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Two-way Compression-driver setup

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Posted on May 20, 2020 at 19:45:51
PaulF70
Audiophile

Posts: 1425
Location: Midwest
Joined: June 30, 2006
 Years ago I had Ah! 300 horns with some compression driver atop a bass cab.

I think it was possibly the best sound I've ever had.

I've been running mainly ESLs for years now, trying many direct-radiator cone/dome speakers, and none can match them for transient speed and thus realism, and so all leave me cold.

So I think I should try horns again after a decade and I think it should be a wideband compression driver. I understand they don't go high and don't care. I don't need the treble.

What are the best commercial and DIY options?

 

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RE: Two-way Compression-driver setup, posted on May 21, 2020 at 03:19:16
Scholl
Distributor or Rep

Posts: 1358
Joined: March 8, 2001
 I don't see any activity from Steve Woods.

Other possibilities are to find Steve Schell from Cogent or Johnathan Weiss from Oswalds Mill Audio. Those two people worked together for a while in the early 2000s on conical horns and may be helpful if they're still in business too. IDK

 

RE: I searched for Ah! 300 horn and,, posted on May 21, 2020 at 07:31:34
B. Scarpia
 Got pages of these:


Even my B&C's can't compete with those.

 

I agree, posted on May 21, 2020 at 15:04:54
Jon L
Audiophile

Posts: 6065
Joined: April 6, 2000
 A good compression driver on top of good woofer is so much simpler to get right than 3-way, 4-way horn designs. A lot of people who try this with 2" compression drivers usually end up adding a tweeter later on, but if you really "don't need treble," there are some nice 2" drivers out there these days and horns form places like Parts Express

 

RE: Two-way Compression-driver setup, posted on May 22, 2020 at 20:18:53
Mats Gunnars
Audiophile

Posts: 387
Joined: May 7, 2006


This would have to be my personal benchmark for a two way set up.
WE 24a with 555 driver, floating above a 50 Hz horn.
Image from emia gallery. Chicago friends may recognize
Kurt's faux marble AN 300b kit that made its way to Jeffrey.
The natural ease and freedom of the 24a
is hard to describe. I simply had no idea it could be like this.
Unobtainium, but something to aim for.
And yes, there might have been a touch of fostex in there.
Best wishes for your search,

Mats

 

RE: Two-way Compression-driver setup, posted on May 23, 2020 at 10:47:54
Jim Hodgson
Audiophile

Posts: 399
Location: New York City
Joined: March 9, 2006
 You asked: "What are the best commercial and DIY options?"

I'm not sure there are any commercial options -- let alone any reasonably-priced commercial options. My experience has been that this realm gets pretty lonely pretty quickly.

You're in luck, though, as there seems to be pretty good consensus around the following recipe: Altec 414 12" woofer in modern repro Altec 614 cabinet below; with Altec 1" compression driver on any number of 1" horns above. See link for details. Also, search here on Audio Asylum for Joe Roberts's (and others') posts on this configuration of parts -- along with some simple crossover ideas.

Some variation of the Altec 802 is typically used on the 1" horn. I tried a bunch: 802-8D and 804A, JBL 2421, Fostex D272, TAD TD-2001, and some current non-alnico drivers, too. (They all worked.)

You said: "I understand they don't go high and don't care. I don't need the treble."

Hmmm ... that wasn't my experience(?) Almost all of the drivers I mentioned, and especially the TD-2001 and more modern units, are quite high-frequency-capable. You may not enjoy the directional nature of high frequencies from a 1" compression driver on these sorts of horns, however.

In general, Altec 32 is a popular horn for this -- and a safe bet. In my final version (pictured), I used Edgar 650 Hz tractrix, which allowed for a greater variety of driver mounting hole schemes. I did try the Altec 32C -- and also the JBL 2397, 340 Hz and 600 Hz LeCleac'h, 500 Hz tractrix, and ... believe it or not ... Altec 329A (which launched me in a whole different direction, so don't try those ;) And here's an outside choice: SEOS-12 waveguide, which is cheap ($56/pr), available again (after a long period of being out of stock), less directional, and less sensitivity-boosting (which is a benefit when trying to marry one of these compression drivers with a dynamic woofer).

