JBL 2235 with 2450SL and 2332 horn?

[dubkarma]

I'm wondering if the 2234 or 2235 woofer would be a good match, in a compact (5 cu. ft.) two-way system, for the 2450SL compression driver and 2332 horn?

I had originally thought to find some 1400nd or 1401nd drivers, a la DMS-1, but haven't come across anything but recone kits.

Just concerned that crossing over the 2235 at 1 kHz—the crossover frequency used in the DMS-1—is asking a bass driver to play too much into the lower mid-range. . .

Would appreciate any tips or advice on this matter. . .

[grumpy]

4430/5 series achieves this fairly well.

[dubkarma]

4430/5 series achieves this fairly well.

Good to know! Thanks for pointing that out. Shall forge ahead. . .

[sebackman]

Hi,

You should be fine with a 4" (2447, 2450SL, 2451, 2452 or 2453) 1,5" driver with SL diaphragms. No real need for UHF with those diaphragms just some tweaking in the DSP. The 243* drivers do not seem to work equally good on the M2 WG

However, M2 is a system with the specific BSS DSP, the JBL settings, the cabinet and the specific drivers. If you alter any of this it is no longer an M2 system and the result will be different.

You may very well like the new system and be very happy with it, but an M2 it is not.

I have tried many drivers on the M2 waveguide (I got my first pair of M2 WG’s in early 2015) and my preference is the 24XX-sl drivers on a stand-alone basis. The Be drivers may sound a little “closer” but the early drop off in frequency and IMHO need for UHF support makes the SL a better choice. However, if you add the JBL M2 factory settings D2 is a better/easier choice unless you spend a lot of time on measuring and testing.

Us mere mortals cannot expect to achieve the same level of system quality as achieved by JBL with thousands of hours work going into the M2 system.

If you have the 4” drivers go with them but expect to put in many measuring hours to get them working. If you need to buy drivers get the D2’s and be done with it.

Having said all that, I build a pair 2-ways with with LE1400H woofers, M2 WG’s with 2450SL cores (476Nd diaphragms), BSS DSP with tweaked JBL M2 settings and they sound wonderful.

I’m also building a system with 2451Be (Truextent) on M2 WG’s and as Iveca said due to them falling off early I’m going to use 045 UHF drivers with them. They will definitely not be M2 clones but have a potential to sound pretty decent.

You choose, easy way with predictable very good outcome = build faithful M2 clones with BSS DSP. Or go you own way and expect quite some man hours and with the possibility to get very good result.

Kind regards
//Rob



Hi,

If you want to cross over that high the 2235 may not be the first choice (2332-2334 should not be used below 1khz) . I budget permits look at the new 2216 driver. If not see if you can find a L14H-2 or 3, they would do a better job at it. DMS1 was dual LE1400Nd’s.

There are several other JBL woofers that would be good choices. And many very experienced people here can surely come with suggestions.

2235 is a dedicated woofer with a heavy cone and as such would benefit from XO lower than 1KhZ. I built a monitor years ago and used a 2118 8” from 350Hz.

If you do decide to go the 2235 route I would recommend to remove the weight ring under the dust cover to turn it into a 2234 that works better for mid.

And while I’m at it you may want to look at a newer horn/waveguide. The 2332 was a good horn back when but today the technology has moved on to waveguides and the difference is rather big. The “horn sound” is gone and it sound more like a big dome but with the clarity and dynamics retained. However, many prefer the vintage sound and I have great respect for that so only you and your ears can decide.

If an option for you, I would suggest to take a look at the VTX F12/F15 (STX825) waveguide. Looks el-cheapo plastic but is in reality very good and really out-guns all of the older designs except maybe M2 for HiFi use IMHO. It also measures very good.

There is lots written here on LH in other threads.

Kind regards
//Rob

[dubkarma]

Thank you, gentlemen, for the additional comments and information. As it happens, I do have a pair of the STX825 horns. I got them for the D2430K drivers I sourced a couple of years back. Unfortunately, in tests I had done by an experienced speaker designer, they had less HF output than any compression driver I've ever heard. Given all the press and positive discussion about the D2430K, I remain completely baffled by this. Took them to a JBL Service Centre here and the guy told me they were working fine. More bafflement, but for now they're resting quietly in a box in the closet.

