Horn Recomendations for 1.5" Drivers [Archive]

Robh3606

08-24-2006, 02:08 PM

I quess what like to do is get my hands on a pair of Array horns! Wishful thinking!!

Thanks Zilch on the links I will have to go through them.

Hey Widget

No I am talking 3 way no tweeter. My active set-up has 2435's with no tweeter and it's fine for me at least. One of these days I should give one a try though just to check it out. I have heard the Edgar Horn Tractixs and that's not what I am going for. So far with the PTH the only issue I see is the low end loading. They measure well and subjectively sound fine as far as their upper extension goes. You have to remember I like the 2344 and was fine with a little off the top and switched the 2435 in as a replacement. This horn and driver combo are actually a bit better up top and sounds more natural to boot.

Rob:)

mikebake

08-24-2006, 02:11 PM

I have heard the Edgar Horn Tractixs and that's not what I am going for.

Rob:)
Why not?

Robh3606

08-24-2006, 03:17 PM

Hello Mike

No slight I really liked them but when I was at the demo it seemed they had defined sweet spot. I like it a little less defined and wider with smooth power response, in the room.. I guess I am used to the 2344 and like that. That seems to work better for me in my listening room. I like an open sound and don't like hearing things change if I shift in my seat. I also don't always listen on axis and the balance doesn't change all that much off axis, at least not like the 4344 which is much more directional with much tighter control. It's one of those things. The new 100x100 PT waveguides share this with the 2344. It a personal preference is all. I have every thing toed in as it is anyway so in the chair it doesn't matter. Hey my impressions are from the MAF. You guys who have them at home, what's the deal?? Am I FOS on this or what?? What do you guys get in your living-rooms???

Rob:)

Mr. Widget

08-24-2006, 03:23 PM

I quess what like to do is get my hands on a pair of Array horns! Wishful thinking!!Have you heard them? I would need to hear them for myself before I got too excited about them... don't get me wrong, I am thrilled that JBL has produced them and is paying attention to this market segment, but all that aside, without actually hearing them, I'd keep them in the maybe category.

This horn and driver combo are actually a bit better up top and sounds more natural to boot.Play Steely Dan Katy Lied and listen to the cymbals and the chimes on your system in your avatar and then listen to the 2435... and tell me the highs sound good.

Why not?Ditto!

Edit... saw your post to Mike...

Widget

Robh3606

08-24-2006, 05:02 PM

Hello Widget

Have you heard them?

No and with their distribution system I probably won't. Since GT uses them at home in his system, based on his other work, that's enough of an endorsement for me. I would take the risk on that one. :D

Play Steely Dan Katy Lied and listen to the cymbals and the chimes on your system in your avatar and then listen to the 2435... and tell me the highs sound good.

Either the 2344 or the top end on the 4344's can't match the XPL's. That's a given. That is also why I keep 2 separate set-ups and a couple of speaker pairs up and running. I enjoy listening to them. No single pair can do it all and the 4344's I have up now do the chimes better than the 2435 PTH1010 set up just like they did with the 2425/2344's. It's not just about one strength or weakness it's the whole deal that matters. There are other aspects of the 2435/1010 combo I like quite a bit. As far as adding a tweeter maybe but right now that is not in the cards. I wouldn't argue your point about 800 vs. 18K. We all know there are issues above 10K with these drivers.

Ditto!

As I explained to Mike.

Rob:)

Ian Mackenzie

08-24-2006, 06:33 PM

Rob,

If you could mate your driver to an adapter of the right proportions the 2397 might be very interesting.

Ian

Robh3606

08-24-2006, 07:06 PM

Hello Ian

Can a 2397 get down that low??? I figured they were a 1K-1.2k horn looking at measurements. I was thinking a 2108 as the mid but would rather run the 2435 lower and see what I get.

Rob:)

subwoof

08-24-2006, 07:17 PM

Back in the early 80's a local genesis clone band ( their sound man is a forum member ) used 4 of the 2397's crossed at 800 with the stock 2440 alum dia's. The trick was to add a baffle to the top+bottom to load them. They were splayed ( as if 140 wasn't enough ) and it was outstanding.

I think that's mentioned in one of the older horn tech manuals.

My small PA uses the 2450SL / 2332 array horns along with the 1400PRO and they sound great no matter the volume. There is just no substitute for large diaphrams.

sub

ps - I have (8) of the DDS 1.5-70 horns in storage.