In the end, it's the 414-in-614 component that forms a very stable platform for all kinds of experimentation in the treble region. I even replaced the horn/compression driver top end with an ESS "Great Heil" AMT at one point. It began to feel like there was no bad combination out there. They all just plain work.

Anyway! There are lots of people around who have tried this -- excellent advice on this forum and some others like HiFiHaven. Good luck!




 

RE: Two-way Compression-driver setup, posted on May 23, 2020 at 18:14:15
PaulF70
Audiophile

Posts: 1425
Location: Midwest
Joined: June 30, 2006
 Oh now you just crazay!

 

RE: I agree, posted on May 23, 2020 at 18:15:09
PaulF70
Audiophile

Posts: 1425
Location: Midwest
Joined: June 30, 2006
 I had AV Trios that never gave me the sense of goosebump realism the two-way system did.

 

How was the ESS "Great Heil" AMT?, posted on May 24, 2020 at 13:52:20
Jon L
Audiophile

Posts: 6065
Joined: April 6, 2000
 on top of the woofer box compared to compression driver/horn?

I am working with woofer boxes via active crossover, so the treble/mid portion can be interchanged easily. From 1" compression driver in Seos12 horn to planar tweeter array, pretty much anything sounds quite good with the woofer so far.
I see the price of ESS Great Heils have come down, and they would sit on top of the woofer box very easily. I thought about trying a pair, but I have seen too many people condemn its large peaks/dips in frequency response, saying large corrections are needed in the passive crossover to sound good.

 

RE: Two-way Compression-driver setup, posted on May 24, 2020 at 14:35:47
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 I am running a Beyma CP755TI with 18 sound XT1646 horn crossed at 1khz to a Supravox 215-2000 wideband driver in a TQWT cabinet. You could easily use a 12-15 inch woofer with that driver/horn but I used what I had. Sounds phenomenal.

 

RE: How was the ESS "Great Heil" AMT?, posted on May 24, 2020 at 16:55:53
Jim Hodgson
Audiophile

Posts: 399
Location: New York City
Joined: March 9, 2006
 "I see the price of ESS Great Heils have come down."

Yes -- the price of all the Heil AMTs dropped significantly a year or two ago, if I remember correctly. I think this was related to the patent's timing out or ESS's losing it for whatever reason. I'm sure someone here knows. I recall paying $150 each during a New Year's sale; I see the price is currently $170 each.

"I have seen too many people condemn its large peaks/dips in frequency response."

I understand that the Great Heils are not everyone's favorite high frequency driver. And yes, people do seem to relish "condemning them," as you say. Honestly, I find myself so out-of-step with audiophile preferences -- not to mention knowing nothing about your tastes -- that I'd hesitate to make a recommendation. I'd probably be way off. That said, it sounds like you've got a pretty forgiving bass solution combined with a flexible crossover ... I'm not sure why you wouldn't give it a try? If you're in a position to do that, then I'm sure you're not overly worried about what other people say sounds good.

I'm not currently using the Great Heils, but I have no plans to part with them. They taught me a lot, especially about the reproduction of percussion instruments. That's an important reference to have. So, I'm certain that I'll return to them at some point either for a refresher lesson or for keeps -- who knows? In the meantime, here's a silly photo of my last experiment with them ... which solidified the fact that not every zany idea is necessarily meant to be.



 

Off topic Supravox thoughts, posted on May 25, 2020 at 08:34:30
Mats Gunnars
Audiophile

Posts: 387
Joined: May 7, 2006
 Lovely speaker that 215-2000.
Sounds like you have an excellent implementation.
Back a while I had first the alnico and later the field coil.
On an open baffle, the exc handing over to a 21" Madison at 60 Hz.
Killer Kraftwerk, but with more complex passages things fell apart a bit.
If I had the 215 now, I would try it from maybe 100 Hz,
leaving the bottom to something else. Acoustic Elegance?
How does your setup fair with Bruckner and Mahler?
Meanwhile, hope you're having fun!

