For a test all these aspects must be assumed. I had not intended to write a detailed test protocol for commercial reasons
No permanent marks, but it did make me jump. Good thing the cap value was not so high, just the voltage rating.Never fun when that happens.Did it leave marks or knock you to the floor?
Originally Posted by Pano
Execpt of course that I have heard the Gedlee speakers get rough at high levels. Sounded just like distorting compression drivers to me.
The waveguides are very nice, but drive that little 1" Cd hard enough and you'll hear it.
A test like Art's would be great. An actual test of the audibility that any one can access. That would go a long way to convincing me and probably others. Remember the old saw about extraodinary claims and proofs? I'd be very happy if its true - but remain skeptical.
At one meter, yelling is around 100 dB. A pair of waveguides pointed at you would only need to be around 100-106 dB each at a meter to hit that level, trivial for a compression driver on a 60 degree waveguide, obviously not so trivial for small front loaded drivers like in your Vandersteens.
In my recorded tests, none of the compression drivers sounded bad (they still sound like the recording) at levels more than an order of magnitude louder, 110 to 116 dB at two meters from a single driver, at least no one that has played the recordings back has noted any problems at those levels.
The distortion (whether HOMs, THD or whatever deviation from the recording) did not become objectionable (depending on the driver and LF crossover point chosen) until peak levels were in the 120 dB range (at two meters).
Not to say that the Summas are not clean sounding and lack horn coloration at "normal" loud listening levels, but they certainly are not the only type of horn/waveguide that can do that, as my recordings of horn/drivers clearly demonstrate.
Until someone comes forward with some recordings of the Summas (with the same original recording also posted for comparison) at various SPL levels up to their thermal limits (which would be something like 10-15 dB louder than your yelling level observations), still sounding clean, I'm inclined to believe Pano's observation.
Art
Execpt of course that I have heard the Gedlee speakers get rough at high levels. Sounded just like distorting compression drivers to me.
The waveguides are very nice, but drive that little 1" Cd hard enough and you'll hear it.
A test like Art's would be great. An actual test of the audibility that any one can access. That would go a long way to convincing me and probably others. Remember the old saw about extraodinary claims and proofs? I'd be very happy if its true - but remain skeptical.
Patrick,
At one meter, yelling is around 100 dB. A pair of waveguides pointed at you would only need to be around 100-106 dB each at a meter to hit that level, trivial for a compression driver on a 60 degree waveguide, obviously not so trivial for small front loaded drivers like in your Vandersteens.
In my recorded tests, none of the compression drivers sounded bad (they still sound like the recording) at levels more than an order of magnitude louder, 110 to 116 dB at two meters from a single driver, at least no one that has played the recordings back has noted any problems at those levels.
The distortion (whether HOMs, THD or whatever deviation from the recording) did not become objectionable (depending on the driver and LF crossover point chosen) until peak levels were in the 120 dB range (at two meters).
Not to say that the Summas are not clean sounding and lack horn coloration at "normal" loud listening levels, but they certainly are not the only type of horn/waveguide that can do that, as my recordings of horn/drivers clearly demonstrate.
Until someone comes forward with some recordings of the Summas (with the same original recording also posted for comparison) at various SPL levels up to their thermal limits (which would be something like 10-15 dB louder than your yelling level observations), still sounding clean, I'm inclined to believe Pano's observation.
Art
Not to offend anyone, but frankly the Avante-Garde's, although highly reviewed and very expensive, are not very good by the standards of a correctly designed OS (Dr. Geddes' Summa) or a LeCleac'h horn system. Speaking only for myself, the AG Trios have an unfortunate combination of horn coloration and flattened dynamics and tone color. Horn coloration is common enough in commercial high-end systems (there was plenty of it in every horn mid or tweeter I heard at the RMAF) but flattened dynamics are unusual in horn loudspeakers. You expect things to jump out at you, and bright, vivid tone colors. To me, the AG's are dull, and I have no idea why. Maybe the diaphragms are not well-chosen, or the large fiberglass horns have selective frequency absorption.
Bjorn Kolbrek and I optimized the AH425 for uniform diaphragm loading over the working frequency range and the lowest possible diffraction; directivity control was not a concern except for avoiding nulls and peaks in the polar response. This simplifies crossover design, but the AH425 is not "controlled directivity" horn, nor was that a design goal. The polar pattern is very similar to a 2 to 3-inch direct-radiator, gradually narrowing as frequencies go higher.
To the best of my knowledge, the Summa has very low diffraction as well as precise control of directivity, and the crossover is quite complex, since it maintains a constant frequency response over a lateral arc at least 60 to 90 degrees wide.