Zilch

08-24-2006, 07:26 PM

P-Audio claims PH-316 is good down to 500 Hz.

http://www.paacoustic.com/Product_Detail.asp?CatalogID=0117&ProductID=PH-316

You're welcome to try them, but you'll hafta send my NL200t3 protos back. :p

Guido likes 'em w/2435HPL.

[Geez, they're makin' one poo pot of horns, now: http://www.paacoustic.com/Product_list.asp?CatalogID=0117]

norealtalent

08-24-2006, 08:21 PM

Rob, I've been running 2435's on Smith's with a Cannon Sound 1 1/2"-2" for 2 years. I've a-b'd them side by each with 2441's. 2435's are awesome on Smith's. So are the 2441's. IMO, a Smith can't be beat. When you mate a 2435 with the 1 1/2 -2, the resulting throat is VERY similar to that of the 2441. You're not that far away, maybe we can set up a weekend audition. I can bring several combos of Be's w/ 2397's for some measurement and critical listening. I'm sure you'll like the combo.:)

Zilch

08-24-2006, 09:31 PM

When you mate a 2435 with the 1 1/2 -2, the resulting throat is VERY similar to that of the 2441. You're not that far away....That certainly seems to be the case with the large-format neodymium 245x drivers. The 1.5" versions appear to be the 2" ones minus the throat, i.e., the driver exit at the phase plug is actually 1.5" in both cases. Details on what's up with that are in the Optimized Aperture white paper:

http://www.jblpro.com/pub/technote/tn_v1n21.pdf

Mr. Widget

08-24-2006, 11:47 PM

I've been running 2435's on Smith's with a Cannon Sound 1 1/2"-2" for 2 years... When you mate a 2435 with the 1 1/2 -2, the resulting throat is VERY similar to that of the 2441.Is this the adapter you are using? (The one in the photograph.)

Here is a drawing of the TAD 4002 driver. It is sold as a 1.5" version without adapter and as a 2" version with the adapter. If the adapter you are using mimics this exponential expansion, I imagine you are correct and it will very closely mimic a proper 2" driver being mounted on the horn.

Widget

Steve Gonzales

08-25-2006, 12:48 AM

[quote=Mr. Widget]" I imagine you are correct and it will very closely mimic a proper 2" driver being mounted on the horn."

Well...., what do you know? Who says you have No real talent ? :D

The advice about using a baffle on the 2397 is great. I just tested this and got a noticeable improvement in sound quality with my 2397/2441 combo. I don't have any measuring equipment, but the difference is not subtle at all.
I'd love to read an explanation of why this works.

BTW, didn't I read that the proper aspect ratio of the horn height to diaphragm dia. is .5 ? 2435/435Be. = 3", 2397 = 1.5" Is that correct?

Zilch

08-25-2006, 01:05 AM

Do yer Smiths have LIPS?

JBL recommends them:

http://www.jblpro.com/pub/obsolete/2397.pdf

"Vertical dispersion is largely dependent upon the baffling; with the recommended cylindrical baffle extending at least 76 cm (3 in) above and below the mouth, a nominal 60° vertical beamwidth is achieved."

The original Smith design paper is posted somewhere in these forums with design details.

Steve Gonzales

08-25-2006, 01:15 AM

Ya know, I used 6" of foam on top of mine. less like a reflective type baffle and more of a sound absorbing one. The bottom of the horns have the side by side L222/220's below them. Whatever is going on, it sure smoothed the sound out. I must have a reflection problem. Does the recommended baffle extension help the horn achieve 800hz, or does it matter? That's how I read subwoof's advice. I thought the horn would go down to 800hz regardless

norealtalent

08-25-2006, 03:47 AM

Is this the adapter you are using? (The one in the photograph.)

Here is a drawing of the TAD 4002 driver. It is sold as a 1.5" version without adapter and as a 2" version with the adapter. If the adapter you are using mimics this exponential expansion, I imagine you are correct and it will very closely mimic a proper 2" driver being mounted on the horn.

Widget

That certainly looks like a similar designed adapter. May very well be identical.

Mr. Widget

08-25-2006, 10:51 AM

Well...., what do you know? Who says you have No real talent ? :D
Even a stopped clock is correct twice a day.