Mats

 

Just put together round horn, posted on May 25, 2020 at 13:58:53
Jon L
Audiophile

Posts: 6065
Joined: April 6, 2000
 and this setup sounds crazy good, so much so that for my personal tastes and music genre, I might be done tinkering for awhile.




 

RE: Just put together round horn, posted on May 25, 2020 at 14:24:50
Jim Hodgson
Audiophile

Posts: 399
Location: New York City
Joined: March 9, 2006
 Excellent -- looks great!

Any photos from the rear? "How to support horns and compression drivers" is my perpetual research project.

 

Good question.., posted on May 25, 2020 at 14:35:32
Jon L
Audiophile

Posts: 6065
Joined: April 6, 2000
 I was in a hurry to test out the horns, so I just cut some thick packaging eggcrate which had a center groove and sat the compression driver on top.
The front of horn is sitting on one of those square cork/rubber footers.

It's very secure actually, so I may get lazy with building a permanent mount anytime soon... I mean it sounds so good the way it is, I don't want anything to change yet.





 

RE: Just put together round horn, posted on May 25, 2020 at 21:58:11
amandarae
Audiophile

Posts: 2591
Location: So.Cal
Joined: November 30, 2004
 Hi Jon L,
What horns are those?

Abe

 

Nice pic!, posted on May 25, 2020 at 22:00:40
amandarae
Audiophile

Posts: 2591
Location: So.Cal
Joined: November 30, 2004
 Hi Jim,
So that is the one that's on top of your 614 cas now?
The 414Z's sounds great since day one. Thanks again! I will try the SEOS horn , just for the heck of it. Very happy with the Azura horns so not really looking for a replacement but I need something to do.
Abe

 

RE: Nice pic!, posted on May 26, 2020 at 07:37:24
Jim Hodgson
Audiophile

Posts: 399
Location: New York City
Joined: March 9, 2006
 Hi Abe ... so happy you're back up and running! Yeah-give the SEOS waveguides a try. They're cheap enough to experiment with on a whim, and they have high percentage resale value when they go out of stock at DIY Sound Group.

The round horns on the 614s in the earlier photo are Bruce Edgar's 650 Hz tractrix (in poplar, I think). I used these with lots of different drivers, with the exception of the one I really wish I had tried -- TAD TD-2001.

There's no "now" with these anymore, though, as all of this stuff is in storage. (Which is why I never tried TD-2001 ... bad timing on my part.) I'd love to have these 2-ways at the ready in a second system, but there's just no room.

Here's another variation using John Hasquin's 500 Hz (I think?) tractrix in MDF. I used it for a while with JBL 2421 and then Fostex D272. Both of these 1" drivers seemed to want a tweeter, so I added a YL 1800G. I wouldn't say that these were an improvement on the recipe, though, and they obviously violated the simplicity.





 

RE: Two-way Compression-driver setup, posted on May 27, 2020 at 18:58:05
Oface
Audiophile

Posts: 1497
Location: columbia, south carolina
Joined: May 3, 2003
 I tried finding that SEOS-12 horn, and the sites said they were sold out.

Any hints to where I could find some available?

Thanks!

 

RE: Just put together round horn, posted on May 28, 2020 at 10:12:17
Jon L
Audiophile

Posts: 6065
Joined: April 6, 2000
 They are home-made 12" fiberglass horns

 

RE: Just put together round horn, posted on May 28, 2020 at 11:16:03
amandarae
Audiophile

Posts: 2591
Location: So.Cal
Joined: November 30, 2004
 Thank you Jon L!
I have similar setup with Azura 425 fiberglass horns.