Last night a band was playing thru our P.A. at a steady 95dB for 2 hours. It was loud, but not painful or harsh sounding. That was nothing more than 4 Meyer Sound CQ1 boxes and a sub. Peaks were about 10dB higher (mostly the sub, of course.) Didn't sound strained or too loud. Just loud enough for it to be fun and involving. In a large room, that's hard work for 4 compression drivers. But they didn't sound bad.
The Avant-Garde are one of the worst horns systems I've ever heard. I can't figure out how they can mess them up that bad. Really shockingly bad.
Pano,
Since the first time I ever saw a picture of the AG horns I just couldn't imagine that the designer had a clue how to integrate multiple horns. The spacing and the horizontal distribution of those horns makes little sense except for a visual appearance. I think people seem to think because a horn is round it will have little to no mechanical resonance but I don't believe that for a second. Just because something is a composite does not make it non-resonant, that is a major misunderstanding of material properties. You can have some awful bell modes happening in a round horn if the material is misapplied. I had the same reaction the first time I heard and Edgar horns, the integration was just totally out to lunch though I did enjoy talking to Bruce Edgar himself.
Since the first time I ever saw a picture of the AG horns I just couldn't imagine that the designer had a clue how to integrate multiple horns. The spacing and the horizontal distribution of those horns makes little sense except for a visual appearance. I think people seem to think because a horn is round it will have little to no mechanical resonance but I don't believe that for a second. Just because something is a composite does not make it non-resonant, that is a major misunderstanding of material properties. You can have some awful bell modes happening in a round horn if the material is misapplied. I had the same reaction the first time I heard and Edgar horns, the integration was just totally out to lunch though I did enjoy talking to Bruce Edgar himself.
The weird dullness of the AG's is the part I didn't expect; maybe it's as simple as a bad crossover error. I've tapped the fiberglass (or some kind of composite) AG horns, and no, they are not non-resonant. They have a sort of dull "thunk" to the sound when you tap them. The stands also wobble if you give them a bit of a push, so there's that to consider as well.
Martin's Azurahorns are a lot more rigid than what AG is selling. Haven't messed with Earl's horns, but sonically, they work as they should, and that's what matters.
Most of the commercially available horn speakers seem to have pretty bad crossovers. It doesn't help that horns require more sophisticated crossover design than direct-radiators. They are not as tolerant of out-of-passband radiation, they are more revealing of time misalignment, and many horns require substantial in-band equalization. You'd think with modern computer programs this would be pretty simple, but no, the expensive German and French high-efficiency speakers at the RMAF were pretty rough-sounding.
The most serious problem of hi-fi horn systems (aimed at consumers), going all the way back to the original Klipschorn, is poor system integration (as well as bad horns). The Khorn had a really rough region around 200~500 Hz, where the folds in the bass horn are causing lots of peaks and dips, and below the usable cutoff of the fairly small mid horn. The 1~2 kHz region of the Altec 604 Duplex is notorious among speaker designers. Lowther's, 'nuff said. The Ranger-Paragon. The list goes on.
That's why I have to give credit to Dr. Geddes for cutting through fifty years of scary-sounding horn systems, as well as a tip of the hat to Newell and Holland.
Martin's Azurahorns are a lot more rigid than what AG is selling. Haven't messed with Earl's horns, but sonically, they work as they should, and that's what matters.
Most of the commercially available horn speakers seem to have pretty bad crossovers. It doesn't help that horns require more sophisticated crossover design than direct-radiators. They are not as tolerant of out-of-passband radiation, they are more revealing of time misalignment, and many horns require substantial in-band equalization. You'd think with modern computer programs this would be pretty simple, but no, the expensive German and French high-efficiency speakers at the RMAF were pretty rough-sounding.
The most serious problem of hi-fi horn systems (aimed at consumers), going all the way back to the original Klipschorn, is poor system integration (as well as bad horns). The Khorn had a really rough region around 200~500 Hz, where the folds in the bass horn are causing lots of peaks and dips, and below the usable cutoff of the fairly small mid horn. The 1~2 kHz region of the Altec 604 Duplex is notorious among speaker designers. Lowther's, 'nuff said. The Ranger-Paragon. The list goes on.
That's why I have to give credit to Dr. Geddes for cutting through fifty years of scary-sounding horn systems, as well as a tip of the hat to Newell and Holland.
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The Avant-Garde are one of the worst horns systems I've ever heard. I can't figure out how they can mess them up that bad. Really shockingly bad.
I'm not one to "pile-on", but that's what I've heard from them as well.
It' *could* have been down to the dealer not "breaking-in" the mid driver (..which I believe is NOT a compression unit). So for me at least the problems I heard might well have been related to that "new" compressed/flat sound.