Who said we don't have a sense of humor on this site? :bouncy:

Widget

Mr. Widget

08-25-2006, 10:52 AM

That certainly looks like a similar designed adapter. May very well be identical.My point was that if the expansion is continuous like it is on this TAD example then you will indeed be mimicking a traditional 2" driver. The 2328 and the 2397 "Smith" horn were designed to work with that type of driver. All of the traditional 2" drivers from JBL and TAD and others are based on the original geometry of the Western Electric 594 2" exit driver. These drivers have a throat that has a ~300Hz cutoff and the expansion of the throat is an exponential horn of that rate.

I don't think the initial expansion within the 243X series of drivers is of this rate so even applying an extension that is of the proper rate will exactly duplicate a 2" exit driver like this TAD example does, but the discontinuity may be slight enough that the results are quite acceptable.

You have compared the 2435 using your adapter with the 2441 and found it to be more than acceptable so I would assume you have lucked into an adapter with geometry that seems to suffice. I posted the photo of that adapter in an attempt to clarify which adapter you are using so that others may give it a shot and see if they have similar results. The photo I posted was from the Cannon Sound (Australia) website. I believe the adapter pictured is a P-Audio model. Could you tell us where you sourced your adapters and if there are any markings on them?
Thanks,

Widget

matsj

08-25-2006, 11:35 AM

Tractrix horn from : Stereo-Lab.de
425 Euro for a pair.

mats

Zilch

08-25-2006, 12:42 PM

P-Audio PC5038, perhaps?

No dimensioned drawing on the website:

http://www.paacoustic.com/pdf/ACCESSORIES/PC-ADAPTORS.pdf

grumpy

08-25-2006, 01:02 PM

Re WE594 and it's children:

"By our calculations, the initial flare rate in the older
driver design was approximately 160 Hz, reflecting the
need to drive the very large horns that were used in
early motion picture systems. Today, we can double or
quadruple that flare rate, inasmuch as many horns are
now intended for nominal crossover at 800 Hz."

:blah: So here's what I get out of it:

Pattern control appears to be the primary benefactor of increasing
the driver's flare rate, but the comparison of distortion levels, especially
between 2450/2380 and 2451/2352 combinations would seem to indicate
an additional benefit of the wide flare/Optimized Aperature horn pairing.

As good as the 2435/adapter/2397 may sound (indeed, one of the options I'm
considering myself), I can't help but think there may be some benefit in
using a much shorter/abrupt transition adapter (understanding that the smith
horn itself may be the limiting factor in pattern control in this instance).

I suppose the 2435/adapter/2397 may also just be one of those happy
circumstances, but it does seem as though some optimization for the
2435 might be in order (all already mentioned: flare rate matching, horn
scaling, etc...).

I'm certainly enjoying and interested in listening to all
of your experiences and ideas (so thanks for that). :applaud:

Cheers,

-grumpy

Mr. Widget

08-25-2006, 01:41 PM

Re WE594 and it's children:

"By our calculations, the initial flare rate in the older
driver design was approximately 160 Hz...I'm not sure if the 160Hz vs. 300Hz is a function of my fuzzy brain or if I was mixing up usable frequency vs. cut off frequency... as in our tractrix discussion earlier.

In any event, yes pattern control does seem to be much more of an issue in today's designs. I think it is primarily due to the fact that contemporary horn design is almost exclusively in the pro audio domain and most modern sound systems use arrays of speakers that need to work in concert (no pun intended) and not create the lobing and other problems stacking a pile of A-7s or vintage JBL's would create.

All that aside, what will sound best in a home environment is the issue at hand. I have a strong personal bias against the JBL Biradial horns. I have never heard any system using them that sounded as good in terms of imaging or smooth frequency response as a tractrix or some of the other horns including the trusty old exponential radial horns.

Widget

norealtalent

08-25-2006, 01:52 PM

You have compared the 2435 using your adapter with the 2441 and found it to be more than acceptable so I would assume you have lucked into an adapter with geometry that seems to suffice. I posted the photo of that adapter in an attempt to clarify which adapter you are using so that others may give it a shot and see if they have similar results. The photo I posted was from the Cannon Sound (Australia) website. I believe the adapter pictured is a P-Audio model. Could you tell us where you sourced your adapters and if there are any markings on them?
Thanks,

Widget

The adapters I use are from Cannon Sound, they look just like the picture but have no identifying marks. They stopped offering them for a while but I have been told they are available once again. The 2435 mounting holes must be drilled and I put them in the lathe to match the driver and adapter perfectly.
The 2435 uses a quite different expansion to the throat than a typical phase plug. There is no tapered expansion as the cross section shows the TAD is designed. All tapered expansion is horn or adapter dependent. The driver itself terminates flush with the phasing components.
It is a very happy combination. Whether by chance or intent I cannot say but I have yet to find anything that does it better. The 2441's are wonderful and have their own qualities but I cannot say they are all around better.

grumpy

08-25-2006, 02:17 PM

All that aside, what will sound best in a home environment is the issue at hand.