I suppose I could mount the 2450SLs on those little plastic STX825 horns if I built some sort of cradle inside the cabinet to take the weight of the driver. And I do have the option of reconing my 2225 drivers with 2235 cone kits and leaving out the mass rings. I also have the option of using TAD TL-1601b instead of 2234/2235s. But not in a position right now to acquire 2216 or other woofers.... Or maybe best to postpone the project until I can afford more suitable woofers such as the 2216. . . Then there's the crossover, but that's a whole other story. I'll probably use my old DriveRack 4820 at least to get things going. . .

[Earl K]

Thank you, gentlemen, for the additional comments and information. As it happens, I do have a pair of the STX825 horns. I got them for the D2430K drivers I sourced a couple of years back. Unfortunately, in tests I had done by an experienced speaker designer, they had less HF output than any compression driver I've ever heard. Given all the press and positive discussion about the D2430K, I remain completely baffled by this. Took them to a JBL Service Centre here and the guy told me they were working fine. More bafflement, but for now they're resting quietly in a box in the closet.

I suppose I could mount the 2450SLs on those little plastic STX825 horns if I built some sort of cradle inside the cabinet to take the weight of the driver. And I do have the option of reconing my 2225 drivers with 2235 cone kits and leaving out the mass rings. I also have the option of using TAD TL-1601b instead of 2234/2235s. But not in a position right now to acquire 2216 or other woofers.... Or maybe best to postpone the project until I can afford more suitable woofers such as the 2216. . . Then there's the crossover, but that's a whole other story. I'll probably use my old DriveRack 4820 at least to get things going. . .

If you bought those D2430K(s) used ( via eBay for instance ), the explanation of their poor performance might be more easily explained.

You wouldn't be the first to be burned this way.

:)

[dubkarma]

Earl, Yes, indeed, I bought them used on eBay, and that, I guess, serves me right! Yet the fellow who's been repairing and reconing speakers (JBLs and TADs) for me for many years can find no malfunction. That's what baffles me.

[Earl K]

How do the curves of your drivers compare to those found in this linked thread? (http://www.audioheritage.org/vbulletin/showthread.php?38697-Measuring-data-for-D2-(2430k)-on-M2-waveguide-wanted&p=396521&highlight=D2430K#post396521)

For example;

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=73018&d=1470779794

:)

[dubkarma]

HI again, Earl. I don't have any response curves for the D2430K drivers. I don't think they were tested to that extent. Just got a verbal report that they were functioning normally. Though I also got a report from a different tester that, whether configured as 8 ohms or 32 ohms, the drivers, on the STX825 horn, roll off even more rapidly than the older JBL large format drivers, such as the 2445J. Curiously, I was also told to use a four-conductor speaker cable to connect the negative side of the cable to both negative terminals and the positive side to both positive terminals. Which is not how the drivers came to me with that yellow jumper cable between one positive and one negative terminal. In any case, that's why I have abandoned the D2430K and have decided to go with the older 2450SL. . .

[sebackman]

Hi dubkarma,

I have no idea who tested the 2430k drivers for you but they are either both faulty or the measurement is wrong. I have done many measurement of many drivers on that horn and there is no problem with the D2's. All drivers will experience a fall off in frequency from about 2-4kHz with about 3-6 db per octave on a CD horn/waveguide , that is normal. So, you will need some type of correction circuit, either passive or active. However, that is not specific to the D2's and it sounds like you get good result on the same waveguide with other drivers.

The info that older drivers have less of a roll off seem to be completely wrong as the 2445/46 are a 2" driver and the STX horn is designed for 1,5" drivers. None of the 2" drivers have the same HF extension as the 1,5 drivers.

On the D2, they should not be configured in any other setup than the two voice coils in series. I think someone screwed up the connection on your drivers. There should be a short lead between the upper (exit facing up) voice coil negative (lower connector) to the lower voice coil positive (upper connector, ie no 3 from to with exit facing upwards). There should be only two leads connected going to the driver with the positive lead going to positive connector on the upper coil and negative connection to the negative connector of the lower coil. Disregard all other info on connections.

Unless the have been subjected to moisture which can destroy any driver I see no reason why both should behave in the same way. I would check the measurement again and make certain that the short connector between the 2 diaphragms are correctly mounted to rule out any phasing problem.

Does both voice coils give on both drivers (4 in total) give correct ohm reading?

The STX horn is quite sturdy so there is no need for extra support unless you are going on the road. I have made many cabinets with that combination and none has failed so far.