I'd also note that the tweeter section seemed more of a "gimmick" to me, not well integrated (..in what I believe was their "duo" from a few years past). I didn't listen more than 10 feet away from them however.. but if the integration window is that bad, then what's the point? (..the mid. horn probably should have raised up some and focused downward for better integration - but that of course would have ruined the industrial aesthetic.)
It's possible the 3-to-5 inch mid driver of the AG horn has a Kevlar diaphragm, or one of the other "space-age" materials. If that's true, then the diaphragm will be a heavier than the usual paper, and the HF breakup modes much more aggressive. Companies like B&W get away with Kevlar because of very sharp crossovers; the multiple HF breakups don't lend themselves to notch filters, because there as so many of them.
Horns will not magically damp diaphragm breakup; in a way, the bad effects of cone breakup are worse, because the wavefront going into the horn is no longer planar, but a more complex shape due to the multiple centers of radiation (which are not in phase with each other).
As a side note, Gary Dahl is reporting much better success with supertweeter integration with the beryllium-diaphragm Radian 745Neo (compared to the previous aluminum-diaphragm models). His supertweeter is a modestly-priced Aurum Cantus (Chinese) ribbon, not the extreme RAAL models I have, so that's an interesting find on Gary's part.
His guess (and I agree) is the HF response of the beryllium isn't as rough as the aluminum, and this simplifies integration. (Phase response goes through rapid variations in the breakup region, which does wacko things to the polar pattern when two drivers are summed acoustically.) The big difference between beryllium and aluminum is considerably better self-damping (quicker return-to-zero). It's most measurable at HF, resulting in smoother response, but the impulse response in the midband is better as well.
Horns will not magically damp diaphragm breakup; in a way, the bad effects of cone breakup are worse, because the wavefront going into the horn is no longer planar, but a more complex shape due to the multiple centers of radiation (which are not in phase with each other).
As a side note, Gary Dahl is reporting much better success with supertweeter integration with the beryllium-diaphragm Radian 745Neo (compared to the previous aluminum-diaphragm models). His supertweeter is a modestly-priced Aurum Cantus (Chinese) ribbon, not the extreme RAAL models I have, so that's an interesting find on Gary's part.
His guess (and I agree) is the HF response of the beryllium isn't as rough as the aluminum, and this simplifies integration. (Phase response goes through rapid variations in the breakup region, which does wacko things to the polar pattern when two drivers are summed acoustically.) The big difference between beryllium and aluminum is considerably better self-damping (quicker return-to-zero). It's most measurable at HF, resulting in smoother response, but the impulse response in the midband is better as well.
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Here is what I could find on a search:
6moons audio reviews: Avantgarde Acoustic Duo Omega retrofit
..heavy stock paper and ceramic OR alnico, and not a compression driver. (..the first driver pic. on that page is the rear of the compression tweeter.) The mid.s design makes sense though when you consider how low they operate that driver - well below the horn's profile. It's mostly "dust-cap" though, and I'm not sure it will ever "break-in" properly (because it's not simply a matter of loosening-up the surround and spider).
Apparently they have gone through several generations of the design, so who knows what it is today?
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Scott, that's one of the funniest reads I've had in a while. Thanks for brightening my Sunday (actually, I'm in pretty good mood, but I can always use a LOL moment).
My favorite line is: "Avantgarde horns are known for their qualities in the midrange." Note the author didn't say good qualities. My father was a diplomat in the US Foreign Service, and taught me when I was no more than 14 that you always have to look for missing words or phrases. What does the author not say? What subject is being avoided? Are there signs the document has been edited by someone other than the writer (awkward cut-and-paste, or the most important point moved to the end)?
Extra credit subject: Why do I think my father might have been CIA? My parents met in the OSS (direct predecessor to the CIA) during WWII, and he told me a lot of things about the CIA-sponsored overthrow in Iran that weren't publicly revealed until the Church Committee hearings in 1975. I had an interesting political education ... how to scan publicly available journals for missing information, planting articles in foreign newspapers so they would re-appear in US newspapers, etc. Much came out in the 1975 hearings, but I had heard it 10 years before, as a teenager growing up in Hong Kong.
My favorite line is: "Avantgarde horns are known for their qualities in the midrange." Note the author didn't say good qualities. My father was a diplomat in the US Foreign Service, and taught me when I was no more than 14 that you always have to look for missing words or phrases. What does the author not say? What subject is being avoided? Are there signs the document has been edited by someone other than the writer (awkward cut-and-paste, or the most important point moved to the end)?