YYYep. That's why I hang around here listenin' ... :D
(mostly);)

-grumpy

Steve Gonzales

08-25-2006, 02:45 PM

[quote=Mr. Widget]Even a stopped clock is correct twice a day.

You could look at it that way, or it just may be that you finally recognize what time it is. :D

Zilch

08-25-2006, 03:20 PM

243x drivers use a two-stage phase plug terminating at the mounting face consistent with OA design guidelines. After considerable effort, I was able to secure an answer from JBL Pro (Button?) that they were indeed "compatible" with OA horns, though some (235x, for example) would require mounting flange modifications. Clearly, PT Waveguides are also "rapid flare" designs.

In question here is whether this phase plug (below) is "backward compatible" via throat extension with earlier horn designs as is apparently the case with 245x drivers. Are the phase plugs different in the 1.5" vs. 2.0" versions of those large format drivers?

What about Harman Consumer's use of 243x drivers? Do we consider H9800 and Array Series horns to be rapid flare?

Edit: Rob's pic of the diaphragm side of 2431 phase plug, bottom. I'm not seeing what's "two-stage" about it - the initial (~0.25") straight section before the flare? Looks like the outer ring might have a shorter path length due to the angular offset....

Mr. Widget

08-25-2006, 03:41 PM

What about Harman Consumer's use of 243x drivers? Do we consider H9800 and Array Series horns to be rapid flare?Nope... just another bi-radial... and you know what I think about those. :D

As for the Array Series... I haven't seen or heard them so the jury is still out. They may be good... tipping the H9800 on it's side may make it sound better too. I meant to give that a try when Giskard first showed us a pic of the Project Array Series... but it is fairly down on the list and hasn't happened yet. :(

Widget

Rudy Kleimann

08-25-2006, 03:53 PM

YYYep. That's why I hang around here listenin' ... :D
(mostly);)

-grumpy

I too have been doing a lot of listenin' here for the same reason. A lot of reading in the LHS Library, JBLPRO site, and others, to try to get a handle on what's going on and how to get it right.

This is what I think I've learned so far:

As you go down in frequency, the horn's dispersion/pattern control in the horizontal or vertical plane is largely influenced, yea, dictated, by the dimensions of the mouth of the horn.

Smaller vertical mouth dimensions are a balance/tradeoff between 1) a large versus smaller cabinet, and 2) (most importantly in home listening) maintaining good vertical pattern control versus vertical lobing/cancellation effects due to wider spacing between between the horn driver and the adjacent driver -in the range of frequencies near the crossover frequency.

In other words, the closer the drivers are as you look at the front, the less comb-filter and resulting lobing effects you hear as you move up and down in front of the drivers (with a lower 6dB/octave crossover slope making it worse over wider range of frequencies than a 12,18, or 24dB/octave rate), -but- the big drawback is that you lose dispersion control if the frequencies are low enough that the small vertical dimension of the horn can no longer control the dispersion. Below such a frequency the lower the frequency, the more the sound wave just diffracts over the lip of the horn, "spilling out and over" instead of being directed by the walls of the horn.

Check out the vertical dispersion pattern graphs on a 2380 horn and a 2352 horn at the JBLPRO site for a working example. Notice that below about 2-3KHz the 40-degree vertical pattern control just goes to hell on the 2380, where the 2352's advertised 50-degree vertical dispersion pattern control holds up well down to about 1KHz. That's the difference between a vertical horn flare dimension maintained to only 9.25" on the 2380 and 16" on the 2352.

Note also that the 2380A brochure states, "...the horn's small vertical mouth dimension (just slightly larger than the compression driver...) allows very compact systems..., that it "provides vertical pattern control to 2KHZ... Should vertical pattern control be required below 2KHZ, 2 or more horns may be stacked to restore full bi-radial performance."

