) " The value of H [RMC: re Fb] is usually within 2%, the value of F3/Fs [RMC: re F3] within 6%, and the value of Alpha [RMC: re Vb) between - 17% and + 25%." The latter is the major bugger I see here with Alpha's tolerance (Re: Vb), considering Hoge indicates: "Remember, cabinet volume, Vb, is probably the single most important specification of a loudspeaker system." (P.47)

So, "Highest precision" as claimed by Mh-Audio??? No, not at all in my view, as one can see from both Eargle and specially Bullock, even more so when compared to today's numerous speaker design software programs available. It seems Mh-Audio took the easiest way, period. "OK" for some "trial run" re woofer potential , quick test or to get some idea, but not enough accuracy for the final product (box) by today's standards.

There's nothing wrong with using an approximate box design method, I did LONG ago, but one has to know what he's using, know its shortcomings (e.g. for QL 7 only; accuracy tolerance) and be willing to accept these facts. It's also ok if one has no access to anything better. Unfortunately, Mh-Audio isn't straightforward about all this.

BTW another known approximate design method exists: Gary Margolis (JBL) and R.H. Small, Personal Calculator Programs for Approximate Vented-box and Closed-box Loudspeaker System Design, JAES, Vol. 29, 1981, P. 421-441. Some of their equations/formulas were reproduced in article(s) of Speaker Builder Magazine.

Richard

Ian Mackenzie

03-12-2018, 06:47 AM

ivica

03-12-2018, 10:06 AM

The point is the benefit of looking at several different types of alignments to compare enables the user to make the most informed choice to suit a particular application with a particular driver.

I am not aware of any evidence in your posts that supports the above.

I have numerous program and that online calculator was convenient at the time

The actual process can be as complex or as simple as a user requires and that’s not your call.

Hi Ian,

I have to agree with You.
Here, from the theoretical point of view, it can be written more then a book, but we have to be aware that in usual home listening surroundings, bass response in our rooms is so 'un -predictable' and its variations is much, much more then +/- 3dB, so EQ, here talking about would be fare from the calculated prediction.
Even putting bass driver in the middle of the wall would not help enough , if very low frequency is of interest, as driver(s) mutual coupling (if stereo is applied) or drivers 'image' (as a reflection from the large surfaces such as walls, floor, ceiling ).
I think forum members with the good experience about the topic would give us some good experience with the bass response in standard home listening conditions, but that would be CONFIRMED with some measurements data (not only such as:..."move 1m from the walls, etc.."

regards
ivica

Robh3606

03-12-2018, 07:56 PM

Here, from the theoretical point of view, it can be written more then a book, but we have to be aware that in usual home listening surroundings, bass response in our rooms is so 'un -predictable' and its variations is much, much more then +/- 3dB, so EQ, here talking about would be fare from the calculated prediction.

Hello Ivica

Not sure I can agree with you on this. You most certainly get the extended bass response as promised in the simulations. The overall response will be tailored by room placement just like any other system but make no mistake you would have to be deaf not to hear it the difference. Room response be damned you cannot miss the extra half octave.

Rob:)

ivica

03-12-2018, 10:48 PM

Hello Ivica

Not sure I can agree with you on this. You most certainly get the extended bass response as promised in the simulations. The overall response will be tailored by room placement just like any other system but make no mistake you would have to be deaf not to hear it the difference. Room response be damned you cannot miss the extra half octave.

Rob:)
Hi Rob,

I want to say that here it is talking about several dB of improvement , but in the room, it can be get the variation over 10dB from the 'open space' prediction (2pi), especially if we have two (stereo) drivers working in LF frequency domain. But I agree that any speaker response would be tailored by room placement.

regards
ivica

Ian Mackenzie

03-13-2018, 05:02 AM

Room modes are a can of worms.

Richard has not to the best of my knowledge mentioned room modes despite sifting through numerous papers.

Back to the fun stuff has anyone heard a Sunfire sub. You know the 2700 Watt 1 ft square cube?

Robh3606

03-13-2018, 05:49 AM

Back to the fun stuff has anyone heard a Sunfire sub. You know the 2700 Watt 1 ft square cube?

Hello Ian

I have seen them often enough but never heard one in use. So why do you ask as it pertains to this thread?? Does it use a similar alignment?? Always wondered what they sounded like. I have always had a preference for large surface area with minimal movement as compared to small surface area with extreme movement. Not sure why because if the displacement of air is the same it shouldn't mater. The larger cones just seem to sound better??

Rob:)

Ian Mackenzie

03-13-2018, 12:25 PM

I bought it up because of the recent discussion on placement.

If this thread was a newspaper on the coverage of who will get in next election it would be one side A4 sheet.

It’s a look through a key hole.

Sometimes raising product outside of the immediate discussion opens up the mind.

The beauty of the Sunfire is it can be placed anywhere without hinderance or in multiples across a room or typically in corners.

Corner placement of 9 cu ft3 or other options is going to be restricted by sheer size. Location and spread of subs is critical to obtaining a worthwhile result.

Yes it’s time to enter the real world. Context is a useful thing when applying theories to reality.

If you google bass, particularly in small rooms it’s well documented as one of the most difficult things to get right if at all. In some rooms their are non recoverable issues that impact deep bass.

One way around this is to place the sub right next to the listening position. It’s called global.

The other point is power. The Sunfire is a good example of why you need a line to the local power station of you have a relatively small driver. I don’t believe the physics in layman’s terms has been spelt out in a way that makes the notion of the step down tuning real. It hasn’t been qualified.

So before you buy longer pvc ports do some evaluation of your room then look at your woofers.

Is attempting deeper louder bass realistic?

Look up REW to find out what is and isn’t fixable with EQ of your bass.

Will my existing box cut the mustard?
Will step down of my LE8T give me low bass? How loud can l play it?
What can l expect out of my 4311 in step down mode? What are the pros and cons of attempting the modification?

The thread has looked at the step down tuning in almost isolation of the realities of reproducing deep bass other than some notable examples of Jbl subs. No factual attempt has been taken to screen or quality existing system or drivers for suitability.

Then there is the application of home theatre or music?
I would suggest a lot of people today have blended systems. Those with dedicated HT would almost certainly have existing subs.

The other obvious but overlooked point in these arm chair style forum discussions is that today’s recordings are nothing like the 70’s when the step down paper was written. Back then it was vinyl or cassette.

CDs, DVD audio and SACD don’t take take prisoners in terms of what bass placed in a recording. The demands on a woofer are much higher. Amps are much more powerful today and will pole a VC.

I don’t think a real scenario exists where you want play a recording with deep bass quietly.
Anyone selling that is absolutely full of shit.

Therefore one would hope common sense applies and the user out sources the desire for deeper louder bass to a dedicated sub rather than squeeze a quart out of a pint bottle. It ain’t gonna work and many Jbl recones are now NLA.

Of course some idiot go and do it.

In summary the usefulness of the content in this thread needs to be well
qualified. It requires well thought out discussion on the introduction of step down to an existing loudspeaker system and a process for evaluating suitable drivers for a new system or sub.

RMC

03-15-2018, 11:14 AM

Thanks for coming back again and again, its the best way of expressing that you really like it.

Making the usual noise, distortion and beating around the bush that doesn't cut it, is quite similar to the guy repeatedly saying this store is real crap but keeps shopping there all the time... even though there are numerous other stores available (like threads). Looks pretty much like "if you can't beat them join them" to me.

The most important signal is certainly that you keep voting for it everytime you click on the thread's link... to have more than a peek. So as it is the Thread DOES capture a lot of interest otherwise you wouldn't be here, Right? Getting close to 4,000 views isn't bad for an "irrelevant" thread don't you think? Unless they're all your clicks.

Even though you have all leisure to compete with this thread, for the benefit of all readers, by setting-up your own thread on LE8T/4311 or other step-down process, with your own material and info, but as usual refrain from it. Similar to "bleachers managers" at the baseball game.That says a lot. Of course you prefer to come back here for two reasons we probably know already.

After all is said and done, the recurring views only confirm there's a lot more here than you like to pretend. Otherwise, others sure would not hang around an "uninteresting" thread on this site. We're all convinced it won't be long before you show-up again as there is other stuff to post, and you certainly can't avoid looking so you don't miss a thing or two that you'll learn, without admitting to have. We understand.

Thanks again for clicking, and voting for it, one more time, the best flattering expression! We're glad you enjoy this like others do by viewing regularly. Otherwise you'd stay away from it, right?

RMC

03-15-2018, 08:44 PM

E1) CONE EXCURSION

E-V, JBL (in post # 26 data sheets ) and Kramer/Timbers' article did not provide in their documents cone excursion graphs/curves for the modelings they did. But we can refer to some excursion data provided in some posts here. One must remember there are TWO bumps on a cone travel graph with these B6 or so alignments, one on each side of tuning frequency, whereas the usual vented-box design has one bump above Fb and a continuing excursion increase level below Fb (e.g. post # 11).

Its interesting to note for these high level curves there is LESS cone travel reduction at Fb with assisted alignment VS conventional unassisted alignment. This is considered to be the result of applying a 6 db boost at Fb or so (subject to further explanation below), which is equivalent to supplying four times the power at that point. However, this lesser cone travel reduction by the vent at that point is somewhat compensated elsewhere with MORE cone travel reduction, below the assisted tuning frequency VS unassisted design. That reduction is the result of the subpassband 12db/oct. high-pass filter included with the 6 db filter boost (i.e. boost/cut filter).

The excursion bump above the new Fb (in the region of original tuning) may well reach driver excursion limit first because the driver's maximum acoustical output capability is usually reduced by a few db in the region of original box tuning, as a result of lower than normal box tuning. Consequently, more cone excursion there. On the other hand, the excursion bump below the new Fb, a result of bass EQ applied, has a slower rise than with usual vented box, thanks to the high-pass section of the bass EQ filter.