Abe

 

Great Plains Audio-Altec 604, posted on May 29, 2020 at 08:00:00
Larry I
Audiophile

Posts: 2229
Location: No. Va.
Joined: June 28, 2000
 Great Plains Audio manufactures a modern version of the Altec 604 speaker. This is a two-way coaxial driver with a 15" woofer section and a compression tweeter in the center of the speaker. They sell only the driver and a two-way crossover, so you have to build, or get someone to build, the cabinet.

 

RE: How was the ESS "Great Heil" AMT?, posted on May 29, 2020 at 17:29:03
claudej1@aol.com
Audiophile

Posts: 817
Location: Detroit
Joined: August 17, 2007
 You may want to check out this thread in the Klipsch forum. MUCH SUCCESS there with the Heils.

https://community.klipsch.com/index.php?/topic/188177-double-stack-ess-amt-1-with-wings-possible-kit-for-heritage/page/29/&tab=comments#comment-2493526

 

Been following that thread but, posted on May 30, 2020 at 07:27:41
Jon L
Audiophile

Posts: 6065
Joined: April 6, 2000
 obviously, not everyone can produce woodwork results like those :)

 

RE: Been following that thread but, posted on May 30, 2020 at 15:11:56
claudej1@aol.com
Audiophile

Posts: 817
Location: Detroit
Joined: August 17, 2007
 Where there's a will, there's a way. Know any good carpenters?

 

Two-way Compression-driver setup, why it can sound so good, posted on June 1, 2020 at 22:40:52
Duke
Dealer

Posts: 4429
Location: Princeton, Texas
Joined: March 31, 2000
 In my opinion one of the advantages of doing a two-way (instead of three-way) with a single good horn-loaded compression driver has to do with the phase response, and specifically its implications for the time domain. Let me explain:

When the fundamentals and overtones arrive AT THE SAME INSTANT, the natural dynamic contrast is preserved. When we have smearing whether due to phase rotation or arrival time discrepancies or both, the dynamic contrast is compromised. This actually shows up as a loss of CLARITY because the all-important first-arrival sound is not maximally differentiated from other sounds, which arguably constitute a "noise floor" in this context. While there are other claimed advantages to good time-and-phase response, in my opinion this is the one that matters most.

(If we plan things out well, the physical depth of the horn adds the correct amount of path length to offset the phase-rotation-induced time delay on the direct-radiator woofer, relative to the compression driver, in the crossover region.)

Imo the disadvantage of using a second, much smaller horn for the very top end is, the tradeoffs involved in properly aligning the voice coils of the midrange and tweeter compression drivers. If we align them, then the mouth of the tweeter's horn will be behind the midrange driver's horn, and the tweeter's output will have a strong very early reflection off of the midrange horn. If we move the tweeter's horn significantly higher or lower or off to the side, the spatial discrepancy can be audible because the spacing will tend to be large, in terms of wavelengths at the crossover frequency. And ime we definitely do not want to overlap the top end of the midrange horn with the bottom end of the tweeter horn.

On the other hand if we don't properly align the voice coils of the midrange and tweeter compression drives (which would normally put the tweeter's voice coil a bit further back than the midrange's voice coil), then we have lost our time-and-phase coherence. Which is not the end of the world of course... and personally I'd chose this over having the tweeter's output reflect off the back of the midrange horn.

But imo better still to plan from the outset on using a single compression driver, even if there is some compromise in system bandwidth and/or efficiency. That being said, obviously many other designers have thought this over and come to a different conclusion.

Duke


Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.

 

AudioKinesis "Space Generator" and rear-firing compression driver, posted on June 2, 2020 at 08:07:50
Jon L
Audiophile

Posts: 6065
Joined: April 6, 2000



Boy, I haven't heard much about recent AK approaches, and upon looking, it's fascinating what you are doing with "space generator" firing backward 45 degrees up.

Also, some speakers seem to have the back of the compression driver drilled open to the rear via small waveguide as well. If compression driver dipole output is used with space generator below, will there be any problems with cancellation/augmentation at certain frequencies as well as phase?