When you consider how narrow the Smiths are vertically, is it any wonder they would have reflection problems well into the treble frequency range -perhaps up to 5KHZ or higher? without "lips" to extend/maintain the horn's vertical mouth dimension. The lower end of a driver's output connected to such a narrow horn would probably wrap way back around the mouth, creating all kinds of reflection issues -maybe even from the speaker baffle it is protruding from?

As far as the case of Steve Gonzales, is the absorbent foam just "absorbing" the ill effects of diffraction at lower frequencies? The "lips" would remedy the shortcoming in the first place, right?

As I stated above, I think I got it right. Do I? Giskard? Widget? Zilch? Others?

Robh3606

08-25-2006, 03:53 PM

Well here is the answer on the horn type if the add copy is correct

To achieve their superlative performance, the 1400 Array, 1000 Array and 800 Array loudspeakers feature advanced-technology Bi-Radial®-horn compression drivers mounted vertically in a freestanding configuration.

Rob:)

subwoof

08-25-2006, 04:52 PM

Well it's basic physics concerning the extended baffle. Just like any radiating source ( woofer on a baffle for example ) the usable LF response / curve is a function of the *length* of the return path to the energizing source.

The length of the horn might be the dominate function for the cutoff frequency but it's not the only story. This is mentioned in the JBL acoustic lens tech manual where it says the 2390 can be used lower provided a baffle is used.

This why the old D130's actually had decent bass when installed in a 60's popular basment infinite baffle, the WALL :) The return path included the couch, hallway, laundryroom, stairwell and the future kids room.

I agree that the extra length on the 2352 makes it a great horn for the 2435Be but the poor driver looks lost with all that horn and it's not that living room freindly.

As for steve's foam lips, I think the absorbtion was 20% and the added length was 80% what he experienced so duplicating / measuring / testing that would be one heckuva thread for the insomniacs amongst us.

:cheers:

sub

Ian Mackenzie

08-25-2006, 05:03 PM

Rob,

My last and probably dumb idea is a large conical wave guide.

It would be large to run down to 650 - 800 ....probably about 20 inches or so in diameter. A bit like Earl Geddes thing you would get really good power handling and low distorton. I still plan to buy the 14 incher (1500hz version) from Parts Express and give it a wirl.

Steve Gonzales

08-25-2006, 05:04 PM

Thank you for the info. I've got to get that bloody RTA that Zilch has prompted me to acquire. As usual, I rely on what my ears tell me sounds correct (to personal taste). Now if I could just figure out a way to have the baffle/lips, and have it not look like shizznite.

Zilch

08-25-2006, 05:19 PM

I agree that the extra length on the 2352 makes it a great horn for the 2435Be but the poor driver looks lost with all that horn and it's not that living room freindly.How about the Vertec waveguide then (below)? Kinda like 2396. P-Audio makes one, too, for 1".

There's the round-to-rectangular transition throat some have been seeking. Just saw it off at the appropriate crossection.

[I'd have trouble calling that "rapid flare," I think.... :p ]

Zilch

08-25-2006, 06:02 PM

I've got to get that bloody RTA that Zilch has prompted me to acquire.Ian just posted in another thread:

http://www.enjoythemusic.com/magazine/equipment/0705/behringerultracurve2496.htm

$250 at Guitar Center. Ask 'em to throw in the mic and cables for that, too. ;)

subwoof

08-25-2006, 06:37 PM

The 2396 is a modified throat from the big 2365 horn and I actually played with a pair for awhile. JBL had 'em in the original 1997 sale for 20 bucks..

Flushing that horn into a baffle creates a pure slit source and without some guidance it might be a little difficult to integrate BUT it sure could re-part someones hair line when sitting on axis...

But I think all this can be put to rest by installing a pair of 2360's in the living room and telling all listeners that it's gonna gound great.

Put seatbelts on the couch and sandbags by the door.

If you can't dazzle them with brilliance, baffle them with bullshit

:D

Ian Mackenzie

08-25-2006, 06:45 PM

Seat belts..with JBLs......what?.....We need Air-Bags:D

doucanoe

08-25-2006, 08:05 PM

how about this?

RC

Zilch

08-25-2006, 08:37 PM

how about this?
YEOW!! Those'll peel the wallpaper, if you're not careful. :p

Flushing that horn into a baffle creates a pure slit source and without some guidance it might be a little difficult to integrate BUT it sure could re-part someones hair line when sitting on axis....Well, now we've gotten down to my response to Rudy's question:

I conceptualize the Smith horn as a segmented horizontal diffraction slot. The cylindrical baffle or "lips" control the vertical diffraction pattern.