Kind regards
//Rob

[dubkarma]

Will attempt to compare the 2450SL + 2332 horn with the D2430K + STX (#5006812) horn with dual JBL 2235H per channel in 8 cu.ft. boxes tuned to around 30 Hz. Which plan leads to more questions. . .

1. What length bolts are people using to mount the D2430K to the STX horn? 1.25" seem to be too short and 1.5" too long. As you can see, in terms of DIY skills, I stand at a very primitive level.

2. Can one cross over the STX horn as low as 1 kHz? Or even lower? I'm guessing not, based on nothing more than its size. And the fact that JBL uses a 1.3 kHz crossover frequency in the STX825 speaker system, but I don't know what slope is used. If 1.3 kHz is the lowest recommended frequency for crossing over the STX825 horn, the 2235H are definitely not a good match and one would have to introduce a mid-range driver (e.g., 2118, 2123, etc.) or, to remain a two-way design, some other kind of woofer. Prefer to stay two-way and keep the VLF performance of the 2235s.

3. Given that my dual 2235H are in smaller than optimum cabinets (8 rather than 10 cf), so far, using the JBL M553 with its built-in EQ for CD horns to cross over at 1 kHz (fixed 24 dB/oct. L-R slopes) to the 2450SL/2332 yields pretty good results. And that's even before setting up the mike and starting objective measurements and associated tweaking. It's quite possible, for example, that 24 dB L-R are not the right topology to use.

4. For this reason, it would be useful to know whether there are any "presets", perhaps taken from the DMS-1 active system, that could be programmed into the DriveRack 4800 to optimize at least the HF section that uses the 2450SL/2332? I believe I've had enough practice with the dual 2235s that I could, with local help, handle the low-pass section.

5. Which leads (somehow) to a question about using dual woofers per channel. JBL recommends putting two 2235H per channel into a 10 cf cabinet subdivided into two independent 5 cf sub-enclosures, each tuned to 30 Hz. On the other hand, in other of the company's designs (admittedly mostly for PA work), two identical drivers (e.g., 2226H) are placed in one large box without internal dividers. And when George Augspurger designed a pair of speakers for me, he also specified using dual TAD TL-1601bs in a single 12 cf enclosure. . . So what's the current reigning philosophy on enclosures for dual woofers?

Many thanks, guys, for so freely sharing your experience and expertise!

[dubkarma]

So far, the 2450SL on the 2332 horn gives a more spacious, relaxed presentation (there's some precise engineering terms!) than the D2430K on the STX825 horn. Both crossed over @ 1 kHz with a 24 dB/oct. Linkwitz-Riley slope using the JBL M553 crossover with the CD horn equalization engaged—which is all I have on hand right now.

Perhaps the D2 + STX825 horn doesn't need the –4 dB @ 2 kHz and +6 dB @ 20 kHz that this EQ circuit imposes and trying them without will be necessary. Certainly the 2450SL/2332 benefit from it.

Anyway, shall go ahead and build 5 cf cabinets for the JBL 2234H with 2450SL/2332. And after that for the D2 driver/STX825 horn with the JBL 2216nd-1 LF driver. I anticipate spending much time thereafter getting the crossovers right, probably using the DriveRack 4800 that I've just had refurbished. . .will endeavor to post measurements using the REW calibrated mike and software to which I've recently been introduced. Thanks again, gentlemen, for your many helpful comments!

[ivica]

So far, the 2450SL on the 2332 horn gives a more spacious, relaxed presentation (there's some precise engineering terms!) than the D2430K on the STX825 horn. Both crossed over @ 1 kHz with a 24 dB/oct. Linkwitz-Riley slope using the JBL M553 crossover with the CD horn equalization engaged—which is all I have on hand right now.

Perhaps the D2 + STX825 horn doesn't need the –4 dB @ 2 kHz and +6 dB @ 20 kHz that this EQ circuit imposes and trying them without will be necessary. Certainly the 2450SL/2332 benefit from it.

Anyway, shall go ahead and build 5 cf cabinets for the JBL 2234H with 2450SL/2332. And after that for the D2 driver/STX825 horn with the JBL 2216nd-1 LF driver. I anticipate spending much time thereafter getting the crossovers right, probably using the DriveRack 4800 that I've just had refurbished. . .will endeavor to post measurements using the REW calibrated mike and software to which I've recently been introduced. Thanks again, gentlemen, for your many helpful comments!