As you've said, the overriding positive attribute of my 2-way horn system is uber Clarity. Will these rear-firing strategies mess with that clarity at all? I mention it because when i tried to somewhat imitate AK "Swarm" multiple sub approach, turning on the extra sub (sealed 10") in addtion to 2 main bass modules seemed to lessen the uber clarity.

 

RE: Two-way Compression-driver setup, why it can sound so good, posted on June 2, 2020 at 14:13:40
mnawaz3@aol.com
Audiophile

Posts: 502
Joined: March 28, 2002
 thanks for succint summary.

a good 4-way can be done (2 inmates here, merdy and hottatto) have outstanding multi-way systems which are dramatically better than the a good 2-way. but no question about it, a good 2-way can be easily implemented by almost anyone. so if quick results are desired, a 2-way is hard to beat. i have heard Jim's 2-way with 414 below an 1" altec driver and its hard to argue with you....until you hear a good 4-way.

for my personal biases, i dont think anything beats horn mid-bass..so for me, a 4-way is a necessary direction. however, if i cant get my horn 4-way to fly.,.. i may bail and end up with a 2-way line array and add a sub below 60.

 

RE: Two-way Compression-driver setup, why it can sound so good, posted on June 3, 2020 at 12:36:54
Duke
Dealer

Posts: 4429
Location: Princeton, Texas
Joined: March 31, 2000
 I agree that good horn-loaded midbass is magnificent.

And I'm sure there are things a good 4-way can do better than a good 2-way, and those certainly could outweigh the things a good 2-way can do well.

Before opening at an audio show I was in a room which had a two-way horn speaker with good time-and-phase domain behavior. A musician (vocals, guitar, piano) was also there, standing with his back to the system, which was at the other end of the room. The first song they put on to warm up the system was an acapella piece, The King's Singers' cover of Simon & Garfunkle's "The Boxer". The musician immediately whirled around with a stunned look on his face. In the brief instant between hearing the piece begin and wrapping his head around what he saw, he had been wondering when those singers had snuck into the room. He later told me that he'd never come close to being fooled by a pair of speakers before. In his experience there was live music, and there was reproduced music, and the one was unmistakable for the other with or without visual cues.

Not saying this is the only type of system which could have fooled a musician, but at least it's one of them.

Duke


Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.

 

RE: AudioKinesis "Space Generator" and rear-firing compression driver, posted on June 3, 2020 at 13:05:03
Duke
Dealer

Posts: 4429
Location: Princeton, Texas
Joined: March 31, 2000
 That's actually a second compression driver on the back of the cabinet, firing through that little elliptical horn. It has its own crossover, with its response tailored for its role.

The purpose of that rear-firing horn is to fill in just a little bit of reverberant field response. Let me explain:

I like to match up the radiation patterns of the midwoofer and horn in the crossover region. However with a rectangular horn, whose radiation pattern is 90 degrees wide by 50 degrees tall, some compromise is inevitable when trying to pattern-match with a midwoofer whose radiation pattern is axisymmetric. So I pattern-match the two in the horizontal plane, but then there is a relative scarcity of reverberant energy north of the crossover region because the horn's vertical pattern is only 50 degrees, whereas the midwoofer's vertical pattern had been 90 degrees in the crossover region.

This is where the rear-firing tweeter comes in. It adds a little bit of reverberant energy to fill in what's missing because of the main horn's limited vertical dispersion.

Now there are advantages to using a rectangular horn: The acoustic centers of horn and woofer can be placed closer to one another, and early floor and ceiling interactions are reduced. Also for listeners directly on-axis the "lips" around the horn's mouth are not all equidistant (as they are with a round horn), so there is no resulting on-axis-only response anomaly from an in-phase mouth reflection. Thus a rectangular horn augmented by a rear-firing tweeter could be seen as an attempt at "the best of both worlds".