The older 15" 2235H (Xmax 8.4 mm) in post # 11 illustrates at the 150W power rating with assisted alignment the driver isn't out of bounds, excursion being a bit less than 8 mm on the right cone travel bump, and a bit more than 7 mm on the left excursion bump. Not a lot of loose left, but it doesn't have its back to the wall yet. That slower rise on left bump permits here to add, with an equalizer or DSP, maybe about 1-1.5 db or so of bass equalization around the boosting filter's frequency (Faux), then the driver is about done with Xmax on both bumps at the same time...

Vance Dickason also produced a computer simulation, in his Loudspeaker Design Cookbook 5th edition, of a Class I sixth-order alignment similar to others in this thread, "... to show the dynamic consequences..." of such. He used a 12" woofer (Qts 0.30) in a QB3 aligned vented-box, that he tuned at 24.8 hz, used an active filter frequency of 27.14 hz with a Q 1.77, giving a bass lift of 5.33 db.

So Dickason's boost was applied 2.34 hz above Fb, similar to Keele's and many of E-V's own boxes. Comparing his F3 numbers with/without filter shows the expected 10 hz F3 gain from assisted alignment (and the predicted half-octave extension). With regards to cone travel he writes: "Excursion only 5.8 mm maximum for the speaker/filter combination, plus the typical continuing increase in excursion rate below Fb has been attenuated to a low level. Given the 6 mm Xmax of the driver, the Class I system should provide good high SPL performance." (P. 63).

Also interesting from this simulation, are its cone excursion curves (btw similar shapes or so at higher level to 2235H's in post # 11). At the same low input power level the pre/post bass EQ excursion curves match more closely at Fb. But as the level increases they deviate more from each other at Fb (and elsewhere). Since the boosting filter is also present on the low level post EQ curve, and there's a relatively good match of curves at this level at Fb, then why less at higher level? As if the vent's cone travel reduction effect at Fb (and others) couldn't keep up with more input level.

E.g. On "forum.speakerplans.com/assisted-alignment-b6-loading_topic87595.html" one fellow that went the B6 way did mention "... and made port noise a big problem." No box, driver, port or power info being given its hard to even try to name the culprit with any reasonable accuracy.

It seems the bass EQ filter's sole presence/action, which is independent of power level, doesn't explain everything at higher level. Some Port compression also? There's a coincidence: as power input increases the shape of the post EQ excursion curve changes, and as power rises so does port compression according to Salvatti, Devantier and Button's Port Performance article I mentioned re port size in a previous post. They say:

"As the SPL of a port is increased, there is no escaping some degree of port compression." (P. 32) "Several complications occur in vented designs as the output is increased beyond the point where the air in the port is able to respond in a linear fashion." (P. 19). Examples given: extraneous noises made in the port, acoustic compression and distortion. Some food for thought regarding the above-mentioned issue.

More coming with other drivers.

Richard

RMC

03-18-2018, 11:36 AM

A parenthesis regarding speaker/subwoofer placement mentioned in some previous posts.

Floyd E. Toole is THE person to go to for this: from The Science of Audio series of Lectures, "Loudspeakers and Rooms for Multichannel Audio Reproduction, Part 3 - Getting the Bass Right", from Harman's V.P. of Acoustical Engineering! He's been with JBL for many years, is a world- renowned expert on speaker acoustics and knows more about this than almost anybody else. Relatively easy to read, follow and understand, the form is similar to that of a presentation with boxes/illustrations on the left, and short explanations on the right hand side of the page. Google this as its on the Web for free and worth it! If you can't find it let me know I'll post it.

For those wanting a more extended view/explanation on the subject, from two other Harman Engineers : Todd Welti and Allan Devantier, "Low Frequency Optimization Using Multiple Subwoofers", JAES, May 2006, p. 347. Available free on Harman's Web site in the technical papers section where I took it, if I'm not mistaking. Naturally they do discuss some single sub issues also. Even though its from the JAES, there is still a good part of it that is accessible to all.

Like Floyd E. Toole, in addition to being an Electrical Engineer Todd Welti is also an acoustician. ALL these fellows here are practicing JBL Engineers, not theorists hidden in some University department. They know what they're about in real life. There are numerous others available on the Web, however the above two papers from well-respected sources should put you in business...

My next post is about 75% completed, so it should be here in a short while. Regards,

Richard

RMC

03-21-2018, 09:14 PM

1) At the end of post # 94, regarding port compression at the point where its unable to respond in a linear fashion.", some readers may wonder what it really means: "... operating in a nonlinear fashion, which is to say that they are unable to move sufficient quantities of air at the velocity required." Vance Dickason, Loudspeaker Cookbook, 5th Ed., p. 52.

2) For the 15" 2235H modeling done in post # 11 (Vb 4.5 cu.ft., Fb 26hz), that I referred to in post # 94, the vent info (diameter/type) used was not mentioned. However, from the Kramer/Timbers article (P.7), where they modeled the equivalent box, we can infer that a round 4" or so vent was used in post # 11 modeling, since these two JBL guys stated "The port area should be 13.5 sq.in.", which corresponds to Dv 4 1/8" (13.36 sq,in.), plus their box picture shows a round vent. This data justifies adding there might be more port compression negative effect included on the excursion curves in post # 11, when considering Dickason, in the same Cookbook, mentions 4" diameter ports are "usable but minimum for 12" and 15" woofers (p.53). More on this issue further, with other drivers.

3) The recone kit's uncertain availability raised for the 2235H may not apply for the 2245H. For example, assuming Ken is still carrying the torch, then quality reproduction recone kits should still be available for the 2245H based on his Web page (uplandloudspeaker.com), selling them through E-Bay. So the availability of such would not be a reason to "discard" the 2245 driver, as was more or less implied for the 2235H (it was included in my post # 83 for comparison purposes, where it showed good results in step-down mode).

Cone excursion matters for other woofers, plus other stuff, will follow in the next post coming soon.

Richard

RMC

03-24-2018, 07:17 PM

E2) CONE EXCURSION

No excursion data was given by E-V for the huge 30W driver, their only mention in the data sheet being that "Even at full power input, cone motion is within the linear range." Nice but not enough for a simulation.

The 18" 2245H (Xmax 9.65 mm, Pe 300W), "King of bass" for a long time, did have a limitation in one of the simulations done by JBL (third one below). The db numbers below are rounded for clarity.

In the 8 cu.ft. assisted box, Fb 26hz, the 2245 remains thermally limited (300W) down to 20hz, relative response of - 14 db and max output of 108 db (from Kramer/Timbers P.3). From JBL's data sheets in post # 26, same woofer in larger 12 cu.ft. unassisted box, Fb 25hz, the driver stays thermally limited until 22.5 hz, relative response being - 8 db and max output 114 db, plus at 20hz (displacement limited) response is - 11 db and max output is 109 db. Comparing both boxes, for comparable LF performance (20hz/-14db/108db VS 20hz/-11 db/109 db) you can get 4 cu.ft. smaller box with assisted alignment I mentioned previously. The steeper roll off of the assisted box, with a high-pass filter, usually explains the response difference of the two. If we compare both at 22.5 hz (lowest point where larger box is thermally limited), 8 cu.ft. response - 11 db, max output 111 db; 12 cu.ft. - 8 db, 114 db, so the larger box has a 3 db edge on response and output at that frequency.

Note the 8 cu.ft. Fb 26hz assisted box does not show (in JBL's modeling computer printout) any sign of reduced max output capability nor excursion issue a little higher in the bass range, since tuning is higher and box smaller (see below though).

Also note the 2245H max output of 122 db higher in the spectrum (150hz) is the same as for E-V's 30" woofer at 122 db (100+ hz)(post # 71). The former requires at least double the power input for this level, while the latter requires a huge box size for very deep bass...

In the third simulation done by JBL (12 cu.ft. assisted, Fb 20hz) the 2245H had a little more difficulty keeping up with power input even with its large cone travel rating (post # 26, last document). Here the driver remains thermally limited down to 40 hz (response -3 db, max output 119 db), then gets displacement limited from 37.5 to 27.5 hz, which would be represented by the right-hand excursion bump on a B6 alignment cone travel graph, showing it reached Xmax prematurely in that range. After, it resumes being thermally limited from 25 hz down to 18 hz (resp. -11 db, spl 111 db).

At the worst case point where it ran out of excursion (centered at 32.5 hz, resp. -4 db, max out. 117 db) it could take 243W instead of 300W, 57W less or a 19% input power reduction. In terms of relative db output loss caused by unsufficient excursion, this represents almost 1 db (see printout). (-1db is equivalent to 20% power reduction based on J. Eargle's power ratios table in Handbook of Sound System Design, p.9).

So this "super woofer", in that particular setup, suffered a little, but less than most, from the reduced max output capability in the region ABOVE Fb (region of original box tuning as E-V calls it). That reduced capability generated a little excess cone excursion here. 20hz tuning in a very large box with LF filter boost is a big order for about any driver. Graphically, the right excursion bump would be higher than the VLF left one at practical frequencies (not 15hz). (You'll see later another woofer didn't have its back to the wall, but its a different situation).

For the same 12 cu.ft. box size, comparing the assisted and unassisted 2245 versions, in that order, at the lowest high-spl frequency from each (thermal limit), there's a 4.5 hz difference (18 VS 22.5 hz). Not enough to be bragging about the LF gain here from B6 alignment. Moreover, if we stop the comparison at the LF human hearing threshold of 20 hz, then its only 2.5 hz difference: 20hz/response -9 db/spl 113 db vs 22.5hz/ -8 db, 114 db, giving a 1 db edge on both items to unassisted box, but at 2.5 hz higher. Not meaningful either way in my view.