Hi,

It has been shown that some improvements can be get using Jbl 2452 and STX825 by applying 0.5 inch "spacer" between them. A kind of notch in the response can be almost eliminated.....so may be with 2450-1.5 the same results can be get if necessary.

regards
ivica

[dubkarma]

ivica, Thanks for the suggestion. However, I'm not using the 2450SL with the STX825 horn; that's for the D2430K. With the 2450SL, I'm using the 2332, which I understand is the same horn and driver pairing (except for the ribbed diaphragm) used in the DMS-1.

[Dave M]

Hi,

It has been shown that some improvements can be get using Jbl 2452 and STX825 by applying 0.5 inch "spacer" between them. A kind of notch in the response can be almost eliminated.....so may be with 2450-1.5 the same results can be get if necessary.

regards
ivica

Where I can find this report? I could only find opposite report adding a spacer...

http://www.audioheritage.org/vbulletin/showthread.php?36686-New-JBL-waveguides-5006812-90x50-vs-PT-F95HF/page4

In my adapter drawing the thickness of the adapter is alittle less that 1mm which seem to work fine. Originally I had a thicker platebut that was not as good when measured with 2451/475Nd drivers. A 6-10mmdistance was clearly measurable as an un-even curve.

[1audiohack]

Like this?

Barry.

[RMC]

I certainly don't intend to de-rail the thread but I do note no one has answered here since the last picture was posted days ago...

I'm of the opinion that slot side wall vents give a low-frequency cabinet better appearance than tube ones as shown here. I'm mostly interested by the very good looking LF enclosure having narrow vertical side wall vents on the baffle. They seem convenient to make efficient use of front panel space available. They also tend to minimize the perceived appearance of vent size (less gross) VS the big hole(s) in the box...

I see these vents from time to time on commercial and DIY cabinets. For example, the small Genelec studio monitors 1030A (6.5", 80W) and 1032B (10", 180W) both have slot vent on each side of tweeter, not wall sided though, and their look isn't as nice as here in my view. Plus those small speakers are not as large air movers as the woofers in the post.

I estimate the vents seen on post # 16 to be about 1" wide and 15" high, so about 15 sq.in. each, or the equivalent of a 4.4" diameter port. Not far from JBL's minimum recommended for a 15" driver (i.e. one-third of the 15" woofer's diameter). Also power input related. Their latest advice is to use the largest port area that will practically fit in the box, makes sense with the ever increasing output of more modern woofers.

As a form of rectangular vent, slot ones are ok in principle. Vent shapes like square, rectangle, round or triangle usually don't present a problem. However, narrow ones seen on some enclosures have been a question mark in my mind for a while, certainly not regarding the nice look they give to a box!

I've always wondered about their good or less so? acoustical performance, more so when the narrow slot includes one or two cabinet walls. That concern I've had about them is probably why I never dared using such. Prudence has made me keep vents away from walls as often as I could. They could work as well as others or not, I wasn't sure about this.

In normal home use sound levels these may not present an issue at all, but what happens as power goes up markedly? In the example seen two relatively high power VLF drivers are used, possibly in parallel, and these drivers can move a sizeable amount of air. Will that port's width cope adequately with the large air flow? Is the vent located to avoid turbulence or are slots prone to port noise or whistling at high level?

Since I haven't used such ports up to now, I looked into my speaker building stuff to see what JBL and others had to say about such vents. As expected, location of a vent is GENERALLY not critical, but some manufacturers seem to have a preference.

Fane Acoustics (note 1) says ports should be located near the drivers, and between these when multiples are used. Based on their image shown a slot vent would be horizontally oriented and located between both woofers (in the present case it would be impossible re cab baffle size). In E-V's doc, there's no mention about vent location, however out of five box plans with double woofers, four of them have the vent(s) somehow placed between the woofers (note 2). On JBL's HLA Series 4897/A, very high output LF cabs the large aerodynamic vent is also placed between the two woofers.

Fortunately, JBL provides a little more insight with regards to vents including 1-2 walls. After stating that if required "insulation should be removed from the immediate vicinity of the port end", it goes on to say that "... as long as extreme length-to-width ratios are avoided." What is an extreme ratio? No say. I have not modeled scenarios to try to get an idea. Though making such vents much wider (height shorter or length longer to keep Fb) would reduce their good looks and efficient use of space, though improving their ratio.