But, what's the polar response in the horizontal, in detail? Do the individual segments beam with increasing frequency creating lobes of a different sort, i.e., not from interference, rather, from power response attenuation?

Indeed, at 8 kHz they're 3 dB and not shown above that frequency in the "Lateral Dispersion" plot:

http://www.jblpro.com/pub/obsolete/2397.pdf

"Because of the action of the power distributors, the 2397 is notably free of high-frequency beaming, and maintains its effective 140° coverage to the highest audible ranges, with only minor lobes appearing above 5 kHz."

If their magnitude above 8 kHz were known, would they still be considered "minor" in the context of the smooth power response control achieved with newer design horns and waveguides?

And finally, as bottom line, is 140° horizontal dispersion even desireable in a home system? Not according to JBL's current "state-of-the-art" design guidelines....

*****

With the 2396 mounted vertically, the uncontrolled horizontal dispersion is 160°, as I recall, a "feature" touted for their use in Concert Series stage monitors. Think 2405.

See Don's post regarding rotating the slot vertical here:

http://audioheritage.org/vbulletin/showpost.php?p=108972&postcount=12

Zilch

08-26-2006, 01:08 AM

Check out the vertical dispersion pattern graphs on a 2380 horn and a 2352 horn at the JBLPRO site for a working example. Notice that below about 2-3KHz the 40-degree vertical pattern control just goes to hell on the 2380, where the 2352's advertised 50-degree vertical dispersion pattern control holds up well down to about 1KHz. That's the difference between a vertical horn flare dimension maintained to only 9.25" on the 2380 and 16" on the 2352.

Note also that the 2380A brochure states, "...the horn's small vertical mouth dimension (just slightly larger than the compression driver...) allows very compact systems..., that it "provides vertical pattern control to 2KHZ... Should vertical pattern control be required below 2KHZ, 2 or more horns may be stacked to restore full bi-radial performance."More info on that here, including height vs. frequency chart:

http://www.jblpro.com/pub/technote/tn_v1n07.pdf

Clearly, stacking's no panacea, either, as it becomes multiple sources lobing throughout the entire frequency range....

doucanoe

08-26-2006, 06:43 AM

YEOW!! Those'll peel the wallpaper, if you're not careful. :p

I thought they would also but surprisingly not that bad at all. I bet they would be a little edgy with SS but with low powered tube they are sounding sweet as peaches. Until I also find the right horns, Im going to ride out the storm with those. :D

RC

Rudy Kleimann

08-26-2006, 10:14 AM

I agree that the extra length on the 2352 makes it a great horn for the 2435Be but the poor driver looks lost with all that horn and it's not that living room freindly.

As Zilch once said in the Q&D thread, that horn/driver combo "looks like a bug on a tricycle":p And that horn ain't small or pretty by itself, that's for sure.

I wasn't referring to the length of the 2380, 2352, and the Smith horns, but the horizontal and especially the vertical size of the mouth of the horn and its substantial impact on pattern control.

As I understand it, baffle size would have little or nothing to do with pattern control, except for wavelengths that are so long that they diffract around the corner of an abruptly ending horn flare (a Smith horn has virtually no vertical flare to it, just a rounded edge to it). Energy at these long wavelengths would basically radiate into a 1/2-space (180 degree) pattern in the vertical dimension, gradually reducing the radiating pattern into the horn's design control pattern as the frequencies went up and the wavelength became short enough that the horns' small vertical dimension can maintain control of them. In the case of a Smith horn it seems that this would be happening into a fairly high frequency, causing lots of reflection problems in the lo-end if the horn is used down to lower frequencies, and not a problem once the frequencies are high enough that the small vertical mouth can maintain control.

Correct me as required-:hmm:

As for Steve's foam lips, I think the absorbtion was 20% and the added length was 80% what he experienced so duplicating / measuring / testing that would be one heckuva thread for the insomniacs amongst us.
sub

I'm wrestling with the thought that soft absorbing foam could possibly serve as an extension of the horn, much less a baffle. In my mind I would've thought it was 80-100% absorpsion and 0-20% (at best) added mouth size in the vertical plane. If it is made of styrofoam or similar, I would think it would act as an extension of the horn mouth dimension or serve as a baffle for it that would stop vertical diffraction at the lower end of the horns' range. In that case, I would agree with subwoof.