Kramer/Timbers mentioned for their 300W 2245H boxes vent diameters of 5 7/8" (divided in two 4 1/8" or so equivalent vents seen on picture in original Audio magazine article I have) for 8 cu.ft. box, Fb 26hz, assisted box, and 9" dia. for both assisted (Fb 20hz) and unassisted (Fb 25hz) 12 cu.ft. box. No flared vents here.

They also stated "nominal maximum amplifier power guideline of 800 watts apply" (P.7) for the 2245, more than 2.5 times Pe (I know they used much higher power than that but said "at your own risk"). No concern here regarding the 2245 ability to sustain such program material peaks. But I am a lot more worrying about the 5 7/8" (or 2 X 4 1/8") port's ability to keep up delivering correctly at very high levels of 300-800 watts...

Dickason made no mention of vents for 18" drivers in his Loudspeaker Cookbook 5th ed., while he did mention 6" dia. ports are good for 12" and 15" types (p.53). Yet, If one extrapolates his own port size classification logic described, then one 6" vent would be usable but minimum for 18" woofer. Its difficult to reconcile a 5 7/8" vent dia. (split in two) here with very high power and port compression, specially at the very low frequencies involved... Larger diameter tubes, such as the 9" dia. port used in the 12 cu.ft. box, make more sense to me, though one reason for using a larger size vent was definitely the lower Fb of 20 hz on assisted box VS smaller assisted cabinet's Fb of 26hz. Fb is an item considered re minimum port area, whereas cabinet volume is NOT part of the vent's minimum required AREA equation, but Vb is part of the port LENGTH calculation. More on this later.

Finally, I have an issue with the response curve shown by JBL in post # 26 for the 12 cu.ft. Fb 20 hz assisted box (4th doc.) and response data in the relevant computer printout (5th doc.). For the 8 cu.ft. Fb 26hz assisted box Kramer/Timbers didn't show a response curve, but their computer printout of response data (p. 3) raises the same concern. Above, I've used the numbers at face value in absence of better ones.

I believe the response curve and data given do not reflect assisted alignment, as it should. These B6 with boost/cut filter should "... return the response back to a roughly flat condition ..." as Keele mentions and shows in his paper (P. 356). Obviously, this is not what we see in the above-mentioned documents. What we get are pretty dropping responses as a result of the low box tunings with no EQ boost. Plus the response curve for 12 cu.ft. 20 hz box shows no "knee" in the LF curve, as opposed to the curve for the 12 cu.ft. unassisted 25 hz box (this one is correct, but tuned a little too low in my view).

The "offending" curve and data are not typical at all of B6 response, i.e. relatively flat LF followed by a steep drop (as in posts # 11 & 29). Here its more typical of lower tuning with no EQ, than anything else.

Considering this matter, the accuracy of the db comparisons/results mentioned above for the assisted boxes should be taken with caution. In my book, they can still be SOMEWHAT compared but all should be considered as unassisted alignments I think, with two of them tuned lower than normal...

Next post getting closer to completion, should follow soon.

Richard

EDIT: Two examples to illustrate the offending data. For 8 cu.ft. assisted box boost applied at 26 hz so response should be about flat there, but at 25hz (closest point in the data) the printout shows its - 8.9 db. For 12 cu.ft. assisted box boost applied at 20 hz so again response should be about flat there, but at 20 hz the printout shows its - 9.4 db. However, the displacement and thermal limits indicated on this printout appear to be compatible with typical B6 alignment...

Ian Mackenzie

03-25-2018, 12:55 AM

For benefit those who might be following this thread please refer to the attachment below.

To clarify some issues raised by a Richard the actual computer printout in the article and posted by Rob is the raw data of unassisted alignments before any electrical boost is applied.

This is confirmed by the alpha ratio that is validated with a simulation of f3 of the unassisted driver.

On the next page a graphic demonstrates the low frequency the response for the 8 cu ft3 ( unassisted and) assisted alignment which was the primary focus of the article (see attachment below).

There is no mystery or missing gaps.

If anyone has any questions please send me a pm.

RMC

03-25-2018, 08:27 PM

First, thanks for coming back again, we knew and said it wouldn't be long.

I gladly accept my mistake of forgetting about Fig. 5 in the article. MEA CULPA FOR MY OVERSIGHT OF FIG. 5 THREE PART RESPONSE CURVE. That should forgive me I guess, plus it does feel good. Try it.

On the other hand, your post sure doesn't explain credibly the outstanding issues and the why of these.

Re "assisted alignment which was the primary focus of the article" good. Then why publish only "raw" unassisted data as you mention? Instead of the more relevant assisted alignment data. Pretty contradictory it seems. It would be much more logical, suitable and helpful for speaker builders, in an article again with primary focus on assisted alignment, to show the DATA RELATED TO THIS FOCUS (i.e. B6 or so alignment), not data for out of focus matters, which btw can be nice in a JBL made comparison of the two operating modes, failing which, as I did with available but "distorted" data, followed by a word of caution and explanations from me.

As for the 12 cu. ft. 20 hz assisted box, also described along with plans in the article, the related JBL computer printout is not in the article but was posted in post # 26 and shows the same shortcoming. However, here the excursion info given on that printout confirms even more my next paragraph below (with evident max output capability loss shown on lower than normal Fb).

In the two curious printouts (8 & 12 cu.ft. assisted boxes), JBL DOESN'T show normal or usual "data of unassisted alignments" as you imply or pretend (like 12 cu.ft. 25hz unassisted box does, yet I commented on), but rather shows data for HALF of the two-step "Step-Down" process, with the lower than normal box tuning INCLUDED, but EXCLUDING the other half of the process being the electrical filter's boost/cut to be applied... So this data is "distorted", though somewhat "unassisted data", showing halfway done step-down process. Pretty meaningless and not very helpful for speaker builders, as it results in a poor "unassisted alignment", except in a few cases, such as the following.

In practice, very few persons [not even in posts # 11 & 29 (red curves), 36 (yellow curve) and 47 & 81 (your own curves!)], would model this box as it was in the printout, with that response curve, except for 2-3 boundaries placement, or if someone knows ahead of time that boost/cut filter assistance is on the way for the box, therefore correcting the deficient LF response. The evident problem here is the more than relevant data and/or curve never came...

RE "This is confirmed by the alpha ratio that is validated ..." I think you'll have to find something better than this considering what this ratio is all about: "... because alpha = Vas/Vb and neither of these volume parameters..." (Bullock, P. 24). Since this is related to box volume calculations, and proper box volume/size ISN'T even an issue here, it looks more like "techno filling" in the present context. Hint: try another ratio.

RE "There is no mystery or missing gaps." Well, look and read again as you clearly haven't explained the outstanding ones, Plus you just added another.

RE "those who might be following this thread", as you can see, during your silence, a good 700+ views were added in a short time, which confirms again many do enjoy the thread. Including you watching it not only because its interesting, but also in case I forget something...

Bottom line, the only thing you could find is the forgotten Figure 5 by me, that I willingly accepted above. This means its not bad at all for the rest of the article...

Thanks for showing interest in the thread again, and each time you come back. Keep-on clicking and liking it.

Richard

P.S. Any progress on the LE8T/4311 Thread?

EDIT: RE "as it results in a poor "unassisted alignment", except in a few cases" above. In that case, the poor alignment is one with no EQ boost, lower than normal Fb, giving non-flat and pretty falling LF response, accompanied by unnecessary cone excursion, leading to more distortion. Not much benefits here...

Even with more boundary placement, I'd prefer to stay away from the above scenario. In a pinch, if one is stuck with such a box, that he can't/don't want to re-tune higher, then 2-3 boundary placement could be somewhat of a LF "savior" for free!

Its much preferable to model the box properly from the start with a flat or so alignment (it doesn't have to be maximally flat), and if need be, then use more than one boundary placement to add room gain, as this avoids the excursion penalty and the falling LF response associated with lower than normal tuning.

cooky1257

03-26-2018, 01:56 PM

RE "those who might be following this thread", as you can see, during your silence, a good 700+ views were added in a short time, which confirms again many do enjoy the thread. Including you watching it not only because its interesting, but also in case I forget something...

For the record, viewing isn't liking or enjoying. I'd much prefer to see some of your DIY projects which given all the theory we are bombarded with would at least be interesting to see how you've applied same...

Ian Mackenzie

03-26-2018, 08:32 PM

Zactly.

It’s worse than the emperor without the close.

The posters negativity and hostility toward anyone or anything other than the triad of his ramblings are nothing more than a madman’s plagiarised view of what he said she said.

If nothing else it’s a strong reason for closure of this thread.

Done and dusted.

Further Moderation required
***********************

RMC

03-27-2018, 04:05 PM

RE post # 100:

As mentioned in post # 1 and another time, this thread is Step-Down info gathering oriented, to group it in one place for those who want/need that info. It was never presented nor "sold" as a projects oriented thread. Still on target. No false advertising made here.

RE post # 101:

Thanks for taking the time to click again! Note that while reading a thread's title, I sure DON'T click on those presenting little or no interest to me, as most people do I guess, and even less intervene in them... So the number of viewers shows these can't all be wrong or at the wrong place! Even if your wish is to see it go belly up, as one of your very few did. Or when you tried to revive an old thread of mine with beating around the bush, and I didn't take the bait on this... Looks more than ever like jealousy.

One more time nothing more in that post than your usual noise, attacks and insults, simply because you can't control the thread/info flow, cannot show that its wrong and you're not at the center of it all... I fully agree that "Further Moderation required" for YOUR OWN posts which bring very little or no substance. One can't avoid noting the coincidence between the rapid increase in the number of views and your absence. Viewers are sending a message about your "rhetoric" it seems.

On the other hand, your posts ONLY confirm YOUR own negativity and hostility towards the thread and myself, attacking both at will, as an Emperor does, and doesn't like his "subjects" may respond to these blatant attacks he makes, nor set the record straight when quite questionable info is given... When caught, well the usual insults fly instead of admitting/accepting the error as I did, correcting it and moving on like "educated adults do". The reaction only corroborates the old trick we know.