JBL adds " One or two sides of the box may be used as sides of such a port, but this will cause an alteration in the expected tuning. Common wall ducts should therefore be designed to allow for some length adjustment after the box is completed." (note 3)

Also, the presence of an unobstructed air path between the driver and the vent is mentioned. In practice, this would depend on how deep such a vent goes inside the box, as well as how high a vertical slot vent is. On the issue of where to locate the port, JBL says "Overall, it's safest to locate the port somewhere on the baffle with the woofer(s), far enough away from side walls to avoid interaction between port and enclosure wall or the fiberglass insulation on the wall." (note 4)

"safest" doesn't mean slots are plain bad or must be avoided, but rather more like can be used with an eye kept on common wall interaction/tuning aspects, length-to-width ratio, distance and air path with driver.

Each box designer (DIY or Pro) makes his own choices/decisions and has his reasons for doing things a certain way. These are most often as good as anyone else's, whether it be budget, space/box size, material available, complexity, look, sound perceived, etc.

Richard

Note 1: Fane Acoustics, Loudspeaker Enclosure Design And Construction, P.5 ( Now called Fane International, Acoustics is now their Musical Instruments Speaker Division)

Note 2: E-V, Pro Sound facts, No. 7, P. 16-18

Note 3: JBL, Vented Loudspeaker Enclosure Construction And Operation, P. 3

Note 4: JBL, The Most Commonly Asked Questions About Building Enclosures, P. 3, 4

[Dr.db]

Have you compared your JBL 2234 with your TAD 1601 yet?
I´m wondering which woofer sounds better to your 1khz crossover?

[mortron]

In regards to the dual woofers... Have you considered trying them on their sides a la the 4350 and your TAD monitors? Maybe there is something to horizontal vs vertical configuration. Then both woofers are equidistant from the floor. May get too much reinforcement from that, but maybe the ticket.

[1audiohack]

Hello Richard;

Esthetically I like slots.

In air flow round is king and a slot with a high aspect ratio is the poorest choice.

Over a decade ago I did a ton of modeling in LinearX Encloseure Shop and found that if you stick to what I found is a thumb rule (at least for me) that is driver Sd times Xmax for port area, depending on aspect ratio and port location you can move things around several Hz is about all. I did a six box experiment on very different port placments and shapes to verify the models were correct and called it good.

On slots I err just a tic big on area since they don’t flow as well but have yet to “hear” them. I should do a port compression test on round vz slot sometime.

As far as front or rear it seems like nearly all of JBL’s speakers designed for domestic use have the ports on the rear to minimize midband radiation I assume. Virtually all the pro boxes including real (large format) studio monitors are ported out the front.

All the best.
Barry.

[RMC]

Hi Barry,

Thanks for the input on slot vents.

The LF cabinet shown not only has great looks, but with the slot type vents its a definite homerun, for appearance and efficient use of space available.

I don't know if round vents are always King. They probably are in terms of number of uses for practical reasons (easy to find and install, many dimensions, low cost, etc.).

All vent shapes considered, THE King for air flow performance could be the huge type of vent on JBL's HLA 4897 and 4897A. Its not round, though it has rounded corners, and could also be perceived as a large slot with flared ends... Developed through extensive aerodynamic studies of air velocities for extreme LF outputs.

With regards to vent shape (round, rectangular, square or triangular) I don't recall seeing info naming one type better than others for general use (as long as vent proportions are acceptable). Round flared ones have their fans, having some merit concept wise, but their execution details/specs are often unknown, and possibly plagued with some issues that are not necessarily known to all (note 1).

The use of Vd (Sd x Xmax) plus a little margin for port area is clever. When that does the trick, great then.

Both Small (1973) and Engebretson (1984) use the Vd number, as well as Fb, in their equations to determine vent dia. The latter's results however are usually larger dia. than the former's, which in practice makes sense being 11 years more recent, and considering there were already some higher power drivers with increased LF output capability in 1984 (e.g. 2245H). Today with 2 KW or so drivers the vent diameters should increase even more.

Regards,

Richard

Note 1: A. Salvatti, A. Devantier and D. J. Button, Maximizing Performance from Loudspeaker Ports, JAES, Vol. 50, No. 1/2, Jan./Feb. 2002, P. 19-45.