I don't think there is any detrimental interaction between the rear-firing tweeter and the Space Generator, but subsequent models have done away with the rear-firing tweeter. This is because when that model, the Azel Stand-Mount, was built, the Space Generator section was considered optional. Since then we're either using round horns or considering the Space Generator to be mandatory, and we can use the compression driver in the Space Generator to take over the role of the rear-firing tweeter and fill any missing off-axis energy.

I'm surprised to hear that you found adding a third sub degraded clarity. My instinct is that one of the subs was either too loud or crossing over too high, or maybe two of the subs were in acoustically similar locations... either too close to each other, or both in corners, or otherwise in symmetrical locations. If the problem was too much very low bass, perhaps your scattered subs are combining in semi-random phase at the top end of the bass region (which is desirable) but approximately in-phase at the bottom end of the bass region because the physical distance between them is a relatively small fraction of a wavelength. In this case one solution would be to reverse the polarity of one of the subs.

When set up and level-adjusted correctly, I find the rear-firing horn improves clarity. I think this is because it is correcting the spectral balance of the reverberant energy.

If you decide to try adding a rear-firing horn, ideally you want its path length to add a minimum of 6 milliseconds of delay relative to the direct sound, and ideally 10 milliseconds or more. So placing it on the floor and aiming it at the ceiling may make more sense.

You will want its level to be adjustable, as there is a "sweet spot" you'll want to find. If it's too loud, clarity will start to be degraded. But below this threshold, timbre and spaciousness are enhanced with no downside. As a ballpark starting point, using pink noise, set the level of the rear-firing tweeter about 13 dB below that of the front-firing tweeter, as measured in your listening chair.

Also if you know that your main horn has an off-axis response anomaly, like perhaps it's a tractrix so it beams the highs, then theoretically you can tailor the response of the rear tweeter to "zig" where your main horn's off-axis response "zags". I have not actually tried this, because I use constant-directivity waveguide-style horns for my main horns, chosen in large measure for their good of-axis response.

Anyway best of luck to you!

Duke


Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.

 

RE: Off topic Supravox thoughts, posted on June 3, 2020 at 19:52:49
PaulF70
Audiophile

Posts: 1425
Location: Midwest
Joined: June 30, 2006
 I also ran Supravox field-coil 8" drivers in JE Labs OBs, and the sound was amazing!

In some respects. One of those "perfect except for three fatal weaknesses" scenarios.

 

RE: Two-way Compression-driver setup, why it can sound so good, posted on June 3, 2020 at 20:03:05
PaulF70
Audiophile

Posts: 1425
Location: Midwest
Joined: June 30, 2006
 "When we have smearing whether due to phase rotation or arrival time discrepancies or both, the dynamic contrast is compromised. This actually shows up as a loss of CLARITY because the all-important first-arrival sound is not maximally differentiated from other sounds, which arguably constitute a "noise floor" in this context. While there are other claimed advantages to good time-and-phase response, in my opinion this is the one that matters most."

This is the best way of putting this I've come across. So happy you chimed-in, Duke.

My last foray into a horn speaker was the JBL 4367. In many respects, they're amazing. Balanced, incredible dynamics, tons of detail with no fatigue. And measurements bear this out - they have astonishingly low distortion (in the FR domain).

Yet they didn't sound "right" against my Quad 63s - not as "live" or even dynamic. The Quads have that perfect "snap" of transient correctness. The JBLs can't do it. You want to turn them up more & more but it never helps.

I've concluded this (time & phase correctness in horns) can't be done properly, or at least optimally, with passive xovers. Active, particularly digital covers with delay, are the way to go. Agree?