The best revealing part of all this, that viewers certainly see, remains that you have all the freedom to do your own "pleasing" show in a thread of your own with any of YOUR projects, such as the never seen LE8T and 4311 YOU mentioned, but you still don't deliver as usual. That says a lot about the real intentions and motivations behind the curtain, when time after time one prefers bullying a thread rather than showing his skills in his own thread...

Naturally, the numerous interested viewers motivate me to continue my work in this thread, as there is MORE interesting stuff coming, and you sure won't miss the opportunity to look just in case you (secretly) learn something, or even find a missing dot to criticize. Enough time wasted on this unworthwhile matter.

RMC

04-01-2018, 08:23 PM

E3A) CONE EXCURSION (THIS IS THE FIRST PART OF A TWO-PART POST, NEXT ONE TOMORROW)

The more recent 18" 2269H (Xmax 19 mm, Pe 1,200 w) was modeled at 600W in post # 29 with a 8.9 cu.ft. box, Fb 26hz, in both assisted and unassisted versions. Assisted alignment was with filter Q 1.5 for improved LF response flatness as later explained, instead of the usual Q 2, not a big difference though. Compared to JBL's assisted 12 cu. ft. Fb 20hz 2245H box discussed in my post E2), the present one has higher tuning, smaller box size and boost/cut filter Q 1.5 VS Q 2, both at Fb. This represents a less difficult "environment" to perform. In fact, here the 2269's situation is closer to the 2245's assisted 8 cu.ft. Fb 26hz filter Q 2 box.

The 600W assisted data & custom response curve from the above post shows the almost 8 hz lower F3 mentioned in a previous post, plus about 4 db higher output at 30hz (and about +3 db around 26hz) compared to the unassisted version (+ 4 db being equivalent to 2.5 times power according to Eargle's table). Around 22 hz both curves are basically at the same output level. This modeling, as some others, doesn't show a whole lot of LF gain from assisted alignment for this other "super woofer". Not really surprised by the result considering what I mentioned previously about some of these woofers who appear to reap less (not zero) VLF extension benefit from step-down, than lesser capable drivers. Still a nice 3-4 db output improvement here at 26-30hz.

The "comparable" 2245 assisted 8 cu.ft. Fb 26hz filter Q 2 box, had an F3 of 26 hz and unassisted F3 at 35 hz (9hz gain) VS 24.6 hz and 32.5 hz (8hz gain) respectively for the 2269H. These numbers for both drivers are pretty close to each other. BTW, I left aside for later the different box QL used in the modelings, QL 7 for 2245 VS QL 5.4 for 2269 and its impact on Vb, since I have an issue related to that (not re 2269 modeling).

At the same 600W power level, the vent air velocity curves around Fb, shown in that post, indicate velocity is notably higher for the assisted design which, IN PRINCIPLE, looks normal because of the lower frequencies involved. On the excursion graph we see the assisted 2269, though filter is Q 1.5 instead of Q 2, still shows a left bump a bit higher than the right one, contrary to some other drivers seen here where its the other way around. So this driver doesn't appear to be affected (or is less so) upper range by the small maximum output capability reduction, caused by step-down, in the "region of original box tuning" as E-V calls it. Probably due to driver's double cone travel capability and higher tuning in smaller box than the assisted 12 cu.ft. Fb 20hz 2245H box showing about 1 db decrease. The more comparable assisted 8 cu.ft. fb 26 hz 2245 box didn't show on the printout any output capability reduction either.

However, the cone excursion curves shown, also at 600W, are more of a concern as they bring the question of why the very little cone travel reduction seen around Fb, on both assisted and unassisted versions, compared to other vented box excursion curves?

Looking at a few data sheets for JBL made boxes using the 2269H (e.g. VT 4880A/4881A; ASB 7118/7128 these two btw use triangular type vents I mentioned in a previous post; MD 7 horn loaded, not relevant here), specific vent area or diameter used are not mentioned.

For comparison purposes, I noted the 2245H box example given in its own data sheet is Vb 10 cu.ft., Fb 30 hz and port area of 50 sq. in. This is equivalent to an 8" dia. tube! I modeled the same box in Winspeakerz and got a minimum recommended vent area of 45.7 sq. in. (7 3/4" dia.), reasonably close. Moreover, I've done another simulation for the same driver in the 8 cu.ft., Fb 26 hz, QL 7 box where the software tells me the minimum recommended vent area is 39.6 sq. in. or just above a 7" dia. port (38.5 sq. in.) VS JBL's 5 7/8" mentioned before.

By the same token, I modeled the 2269 in the 8.9 cu.ft. Fb 26 hz QL 5.4 box to see what would be the software's minimum recommended vent area for this one: 75.1 sq. in., close to a 10" dia. port (78.5 sq. in.) or to 2 X 7" vents (77 sq. in.). This looks pretty large, but remember this is a very high excursion (included in Vd calculation) 1.2 KW rated driver, modeled in post # 29 at half Pe (or double that of 2245). Nothing wrong with this, but "the pedal isn't yet to the metal" as there's still 600 more Watts to go (+ 3 db). And we haven't even mentioned the program material power/peaks (e.g. see JBL ASB 7118 data sheet).

If one finds such vent size(s) really inconvenient and has no intention whatsoever to use the driver anywhere near 1.2 KW, sure someone can get away with less port area at lower spl. Then you'll need to model accordingly in software with a lower driver power rating number in order to see what you can live with: vent size vs power. If you end up selling the cabinets one day its not a good idea though. Buyer looking for a very high power box gets so so vent capability (i.e. compression and noise at high level).

The second part of this post should follow tomorrow. It is written but I need to review it and add bits and pieces.

Richard

RMC

04-02-2018, 08:30 PM

E3B) CONE EXCURSION (PART TWO)

With regards to potential port compression in view of the cone excursion curve shape at 600 Watts shown in post # 29, I note the port diameter used in the modeling is 6" with two flared ends, more aerodynamic profile improving air entry and exit of the port. However, that doesn't change vent tube diameter required. It's still better than a standard straight vent (with "ifs and buts"), as show Salvatti, Devantier and Button.

In comparing both 2245/2269 port dia. info in my preceding post, the 6" vent used in the 2269H modeling appears too small considering the more or less 7+", 8", 9" and 10" vents mentioned for the 2245 or 2269, in order to minimize port compression at high spl. This quite possibly explains the pretty small cone travel reduction effect of the vent around Fb for the 2269 box in post # 29. If a 7+", 8" or 9" dia. vent tube is the way to go for the 18" 2245, then the 18" 2269 with much higher power and Xmax may very well justify the even larger 10" or so vent. There isn't a large Sd difference for the two drivers (.129 vs .123 sq. M.) but the very large one on Xmax gives the 2269 a notably higher Vd (1.23 vs 2.33 L) 89% more! (Sd x Xmax = Vd).

I extrapolated previously Dickason's vent size use classification, showing 6" dia. port would be usable but minimum for 18" drivers. This also depends on Fb and power input. The deeper the Fb and the higher the power, the closer trouble gets. In the specific modeling reffered to, power is very high and Fb pretty low, hence the issue. Driven with less power and/or using a higher Fb, would probably result in being able to get away with it, up to the point where the temptation of ever increasing the volume control gets too high...

I also did a quick modeling in Winspeakerz for the same 2269 box, but with the recommended vent area (75.1 sq. in., about 10"dia. port), and varied power input at 10, 100, 300, 600 and 1,200 watts to see the effect on excursion curve shape as power increases. The results I got, even up to 1,200 watts, are more typical of vented-box excursion curve shape with a "deeper diving" curve at Fb (i.e. more cone travel reduction). I believe this tends to confirm the port issue raised here regarding such 6" dia. vent at high power.

The minimum vent dia. formulas (e.g. R.H. Small; M. Engebretson) consider Fb and Vd to determine the maximum amount of air that will need to pass in the port. Port diameter is then determined as the minimum requirement to avoid port noise. In practice, input power level acts as a "modulator" of cone excursion level, which in turn varies the air flow in the port tube from a very low up to a very high amount.

While we're on the subject of a very high power/output driver, out of curiosity its interesting to learn from the same three Harman Engineers, how bad vent compression can get at some point: "Extensive benchmarking of current designs reveals that current attemps at high output ports suffer from compression effects at high drive, showing that at very high levels all ports eventually "lock up", limiting the maximum output. (...) At these levels the output from the port is 180° out of phase with the output of the cone, creating a nearly complete cancellation of low-frequency energy." (P.19, & 23) (!) In addition they mention "Also at lower frequencies (higher velocities) the effect [RMC: compression] is much more pronounced."(P. 29) So the quest for ever deeper and higher SPL bass has another obstacle on its course...

If you can get a clear picture of the JBL HLA Series 4897/A subwoofer (4K US$ in 1997!), as in the 1996 color Brochure, or in sketches shown at the end of data sheets/technical manuals, the unusually looking vent is a sample of JBL's work done on newer very high-power vents: very large rectangular or so with rounded corners and flared ends. In a way, the concept of the round flared vent, but increased substantially and adapted to a very high-power box.

The 4897/A's pretty large vent in close proximity to both woofers happens to coincide with Dickason's experiment where his larger vents "... very close proximity to the driver seems to cause the least amount of disturbance." The smaller of his vents having less problems at a distance from the driver, and double ports producing less problems when at a resonable distance from each other. (P. 55). The above should give viewers more food for thought.