What are the JBL "lips" made of? Hard or soft material? What about Steve G's?

Rudy Kleimann

08-26-2006, 11:06 AM

More info on that here, including height vs. frequency chart:

http://www.jblpro.com/pub/technote/tn_v1n07.pdf

Clearly, stacking's no panacea, either, as it becomes multiple sources lobing throughout the entire frequency range....

'zactly, Zilch.

Regarding lobing in my first post, I was talking about interference-induced lobing effects from multiple drivers reproducing the same frequency, specifically a midrange and horn through the crossover region. This would cause strange irregularies in frequency response in the range of frequencies near the crossover point as your ears move off-axis. The same lobing problem would be true for multiple horns or multiple drivers of any type, but who wants or needs that in home hi-fi anyway?

Back to diffaction: To me, that is exactly what the "lips" for the Smith horns are for: to maintain pattern control in the vertical plane to a much lower frequency than the wood horn can do alone. In the case of a smith horn, it sticks way out beyond the baffle, so diffraction pattern at low frequencies would be even more than 180*, right? Talk about reflection problems?

What I was getting at is that a smaller horn allows you to get the drivers closer together (midrange and tweeter, for example) and that reduces the off-axis irregularity problems in the frequency range near the crossover frequency, but if one is driving a horn, you must realize that the horn will turn into a diffraction slot with near 180-degree dispersion if used down to a frequency lower than the small mouth dimension can control. If you want 180-degree dispersion, fine. But if you are trying to control the dispersion pattern, you must use the horn above the frequency where pattern control becomes effective.

Zilch

08-26-2006, 12:34 PM

The trick seems to be to match the directivity of the horn and the crossover frequency to that of the lower frequency driver at that frequency, at least in the horizontal, so that the two sources blend coherently. From there on up, the objective is constant directivity and power response, such that the reflections may then be uniformly handled by the room.

In 4430, for example, the 2344(A) 100° beamwidth in both axes is matched to the 2235H diaphragm dispersion of 100° at 1 kHz.

For a 12" woofer, the target frequency would be ~1.2 kHz. An 8" woofer and an 85° horn wants more like 2.4 kHz for a seamless blend....

Steve Gonzales

08-26-2006, 12:35 PM

[quote=Rudy Kleimann]

The same lobing problem would be true for multiple horns or multiple drivers of any type, but who wants or needs that in home hi-fi anyway?

Well Rudy, I'm guilty of that. I do my own thing in regards to my setup. I've been very careful to not recommend it as what to do (multiple pairs), and have always stated that it is just what I like. I will say this though., and this is where it gets tricky, well I do appreciate the science, it sounds pretty damn good. I've seen some unorthodox configurations in my time, from some kid with every speaker he could get his hands on, piled up and stacked, to massive full horn W.E./Altec/JBL systems in ridiculously small rooms. I fall somewhere in between. Unorthodox, but I also know how a great system sounds too. I wouldn't continue to keep running my side by side pairs if it didn't sound very good. I believe that I know what good imaging is, what a great soundstage is, etc-etc. So, therein lies the paradox. On paper, it would seem that there isn't a snowball's chance in hell that it should sound as pleasing as it does. Are there compromises? Yes. Do they outweigh the reality of how it actually sounds? Not to me or to quite a few friends that range from the very informed to not-so-informed (in the technical aspects). The addition of the foam lips makes the 2397's more focused. They didn't ever sound harsh or anything. Thank you for the explanation. I appreciate it and value it.

Rudy Kleimann

08-26-2006, 04:38 PM

I agree 100% Steve! If it sounds good, that's all that matters. If it's fun, play on!

I certainly don't want you to feel I'm faulting you for your setup. You are obviously enjoying your JBL system now, whereas my dream system exists only "on paper". Finishing my house takes priority in time and dollars. In the interim I make do with a pair of JBL L166's.

This thread (and many other threads I've read on this forum) have served as an exercise in Engineering design Philosophy for me to learn by. I've got quite a bit of JBL Drivers, horns, and cabinets sitting in storage, but I haven't decided what of them I'll be using yet.

Since I don't have the budget or test equipment to try all kinds of prototypes, I do all I can to read and learn by what others have done. This site and the JBLPRO site have taught me a lot already; hopefully I can avoid costly mistakes in my design by trying to apply all I can from the work of others.