 

RE: AudioKinesis "Space Generator" and rear-firing compression driver, posted on June 6, 2020 at 08:48:51
moray james
Manufacturer

Posts: 1599
Location: Calgary on the Bow
Joined: May 19, 2002
 Jon I prefer to place a comp driver on top of the cabinet (even the tweeter from a three way works for this) and then angle it so that I achieve the longest possible time/distance bounce and play with it so that it shoots its way back to the listening position and I do my best to match the bounce of both channels so they are the same time/length (or as close as I can contrive)so then the shortest bounce sets the limit of the other and I match the two as closely as I can. This generates the same type of spatial effect that you get with dipole loudspeakers while it is not a real effect it is never the less very nice to listen to as it can make the front wall disappear.
moray james

 

Tried backward firing tweeter, posted on June 6, 2020 at 20:01:17
Jon L
Audiophile

Posts: 6065
Joined: April 6, 2000
 "set the level of the rear-firing tweeter about 13 dB below that of the front-firing tweeter"

It so happens I have planar tweeter arrays that are about 12-13 dB less sensitive than my front horns, so installed them to fire backward to see what happens. Honestly, I expected a mess of a sound due to the haphazard nature of my experiment, but I was surprised to find very subtle sound differences only and nothing negative really. My front horns are round, so the little backward energy probably wasn't needed.

"I'm surprised to hear that you found adding a third sub degraded clarity. My instinct is that one of the subs was either too loud or crossing over too high, or maybe two of the subs were in acoustically similar locations"

I lowered the sub crossover point, moved it a bit farther away from the other woofer modules, and rotated it a little bit. Now I don't think the third sub degrades clarity, but I do hear what feels like a bit more velvety harmonic bloom surrounding voices/instruments. Certainly something to keep messing around with in the future, I think.

Thank you for all the detailed explanations above!



 

RE: Two-way Compression-driver setup, why it can sound so good, posted on June 10, 2020 at 21:51:10
Duke
Dealer

Posts: 4429
Location: Princeton, Texas
Joined: March 31, 2000
 "Active, particularly digital covers with delay, are the way to go. Agree?"

I suppose that's one way to go, but with careful driver and horn choices the compression driver's diaphragm ends up the correct distance behind the woofer to work well with an appropriate passive crossover. I've had good results with passive crossover where both acoustic slopes start out first order and then after a while accelerate symmetrically to fourth order. So imo digital isn't the one and only way to go.

Duke


Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.

 

RE: AudioKinesis "Space Generator" and rear-firing compression driver, posted on June 10, 2020 at 22:26:27
Duke
Dealer

Posts: 4429
Location: Princeton, Texas
Joined: March 31, 2000
 " I prefer to place a comp driver on top of the cabinet (even the tweeter from a three way works for this) and then angle it so that I achieve the longest possible time/distance bounce and play with it so that it shoots its way back to the listening position and I do my best to match the bounce of both channels so they are the same time/length (or as close as I can contrive)so then the shortest bounce sets the limit of the other and I match the two as closely as I can. This generates the same type of spatial effect that you get with dipole loudspeakers while it is not a real effect it is never the less very nice to listen to as it can make the front wall disappear."

EXCELLENT!!

Given a good recording, imo this allows you to hear MORE of the recording venue (whether real or engineered) and LESS of the playback room. This statement is counter-intuitive so let me explain.

There is in effect a competition between the acoustic signature on the recording (which is what we want to hear) and the acoustic signature of our inadequate listening rooms (which we'd rather not hear). The EARLIEST reflections are the ones which most strongly convey "small room signature". The LATER ARRIVING reflections convey less "small room signature", but immerse us in the decay of the recording venue's acoustic signature, so they convey a sense of envelopment in the recording venue.

By using that additional horn to add more later-arrival energy, which blends with the off-axis/reverberant energy of your front-firing drivers, you are in effect turning up the volume on the most spatially beneficial reflections without adding any more energy to the questionable early-onset ones.

A key element is avoiding early reflections, ideally by a combination of radiation pattern control and speaker positioning and aiming. If possible, we want a time delay between first-arrival sound and the strong onset of reflections. Kudos to you for doing this!!