Finally, the point here is the use of "super woofers" involves knowing much more about some important related issues behind the curtain, and seldom mentioned, in order to achieve or use a super driver's full potential. In my view its nicer to know ahead of time what this may entail, such as:

e.g. Speaker builders have to realize at these extreme power levels there's no room for flimsy cabinet construction. It must be "built like a tank", extremely strong, heavily braced and sound dead when hit with a mallet to avoid any panel vibrations at very high spl. In the 2006 Vertec subwoofer/2269H press realese and other docs, JBL mentions "The enclosure features advanced construction techniques, replete with JBL PlyMax engineered panels...". That should give some idea about the requirement.

Also, the amount of work involved to make or find a proper high-power vent(s) should not be underestimated, unless one is lucky to find the appropriate ready-made device, which may not happen.

More to come.

Richard

Robh3606

04-03-2018, 06:41 AM

Also, the amount of work involved to make or find a proper high-power vent(s) should not be underestimated, unless one is lucky to find the appropriate ready-made device, which may not happen.

All you need to do is use the cardboard tubes used when you pour concrete footings, Great for sealed midrange enclosures as well. Any Home Depot or Lowes will have them They come in a wide range of sizes that you can pick through to find the closest match.

Rob:)

Ian Mackenzie

04-03-2018, 12:31 PM

The DD67000 port assembly is cast aluminium

I have seen a 15 inch port on a 2225 system many years ago.

In Alex Bradminoff and Don Davis red loudspeaker book they make reference to vent area equalling cone area

A port can be constructed out of timber and baced where one enclosure wall forms one side of the port

Perhaps a point to consider is pipe organ resonance with long ports and volume occupied by large ports

A port should be ideally at least one diameter from any enclosure wall
If you consider enclosure construction then the practicality of large port area becomes a limiting factor

I think the associated concerns of power compression points to the use of multiple subs where the total power is divided across 2 or more subwoofers. For example 1000 Watts into a voice coil is on the spectrum when a large portion of that is lost in heat. Stacking of subs then becomes a reality.

Others claim tapped horns are more effective at high power levels

I once heard Steve Schells bass horn
On just a tiny digital amp it was dynamite. Deeper, faster and more dynamic than any bass reflex system
I would not mind hearing the OMA bass horn with a 21 inch driver

RMC

04-03-2018, 03:55 PM

RE POST # 105

The suggestion definitely has merit in the absence of a best or second-best thing. Here's why in my view, as I like to know the reasons for choosing between different options.

Having dealt with some 8" of those a while ago, I'm not sure though its thick enough to avoid resonating at the very high powers involved... I don't remember their thickness, but I seem to remember (right or wrong) its a bit flimsy not very sturdy? I'll need to check that next time I go to Home Depot. On the other hand, in the world of vents using larger dia. often means longer port tube (e.g. post # 26, 12 cu.ft. 2245 box, 9" dia. vent, Lv 20" and 30"!! with "Duct screwed into bottom and side of Enclosure". First time I ever see that, seems contrary to some vent advice, but anyhow). Longer vents are more prone to resonance. Yet, I still don't discard the idea.

However, this was not exactly the type of vent I had in mind when I wrote my post. What I had in mind, and should have been more precise about this I guess, is the type of vent mentioned a little higher in my article and used in the JBL 4897/A or something similar, or with the same virtues. I know that's a damn big order, this is why I wrote at the end "...unless one is lucky to find the appropriate ready-made device, which may not happen."

I did check in the 4897/A Technical Manuals specifications beforehand as pretty often vents of JBL made boxes have a part number, though besides that it usually says NOT FOR SALE... I did the same verification for 4897 vent just in case to see if there's a part number for that, hoping (a dream) that MAYBE such could be available ? Not a chance! I couldn't see a part number for the clever device and it appears to be part of the cabinet. Strike out # 1

Failing which, large round flared vent(s) certainly come to mind as second best. But in this case one should read the Salvatti, Devantier & Button article on ports, at least for the parts understandable by non-Engineers, to avoid wasting money on "unfit" flared vents or to increase the chances of getting something worthwhile for the dollars spent. Again, at the very high powers involved here, one doesn't need nor want a donkey...

After looking into that paper, one may wonder if the commercially available flared vents sold left and right have the required Engineering built in/can really do a nice job or is it partly hype? The concept is certainly good, no doubt about this (as shown by Salvatti & al.) but the execution of that, mass-produced in China in "all shapes and sizes" (!) for the majority?? Most of the time there's very little, if any, technical info given on these, other than dimensions and type (flanged or flared). BTW one well-known retailer of these, I'm looking at now, sure doesn't know his knee from his elbow, as it wrongly describes many of both types in product descriptions, with no tech data... Its gonna be a long way! Strike out # 2

Bottom line: for most people its either your idea/or equivalent (i.e. multiple smaller vents) or taking a chance with some round flared vent(s) of unknown properties/specs. Personnaly, at this point I'd probably go with the former instead of the latter...

Richard

Ian Mackenzie

04-04-2018, 10:57 AM

Hi Richard

Else where you have posted that QL losses are largely enclosure leaks and not attributed to losses from other sources.

(Regardless of small or large signal analysis any port noise, port power compression that can
be actually measured compared to the theoretical ideal must be a loss.)

That being the case your most recent blog on ports seems to be a contradiction of your earlier writing?

(Btw why have you not posted a link to where someone can read or buy the paper? Your take on the document may not be the same as an experiment loudspeaker builder?)

Perhaps you forgot what you previously said or you think a port is not a good port unless you understand the paper above?

Before you fly into another blog you might be well advised to leave out your own “ judgments “ and let the findings in these references be available for those interested to draw their own conclusions.

RMC

04-11-2018, 09:10 PM

RE POST # 108

Thanks again for clicking on the thread and dropping in consistently we are flattered, as it shows your personal attachment to the thread. We know its getting more and more difficult for you to fake its a lousy thread considering the 5,500+ views. Plus you just can't beat, nor match it with LE8T/4311 stuff...

Looking at your posts one can hardly find any meat, other than the usual go around, dubious claims and beating around the bush.

As for a post regarding QL losses you sure didn't have the guts to show the full original post, like you didn't with what Keele said either, which anyone would normally do to at least try to support what he claims. Not you though, as it may not have served your purpose here by not saying what you pretend... Perhaps it was more "convenient" to make your own "romanced" interpretation of post?

BTW had there been a millimeter of "contradiction", and there isn't, it would have been quite easily and logically explained and understood by anyone, but by your own writings its evident you haven't figured it out yet, or just trying to create the regular controversy that doesn't exist.

In fact, the only contradiction that does exist is the one with your post # 101: "If nothing else it’s a strong reason for closure of this thread. Done and dusted." And you're still here! Definitely, the thread IS quite attractive!

Cheap way to use others as bait or pretext in trying to get, in reality, an easy free copy of the paper for yourself. Its available, coordinates too, but you're just too busy with the fake news to find it. Since you won't really read it, as is evident from you're "reading" of Keele's paper, you might not really need this one. Those who genuinely need or want the paper have probably found it by now. The sudden "circumstantial interest" about the paper is quite revealing about the intent.

As many know already, I don't have a habit of copyrighted material infrigement and violation of author rights, as some others do left and right. "Who cares" will be your answer to that too? Up until such time where there will be no more quality writings available... Quoting from a text for illustration and/or explanation purposes IS permitted as long as reference is mentioned, as I do.

"...experiment loudspeaker builder?)" My understanding on this is that you're talking about others, not yourself, right? Considering many probably have found it already, but not you.

"...you might be well advised to leave out your own “ judgments..." Sounds pretty much like the Emperor is back again, doesn't it? He who's own posts are filled with unsubstantiated judgments and claims! Does that mean you'll follow your own rule or is it good only for others ?

RE Post # 106

"In Alex Bradminoff and Don Davis red loudspeaker book they make reference to vent area equalling cone area"

Though initially this may have some merit, there's more to it in real life that was not mentioned here...

If you knew the book a little more, first it seems you would have noted that "Bradminoff" is in fact Alexis Badmaieff, second the "red" book is called "How to Build Speaker Enclosures", third and best of all is it was published in 1966 (books.Google.com and Amazon.in) or 1967 (Amazon.com) for hardcover. Paperback version 1970?

Not exactly a contemporary reference or a more recent and preferred vented-box Loudspeaker Engineering book or article. Also, issued before R.H. Small's monumental vented-box work was published in JAES in 1973 or so, followed by many other more current articles/books by various people with varying scopes and magnitudes...

"I have seen a 15 inch port on a 2225 system many years ago."

It sure looks impressive when said, but while mentioning 15" port use one should check, also inform, about the feasibility of this practically speaking. Knowing that is even nicer. Since you don't show having done the verification, its a good thing that JBL did cover this issue many years ago:

"... the largest practical port should be used. Computer listings of port choices calculated to limit air velocity inside the port duct will list duct sizes which are normally impractical. A 380 mm (15 in) diameter port is not an unreasonable choice for a 380 mm bass driver, however the necessary length would dictate that such a port might itself have a volume of many cubic feet, sometimes equal to or larger than the original enclosure." (JBL, The most commonly asked questions about building enclosures, from Q. 11, P. 4 of 10. Document not dated, but I've had this since July 25, 2001, date printed; Drew Daniels of JBL may well be the author of this as he wrote a paper with the same title, mentioned in the present one, the latter would appear to be subsequent).

Hence my previous mention of Harman Engineers indicating : "... the largest port area allowable by a given design should be employed..." (Salvatti & al, p.43).

The JBL recommended min./max. box volume for the 2225H is 3-10 cu.ft.(cf), and a box tuning of 40 hz is suggested in two of their papers (see 1). So I modeled in Winspeakerz (QL 7, Half-space) what would be the effect on vent length (Lv) with a constant 15" dia. (176.7 sq. in.) port and tuning frequency of 40 hz, while varying box volume from 3 to 10 cubic feet.

Results I get: 3 cf Lv 88.65"; 4 cf Lv 63.75"; 5 cf Lv 48.81"; 6 cf Lv 38.85"; 7 cf Lv 31.73"; 8 cf Lv 26.4"; 9 cf Lv 22.25" and 10 cf Lv 18.93".