The net result is that the venue cues on the recording are enhanced relative to the "small room signature" cues. The ear will essentially come up with the most plausible "picture" based on all the cues it receives, and will tend to ignore cues which do not fit. So even though it is highly counter-intuitive, by intelligently adding reverberant energy you end up hearing more of the recording venue (whether real or engineered) and less of the playback room!

Duke


Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.

 

RE: Two-way Compression-driver setup, posted on June 14, 2020 at 12:20:52
Jim Hodgson
Audiophile

Posts: 399
Location: New York City
Joined: March 9, 2006
 Damn ... sold out again? I bought mine from DIY Sound Group. I guess Erich had them again for just a minute. Sorry to generate enthusiasm and then have this happen :(

 

RE: Two-way Compression-driver setup, posted on June 17, 2020 at 03:30:49
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 Both of my systems are of this design concept.

My main system is the Odeon La Boheme speaker which has a 10 inch spherical (or tractrix...I am not 100% sure) horn with 1 inch compression driver (Beyma CP-350Ti) and a 10 inch mid/woofer (old Focal) loaded in a down firing TQWT back horn. Crossover is around 1500-2000hz and it sounds simply fantastic

My other system is a bit DIY, which started with a pair of Supravox Alizee that are single driver TQWT loaded speakers (using 8 inch Supravox 215-2000 full range drivers). On top of this I have mounted one or the other of two horn/compression driver combos that are stitched to the Supravox with a Mini-DSP nanodigi that is then feeding separate DACs and amps. THe crossover is optimized at 1000HZ.

THe horn/driver combos are the following: Iwata 600/Beyma CP-350Ti and 18Sound XT1464/Beyma CP-750Ti

The Iwata is from horns Poland and are taking into account findings from the LeCleach designs. The CP-350Ti is a 1 inch throat driver with pure Ti diaphragm and is good to 20Khz.

The 18 Sound XT1464 is a commercial plastic horn made with a sophisticated elliptical profile...it is constant directivity. The CP-750Ti is a 1.4 inch throat (3 inch diaphragm) made with Ti but with mylar surround. It is also good to 20khz.

Both sound great but somewhat different. THe bigger horn/driver is more robust and archetectural whereas the smaller horn/driver is giving finer detail in the upper ranges and a bit leaner as it gets towards the lower passband. I can't honestly decide at this point which I like better!

Good fun to swap them in and out though.

I think it gives the coherence of a single driver without all the flaws.

 

RE: Off topic Supravox thoughts, posted on June 17, 2020 at 03:37:34
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 When it is loaded in a TQWT cabinet it has surprisingly good bass punch and depth. I was going to design DTQWT cabs with some 10inch woofers but it sounds so good at the moment I put it on hold as it is pretty satisfying.

As a full range driver I found the 215-2000 to be a bit too rolled off in the highs but nicely alive.

 

RE: Off topic Supravox thoughts, posted on June 17, 2020 at 03:38:39
morricab
Distributor or Rep

Posts: 9181
Location: switzerland
Joined: April 1, 2005
 WHich is why I went to using it as a two-way and not OB but in a back horn type cabinet (TQWT).

 

RE: Two-way Compression-driver setup, why it can sound so good, posted on June 28, 2020 at 03:56:36
KanedaK
Audiophile

Posts: 2519
Location: Brussels
Joined: April 27, 2010
 Phase issues with horns... yeah. My system is far from being phase and time coherent, being three ways (with folded bass horn) + direct radiating subs, and tri-amped with analogue crossover.
It has me worried sometimes; but then when I listen to my system after listening to a more coherent, cone and dome system (for exemple, my friend's Focal 927Be), I don't cover my ears in awe because of the "horrible phase issues". Both sound like music to me, albeit with a very different flavor.

I already tried placing the tweeter more on the back, aligned with the midrange driver, and it wasn't "better" to my ears. No measurements, but in the end, my ears get to decide, so...

I suppose "in theory" it could be better, but in truth, I prefer the "sound" of analogue circuits, and I chose that compromise over another.

 

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