So the shortest vent length would be 19 in. long, that in a 10 cu.ft. box, in which JBL doesn't normally use/suggest the 2225. Instead: 4 cf in Enclosure Guide, 5 cf in model 4507 and 4 cf in the second reference below. The cabinets larger than the preceding are usually specified for other single woofer, e.g. 2240 (6 cf); 2240/2245 (8 cf, as in model 4518); 2241, 2242 and 2245 (10 cf).

Practically speaking, in the type of box volumes the 2225 is typically used, the vent length for a 15" dia. port would need to be at least 4 feet long. Stretching it to 6 cf the vent is still one meter long or so. We have not even mentioned the resonances issue here.

Obviously there's other material that my faithful fan probably doesn't know about, so I will continue my work with another informative post (including some vent stuff!). This way he can keep coming back, though right after someone else came just before him, as he does, to add his own two cents...

1) JBL Pro Enclosure Guide p.1; JBL, Vented Loudspeaker Enclosure Construction and Operation, P. 4.

grumpy

04-12-2018, 06:37 AM

Perhaps more DIY and less GFY.

Lee in Montreal

04-12-2018, 09:01 AM

Ian Mackenzie

04-13-2018, 02:13 AM

Nothing l post is ever taken seriously to the point of going “Off Beam.”

At any rate it’s a public forum and anything is open for discussion or debate on any thread.

The forums are NOT a democracy.

Of more amusing tone if l was attempting to collate numerous papers wall papered around the house because l ran out of desk space l would probably fuck up writing about “what he said she said “ more often then not so it’s fun to call out continuity bleeps when they surface.

RMC

04-13-2018, 11:44 AM

Hi Grumpy,

Thanks for visiting us. More DIY is certainly a possibility. Especially in consumer speakers, manufacturers seem to prefer showing 3 smaller vents than a larger one for example. Big hole in a box doesn't look good and is less practical configuration wise. Marketing is king as some say.

However, DIY or otherwhise the issue with extra long vent remains when the port diameter is "excessive". Unless one uses a pretty large box of say 10 cu.ft net in the present case. But then this large Vb for a 2225 presents another issue with the driver: getting a proper alignment, with an acceptable response curve.

Since I modeled 8 boxes one after the other for purposes of seeing Lv changes only, not for nice alignment or frequency response appropriateness, I didn't spend time on that aspect, though I did look quickly at each curve generated just to see, but I don't remember exactly each one for each Vb used.

I do remember seeing, in the frequency responses, some where the woofer was not really "at ease" in the box, showing sign of being "overstretched", i.e. getting further away from a somewhat optimal or a reasonably flat LF alignment.

If some folks like it this way, good for them, since its their money and gear. I've seen on this site a number of months ago a fellow using a box tuned lower than normal (as in step-down mode) with no boost/cut filter. Though there are good reasons, mentioned, for not doing this, he liked it this way, although the system may not be performing as it should or could (room gain was not in the picture). Fine then.

Sometimes (also seen recently here) some fellow trying to get deeper bass type of performance from a less capable or inappropriate woofer, just by increasing box size and being confident this would do the trick (bigger being better in their mind), with no step-down mode involved. Even if there's more to it than just that, but this is another matter.

I sure would not use a 2225 in a 8-10 cu.ft. enclosure for example, whereas others may. Folks can certainly build whatever they want or like since its their own thing. In my view the most important issue is, as long as they have the relevant info on a situation, at least they can make an informed choice, optimal or not, and know why...

Regards,

Richard

RMC

04-26-2018, 04:16 PM

RE Post # 112

No new technical matters there, as usual. But he remains the thread's most faithful fan and supporter regardless of his go around...

"Nothing l post is ever taken seriously..." This is certainly the most interesting statement from the poster, along with "...l would probably fuck up writing..." Quite conscious revelations! "Off Beam" or not, and straight from the horse's mouth!

The above statements sound pretty much like the poster is telling us viewers around here consider him more like an entertainer, a comedian role playing, or an actor trying to get attention with stuff not to be taken seriously.

Then, poster should look at himself about the credibility issue HE raises and the why of not being taken earnestly. Often people build their reputation themselves, with their own acts. Could be a message the viewers are sending.

"At any rate it’s a public forum and anything is open for discussion or debate on any thread."
Anything, anywhere, being good enough just to create fictitious debate in threads, regardless of facts? Is that the mission statement?

"The forums are NOT a democracy." Well, he sure added quite a few "votes" here. With numerous options to choose from on the "ballot", and consistently choosing this one freely, one can't avoid seeing this as real democratic support on his part. Can't get anymore democratic than that, since in totalitarian regimes there's only one name to choose from...

Sure quotes from knowledgeable sources in audio bug him a lot, particularly when stories told don't match with reality and audio engineering. When a bleep really surfaces or rather when he THINKS he sees a bleep because he doesn't understand, or fakes the imaginary one for convenience?

Nice try, but even more amusing is the fact he still hasn't shown any alleged "contradiction", nor any LE8T/4311 stuff btw, that HE said people want to know about! As he won't deliver on these, he could still be debating the stuff with himself and show his skills while doing it. No wonder he's not being taken seriously...

RMC

04-26-2018, 04:17 PM

F1A) CONSTRUCTION DETAILS

The fellows wanting to clone boxes mentioned in the Kramer/timbers article regarding assisted designs or not should look closer at the construction details and box volumes given in that paper as some of that stuff doesn't seem to make sense in real life. I don't know if someone here has raised these concerns in the past, but here are my issues.

There are basically three cabinets identified in the article: 4.5 cu.ft./2235H (equivalent to B 380 subwoofer), 8 cu.ft./2245H (equivalent to B 460 LF speaker) and 12 cu.ft./2245H box in two versions, the difference between the latter two being the duct length. The boost/cut filter used in some isn't a box physical issue covered here, but rather an electronic equalization matter. The box plan in post # 26 gives more details on the 12 cu.ft. cabinet than in the article.

In the construction details given on page 5 of the article for the 8 cu.ft. cabinet, one-inch thick particleboard is recommended, 50-pound density or more, "for the requisite acoustical deadness". The panels should be braced with 2 X 4s. There is no front to back brace used in the plan, e.g. from the baffle brace to the back panel brace, I assume since it would not be centered because of the woofer. Still a rigid box considering the 1" material and the 2X4s.

The construction details of the 4.5 cu.ft. box are the same, except vent, 3/4" thick material use and "For the smaller panel sizes of this enclosure, 1 X 3-inch braces are sufficient." P. 7

Things are getting more "slippery" for the 12 cu.ft. one, when compared to the above two boxes... Even though at least 3/4" material is indicated, the plan was in fact made with that material thickness, and no mention of Baltic Birch use for example. As for the panel braces, they're all 1 X 3 inch pine mentioned on the plan. A 50% larger box (12 cf) gets thinner panels and bracing than an 8 cf enclosure with the same driver!

The 12 cu.ft. box has an Fb of 20 hz in the assisted version (thermally limited down to 18 hz!, except for a 1 db or so restriction on a 10hz portion, as mentioned before; all this subject to my earlier mention of halfway done step-down data). This is 5-6 hz lower Fb than the other boxes mentioned here. Now, if one compares box sizes involved (4.5, 8 and 12 cu.ft) with the construction details given above and the lower frequencies to be reproduced, the latter one's material/bracing is quite questionable. Someone dropped the ball at JBL?

3/4" and 1 X 3" might make sense for the 4.5 cf enclosure. Yet It wasn't good enough for the 8 cf box, but its presented as if it is sufficient for the larger 12 cf cab, both using the same 2245H. Since larger panels are more at risk of vibration than smaller ones, it seems logical to me and technically sound to indicate the use of 1" material and 2X4s first and foremost for the 12 cf box, instead of the 8 cf box, or for both of these. The "requisite acoustical deadness" certainly applies, even more so, to the largest of the boxes...

Cloning enclosures looks nice and easier considering the ready-made recipe. However, one should still use judgment in the making, as some recipes would likely require nuance or fine tuning.

More to come.

Richard

Lee in Montreal

04-26-2018, 06:32 PM

Dear Richard. You do not realize how annoying you are with your self pumping ego as all you do is copying articles off the net. Have you developed anything? Did you reach a breakthrough? What did you build? Effing nothing is the answer. Is there any point to your latest rambling or is that your ego feeling hurt? Come on. Stop being pompous. You're ultra annoying. Oh, and people don't contradict you simply perhaps because most people don't even care. Did you realize that? :applaud::applaud::applaud:

Ian Mackenzie

04-26-2018, 11:56 PM

http://www.audioheritage.org/vbulletin/showthread.php?40531-DEEPER-BASS-D-B-KEELE-E-V-s-STEP-DOWN-MODE/page2

Hi Lee can l suggest the ignore button. As long as “it” pontificates here in this thread and stays away from populated public places no one will ever care:

The above link states at least 3/4 inch particle board or void free plywood.

At “least” being the point.

I do agree with your comments.

The reality is RMC has come to these forums with no familiarity of Jbl product or heritage.
The critical and rather judgmental postings have no real substance or plausible merit.

If anyone, a “ normal “ person identified real mistakes or short commings in an article they would first seek validation by their peers. They would then make an effort to contact the authors for comment and feedback. He does not do this because there’s no real basis for the criticism. It’s just slanderous negativity.

The inflammatory nature of the postings is such that when l did post feedback from DB Keele Jnr with approval of the administrator on how the step down tuning works he launched into a personal attack and vendetta.

The official feedback was Really?

He just being a little prick because he enjoys it.

Ian Mackenzie

04-27-2018, 03:10 AM

DES-1

04-27-2018, 06:19 AM

can l suggest the ignore button.

AH, that's where the ignore button is
80964

Ian Mackenzie

04-28-2018, 02:44 PM

In reference to comments made concerning baffle panel thickness and bracing dimensions my suggestion is as follows.

Follow the article holistically. Read the text with the plans and study the notes on the plans carefully. The article gives recommendations for construction and offers latitude for a choice of enclosure options. Minimum material requirements are given.

http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm

On Interpretation of the different plans one needs to appreciate the mass (weight) and practicality of moving a 12 cu ft enclosure using using thicker panels and bracing than the minimum specified. Note the bracing has been scaled to the panel thickness it is fastened to. There is absolutely no point making something you can’t move! (Ref post 26)

Those of us with real practical experience who have been down the path of large enclosure construction can guide anyone interested in these types of enclosures on the forums.

The JBL Library has some great references for enclosure construction.

http://www.lansingheritage.org/html/jbl/plans/jbl-plans.htm

Ian Mackenzie

04-30-2018, 12:52 PM

Below is a link that took about 25 seconds to find on port design and flare design.

What l like a about this link is someone has actually done some experiments (the work) recorded the results and concluded with a port-flare calculator. The article is well written in and easy to follow.

http://www.subwoofer-builder.com/flare-testing.htm

http://www.subwoofer-builder.com/flare-it.htm

RMC

05-23-2018, 10:11 AM

RE POSTS # 116 & 117

Following the path traced by faithful followers, the reply along the same lines.

The first one's noise is certainly a pretty good description of who he is and what he does (the hat truly fits him), grabbing/copying other's stuff off the Net, TONS of pictures, graphs, charts, response curves, sketches, etc. and re-posting them with little or no value added, nor mention of source. His most significant audio achievement is copy and paste buttons. King of "Picture audio". He hasn't realized yet he was writing about himself too busy trying projecting it elsewhere. Its also revealing to see he's not annoyed by his buddy's own ramblings! Btw those who don't care aren't annoyed, they're elsewhere...

As for the other's ramblings, his "reality" is nothing more than his virtual reality show he stars in. "Really?" From savior buddy to the rescue, as expected no surprise there. "Prick"? He sounds pretty familiar with that, he taught me, learned from him the master. It takes one to know one, right? Furthermore It shows how desperate he is, being out of feasible or valid arguments, to "debate" as he says...

Seeking validation by peers and contact of authors? Pursuant to that logic, same rule would apply to those who criticize JBL's new products should seek peer validation and contact the Co. before to clarify the matter? Those criticizing JBL's direction change, and in particular the ones attacking Paliwal should do the same peer validation plus contact Paliwal, right? Did he comply with his own rule? Seems he's "forgotten" to mention the "negativity" of quite a few. Logic that simply doesn't fly...

Plus he certainly disregarded his own "ignore button" suggestion to others, LOL, as he just loves coming back, FOUR times after his own advice! to the thread he's faithful to. The first time to edit his post, adding more of what he knows well: made up stories and fake news. Seems that "normal people" he uses don't keep making a fool of one's self...

First he was against step-down and the thread (i.e. relevance), then became favorable to it, later switches back to being against it (i.e. thread closure), and now in post # 118 is backing it again with the same "Keele news" (though 25 years ago that idea was already in EV's 1993 TL 3512 data sheet that HE posted earlier!), as being the only post (his) that matters in the thread! Talking about large ego? Changing direction like the wind, showing the level of seriousness. Depleting his own credibility...

When caught up by their own things they get all frustrated, bullying with the customary low ball and name calling, like teenagers do. No doubt its frustrating when one plays the "experience" card and "seniority status" but in reality knows a lot less. They still haven't tried competing the thread with stuff THEY raised. As "experienced" as they claim, with two of them it should have been a piece of cake. Nothing though...

Bottom line, they rarely have real meat to deliver. They prefer teaming up to play their usual game of seeking "status" recognition and bogus "experience" attention. Buddy helping/saving buddy from the corner he paints himself in frequently. They hang around together, filling threads and complimenting each other, then save each other's rear end, regardless of merit, earning low credibility. Bailing out the other when the low value stuff they post catches up with them. Audio's entertainers...

I treat people the same way as they treat me, often playing by their own rules, along with their own pompous language. These sure don't like whenever what they serve is being served back to them, as large egos don't. When they throw punches, I punch back. When one throws mud, he has to expect receiving some too. If not, well they know what to do...

RMC

05-23-2018, 10:18 AM

RE my: "Even though at least 3/4" material is indicated, the plan was in fact made with that material thickness, and no mention of Baltic Birch use for example."

The note below Fig. 10 on P.6 of the article indicates "Exterior dimensions shown produce correct interior volume when 3/4-inch board is used for walls; ..." Looks pretty clear what is the intended material to use.

"B.C. Fir" 3/4" 7-ply wood is said to be void-free by some. As I have two pieces on hand, I can say I see no voids on the perimeter, inside?, but that sample is too small to certify void-free. Moreover, "Douglas-Fir is very stiff and strong for its weight, and is also among the hardest and heaviest softwoods." (From the Sitka Forest products Web site). Still away from Baltic Birch plywood in terms of density and rigidity though.

Since "those of us with real practical experience" sets the tone, we'll follow the pattern. Those who know, know that panel thickness is rightly adjusted to box size (e.g. E-V's mention that about 2 cu.ft. or less boxes can be successfully constructed of 5/8-inch material." Pro Sound facts, #7, P.8).

Re post # 120, sounds less convincing and helpful going from "At “least” being the point.", on to "follow the article..." (i.e. 3/4" use), then "offers latitude for a choice of enclosure options". The only physical box options given in plans and article are board thickness (the "at least") and the vent length depending on tuning frequency.

The relevant issue mentioned, the weight factor, being in practice that of a 15.5 cu.ft. exterior box volume. Whether one uses 3/4" or 1" particle board or Baltic Birch or equivalent, a cabinet of this size and material will remain pretty heavy when loaded. Space taken by such a large box is another item mentioned further. Box too large? Then one can take advantage of an assisted alignment and benefit from a notable 4 cu.ft. reduction in size as shown by Kramer/Timbers: assisted 8 cu.ft net Fb 26 hz VS unassisted 12 cu.ft. net Fb 25 hz.

As for "bracing has been scaled to the panel thickness it is fastened to.", in the present context this would mean thicker panels go in hand with thicker bracing and thinner panels go in hand with thinner braces. 25 seconds of thinking plus real speaker building familiarity indicate the proper relation between bracing and panel thickness is more nuanced than indicated.

JBL adjusts the amount of bracing this way: "Proper bracing ..., depending on the size of the box panels." (note 1 P. 4, note 3 P. 2) Therefore according to box size. Electro-Voice is no different but interestingly indicates from what point one needs to do MORE: "In the largest boxes - greater than about six cubic feet- extra internal bracing is usually required for the largest expanses of wood in order to prevent sympathetic vibrations from affecting overall system performance." (same EV doc. P. 8) Vibrations mean that "... wall vibration indicates that energy is being wasted to move enclosure panels rather than moving air."(note 2 P. 5). And both E-V and JBL recommend a front to back panels brace in large boxes (same EV doc. P. 8, JBL note 1, P. 4).

Also, the relation can be the following too. Other things being equal (e.g. wood type, box size, LF/levels involved) thinner panels are more vibration prone than thicker ones, therefore should require more extensive bracing to avoid resonance. Panel thickness/density and bracing being complementary towards rigidity. Less on one would require more on the other to get adequate stiffness. Meaning, If one uses somewhat thinner or lesser density panels on a box, then he/she must be prepared to do a more extensive job on the bracing needed to achieve acoustical deadness. This tells In cases the relation can be inversely related instead of a direct one.

More extensive bracing can compensate for less dense (or somewhat thinner) material: after stating that "particle board is the most cost-effective material for general enclosure construction", and that "Birch plywood is very expensive", JBL indicates an alternative: "... a carefully braced enclosure made of high grade void-free Fir plywood can do the job just as well in most cases." (note 2, P.5)

Therefore, panel thickness/density and bracing size and/or extent of it all work together towards the same goal of a rigid enclosure, plus will vary according to the situation: material type, density/thickness, box size, LF/levels to be reproduced.

Large box weight control at the expense of rigidity and acoustical deadness? Interesting question as I have 5 lengths of 1X3" softwood in stock (not for bracing). 4 of them recent from big box store and 1 older one. Measurements reality follows.

Recent ones are "Select" and have 2 3/8" W X 5/8+" thick (+ = about 1/32" more than 5/8", the former being the precision limit of my Craftsman US made measuring tape). As for the older length, same width, but on thickness add 1/32"+ to the above. Sure looks like skinny bracing in the present context of box size, driver used and VLF/levels involved, whether laying flat or placed on edge. Moreover, pine named in the plans is among the softest of woods.

As thin and soft as they are, 1X3" on edge (preferred method for rigidity) it would be difficult to screw these in place for strength with regular size screws, in addition to glueing them. Screwing them from outside the box they would probably still crack with # 8 or 10 wood screws (# 6 having low pulling force), not even sure drilling a small pilot hole would avoid brace cracking here.

3/4"+ strips of more rigid material (good plywood or particle board) of 3" width glued and screwed would do a better stiffening job than soft pine, flat or preferably on edge, without adding a lot of weight, if that is a real concern. In the present situation, being cheap on bracing is certainly not the proper way to go.

JBL's own trilogy of speaker builder papers mentioned below offer guidelines that sure don't support the cause of small bracing when mentioning 2x4" or 3" strips of Birch plywood on edge (not laying flat) (note 1 P. 2, note 3 P. 2, ). As for the supporters of 1X3", JBL indicates " 1X3" pine bracing fixed on edge with glue and screws to the enclosure walls will help provide the minimum necessary stiffening... If you are building large subwoofer enclosures, bracing with two-by-fours works better...". (note 2 P. 5)

New lumber dimensions have a tendency to "shrink" over the years: actual measurements VS nominal given as lumber mills repeatedly reduce dimensions a bit over time for profit and/or resources conservation. Like many others, 1X3" are progressively getting further away from their nominal sizes...

-----------------------------------------------------------------------------------------------------------------------------------

The rectangular cabinet's longest dimensions are on the floor/on top instead of standing upright like some others, and use one of the two smaller panels to house the woofer and vent, the other one being used for the input terminal connector. So a very deep but low profile cabinet occupying about 9 sq. ft. The large 15.5 cu.ft. exterior box used this way minimizes its appearance in a room (less obtrusive look) and preserves more sight lines, while looking also like a "table".

Compared to the other boxes in the article, this one uses a different configuration, or makes use of the box shape differently. Though no specific explanations were given for this choice (other than enclosure proportions of the 8 cu.ft. being equally suited to lowboy or highboy orientation on p. 6), one can figure out that required vent lenghts of 20" (Fb 25hz) or 30" (Fb 20hz) dictated the cabinet's configuration. Had the same cabinet been used as a conventional upright box with woofer on largest panel, the present 21" height becoming 21" depth, would not have accomodated these vent lengths properly.

As seen in the Kramer/Timbers article and in the post # 26 plans, the vent is pretty close to the woofer (about 6mm). This appears to be less for reasons of large vents having less disturbances in close proximity to woofer, mentioned before, than as a result of closeness dictated by evident box configuration to accomodate vent lengths. Vent placement/proximity to panels/braces in the box seems unconventional compared to some guidelines, however with the box configuration adopted and vent diameter/lengths, the port is pretty much destined to be located where it is in order to try to clear bracing shown.

More to come.

Richard

P.S. RE posts # 105/107 Large cardboard tubes for concrete footings, to be used as very large speaker vent. Went to Home Depot recently and at the same time had a quick look at these tubes, as I said I would in post 107. The nominal 8" dia. has 7 5/8" internal and material thickness of 3-4 mm (1/8+"). I squeezed the tube a little to assess its rigidity, I'd say its "average". May need a touch of "doctoring" to add some rigidity to it, in order to keep it as dead as possible, specially as length increases. To reduce risk of resonance at high power, wrapping the outside of the tube with overlapping layers of "thick" rubber tape might do the trick since rubber is a pretty dead material.

Note 1: JBL, Vented Loudspeaker Enclosure Construction and Operation.
Note 2: JBL, The Most Commonly Asked Questions About Building Enclosures.
Note 3: JBL Pro, Enclosure Guide.

Ian Mackenzie

08-22-2018, 03:12 PM

I posted this link originally in a thread concerning the Mechanical X max in relation to X max of an LE14.

The discussion took on a review of Jbl published TL parameters by RMC who concluded the 2234H and the 2335H have identical Xmax and would therefore have the same Mech X max.

http://www.audioheritage.org/vbulletin/showthread.php?40955-LE14h-3&p=416617&viewfull=1#post416617
http://www.audioheritage.org/vbulletin/showthread.php?40955-LE14h-3&p=416530&viewfull=1#post416530
http://www.audioheritage.org/vbulletin/showthread.php?40955-LE14h-3&p=416604&viewfull=1#post416604
http://www.audioheritage.org/vbulletin/showthread.php?40955-LE14h-3&p=416617&viewfull=1#post416617
RE: "The mass control ring may limit excursion." (Post # 11)

According to Giskard's table in post # 9, the 2234H "(2235H with mass ring removed)" has the SAME Xmax and Xmech numbers as the 2235H, so the mass ring doesn't appear to be part of the explanation here. Regards,

Richard

http://www.audioheritage.org/vbulletin/showthread.php?40955-LE14h-3&p=416638&viewfull=1#post416638
http://www.audioheritage.org/vbulletin/showthread.php?40955-LE14h-3&p=416639&viewfull=1#post416639

While RMC’s intentions may have been well reasoned the reality is the infamous mass control ring mounted in the 2235H vc limits the Mech Xmax. See comments below by 4313B who had direct access to behind the scenes insights of JBL transducers.

I found this post with Google quite easily.

Without raising the usual rhetorical response from RMC the penny drops that you simply can’t go by papers or published data to demonstrate and prove that you above everyone else are right in what you “might” think you know.

There is no substitute for a thorough background knowledge of these drivers and systems in production and how the perform under various applications in the market place. The information, insights, product and people profiles in the Library is also a great place to gain a real understanding of JBL transducers and systems. It takes years to gain this level of understanding and familiarity. The reference area has numerous technical documents on the transducers and systems. Also refer to Don’s Stereo Sound Article (see stick under General Forums). This is the history and Legacy of JBL.

http://www.audioheritage.org/vbullet...p/t-20681.html

4313B
04-08-2008, 04:38 AM
A 2235H used as a sub can easily be overdriven and destroyed.
?????The mass controlling ring as used in the 2235H has fallen out of favor due to the limiting of xMax (This doesn't mean that people with a B380 and BX63 or BX63A should immediately start modifying that particular system design). Current thought is that the 2234H along with a few dB of EQ to fill in the resulting loss of VLF extension is a better solution. The Velodyne SMS-1 Mr. Widget recommends fills the bill. However, the Velodyne SMS-1 probably warrants a more modern transducer design such as the 1500 SUB or W1500H as Mr. Widget also states. Both of these transducers are significantly more robust and designed to handle the stress of small sealed enclosures. They are designed to handle EQ on the bottom end. Very small sealed box plus EQ. JBL has also used them in slightly larger vented boxes as well.

If one doesn't have the kind of funds required to run these modern subs one can go with something like the W15GTi mentioned by toddalin above. This driver has a higher Q and shouldn't require any EQ. It will dump a ton of bass tones into a room. It is specifically designed to sweep the field of competition in automotive applications but everyone is allowed to use any transducer any way they want regardless of design or intended application.

Anyone else slapping around the mass rings and if so on what DVD's??Quite common and it started when CD's hit the market. It was a source of warranty repair.
With both 4344 in 5 cubic ftDoesn't really count.
and now a B380 I have yet to ring the bell using 2235's.Shouldn't happen very often in the B380 with the BX63 due to the bump filter.

I have been able to get 121A to clank but only in a sealed box at high SPL levels.A 20 Hz filter should take care of that. They took a real beating when CD's first came out.

RMC

08-22-2018, 09:18 PM

What's his real objective here? Looking for a tribune? He could easily start his own thread with that but has decided not to... Stirr up controversy?

Transporting the issue from "Product General Information" "LE14H-3" thread into "Product DIY Forum" "DEEPER BASS: D. B. KEELE/E-V'S STEP-DOWN MODE", something belonging to the former, into the latter appears pretty curious in terms of intent and relevance.

The "Deeper bass ..." thread is evidently about LF assisted alignments boxes, B6 or so. It has nothing to do with the mass ring issue. One can only wonder on real motive.

"The discussion took on a review of Jbl published TL parameters by RMC..." Purely a mirage as I've reviewed my few posts and this simply doesn't exist in LE14H-3 thread...

My only contribution to that mass ring issue is the following mention in post # 15 of that thread:

"Hi Olaf,

RE: "The mass control ring may limit excursion." (Post # 11)

According to Giskard's table in post # 9, the 2234H "(2235H with mass ring removed)" has the SAME Xmax and Xmech numbers as the 2235H, so the mass ring doesn't appear to be part of the explanation here. Regards,

Richard"

RE: "... you above everyone else are right in what you “might” think you know." Do the above underlines in my very short post reflect that??? Another mirage. I wonder who the usual rhetoric really belongs to...

He subsequently, in post # 17 of that thread, posted the text from 4343B, on which I never even commented, and re-posts it again here today for the gallery i guess, since where's my issue on that???

Using this thread as an opportunist just to try to stirr up an argument that simply doesn't exists! He'll debate that mass ring issue with himself as far as I'm concerned.

Ian Mackenzie

08-24-2018, 10:35 PM

It appears your only experience/exposure/understanding with JBL is to post regurgitating text references you have read on this or other audio forums or old AES papers, condescending emoticons, and quoting people like D.B Keele endlessly.

You have publicity bagged Greg Timbers , many others and it would seem anyone you don’t agree with or understand.
That includes the sub woofer article, criticism of jbls TL data. The irony of this is you clear are always right but don’t have any understanding of the subjects being discussed . Instead you plagiarise, mis quote and remove the context of other members well intended response. Any idiot can play that game.

Is that a nice person? Unlikey.

Which by my interpretation means your understanding of JBL ends with an online bass reflex simulator program and uneducated guesses. >Go spend a month reading the JBL Library and stop giving people the shits. You might then be better placed to enter forum discussions and make a positive contribution.

Back on post 63 l quoted with Permission from DB Keele and the LH Administrator a response to my email for an explanation of the Step down paper by Keele.

The quote is below.

RMC responded with a scathing personal attack against me! Why? We’re not sure? Narcissistic disorder? Who knows. We think he just has to be right every time.

I still have the option to litigate on the matter. Up until now l have not been concerned. The problem is he probably isn’t worth 2 cents.

It will be interesting to see RMC response on what is the most informative post in this entire thread.

From post 63.
For or those interested in this topic l contacted the author of the paper below requesting clarity on the EV step down implementation.

The author kindly responded with the explanation below.

There are 3 steps:

Step 1
You just tune your vented box with two identical ports which tunes the box to a conventional 4th-order HP Butterworth alignment.

Step 2
You then cover one of the ports which drops box tuning down about one-half octave ( x 0.707 fB).

Step 3
You then EQ the response with a second-order HP filter with a Q of 2 (boost of +6 dB) at the lowered resonance. This changes the tuning to a 6th-order HP with the lowered f3 about one-half octave below the original fB.
The paper explains all this. See Figs. 2, 3, and 4.