Extra credit subject: Why do I think my father might have been CIA? My parents met in the OSS (direct predecessor to the CIA) during WWII, and he told me a lot of things about the CIA-sponsored overthrow in Iran that weren't publicly revealed until the Church Committee hearings in 1975. I had an interesting political education ... how to scan publicly available journals for missing information, planting articles in foreign newspapers so they would re-appear in US newspapers, etc. Much came out in the 1975 hearings, but I had heard it 10 years before, as a teenager growing up in Hong Kong.
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Yes, growing up overseas in the middle of the Cold War was interesting. We were posted to the Kobe/Osaka area of Japan from 1956 through 1961, and then went to Hong Kong from 1961 through 1966. This was at the height of the Red Guards madness in China, and HK was flooded with refugees ... probably a million went into HK while I was there. HK was chock-full of KMT (nationalist) and Red Chinese spies; every few months the HK police would find an apartment filled with propaganda and a small bomb.
The US Consulate was the size of an embassy in most countries, and was considered America's premier listening post into China back then. All kinds of antennas on the roof, and I remember Dad unplugging the phone as a matter of habit every time he went into his office. It was the first time I'd ever seen "Eyes Only" on a document folder. Turns out there are security classifications much higher than "Top Secret", which is actually a fairly low level of classification.
Dad went on mysterious trips about every month or so, bringing back oddball souvenirs like solid-tin cups and flatware from Indonesia. Check up Google to see what happened there in the mid-Sixties.
The most scary thing was attending the Hong Kong premiere of "Dr. Strangelove" and Dad telling me that he'd met Air Force generals just like the one in the movie. My parents both used the phrase "the balloon going up" as a reference to World War III, and knew the evacuation plans for Foreign Service families if it became necessary. They didn't tell me the details, but it involved a small boat that would go out to a submarine or aircraft carrier.
The evacuation from Saigon that happened ten years later was a horribly botched version of what I'd known when I was in Hong Kong; the US Ambassador was so drunk he commandeered a Jeep, was driven back to his personal residence, shot his piano, and returned to the Embassy for the last helicopter out of Saigon. True story.
The US Consulate was the size of an embassy in most countries, and was considered America's premier listening post into China back then. All kinds of antennas on the roof, and I remember Dad unplugging the phone as a matter of habit every time he went into his office. It was the first time I'd ever seen "Eyes Only" on a document folder. Turns out there are security classifications much higher than "Top Secret", which is actually a fairly low level of classification.
Dad went on mysterious trips about every month or so, bringing back oddball souvenirs like solid-tin cups and flatware from Indonesia. Check up Google to see what happened there in the mid-Sixties.
The most scary thing was attending the Hong Kong premiere of "Dr. Strangelove" and Dad telling me that he'd met Air Force generals just like the one in the movie. My parents both used the phrase "the balloon going up" as a reference to World War III, and knew the evacuation plans for Foreign Service families if it became necessary. They didn't tell me the details, but it involved a small boat that would go out to a submarine or aircraft carrier.
The evacuation from Saigon that happened ten years later was a horribly botched version of what I'd known when I was in Hong Kong; the US Ambassador was so drunk he commandeered a Jeep, was driven back to his personal residence, shot his piano, and returned to the Embassy for the last helicopter out of Saigon. True story.
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I think in this case the author's were "drinking the same Kool-Aid" as Srajan. "Known" as in re-affirming doctrine. (..both Srajan and the authors had this loudspeaker as "references" at one point.)
Srajan's tastes have changed quite a bit over the years..
What would be really interesting would be having him review those loudspeakers again, or even just their newer ones of the same model.
I'd bet that if that were done he wouldn't have such a favorable opinion of them, and he could probably tell you a lot more about why he liked individual aspects of the design, and where the loudspeaker failed - all with much more detail on all subjects. THAT would be an interesting read, but I suspect it's unlikely to happen (..because know one seems to like a negative review).
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I'd know idea that Indonesia went through those sorts of political problems. McCarthyism was sort of a "one day add" by comparison.
US sponsored and guided all the way through. Too bad about the 500,000 killed, and the decades of dictatorship that followed. Read about Peter Dale Scott's "deep state" if you want to learn more.
My dad went to Indonesia a year before the coup.
I don't think he was doing anything like "wet work", though. My best guess he was an analyst, since he hated the "cowboys" and the way they were always screwing up. He never lived to see the biggest screwup of all, the CIA/ISI/Saudi sponsorship of the most religiously insane Muslims in Afghanistan turning around and attacking the USA.
I turn the analytical skills he taught me to smaller projects; big frog in a much smaller pond. There's something satisfying about working with a simpler, more attractive palette, like improving loudspeakers. Nobody gets hurt, and some lucky people get to hear beautiful sound. That's why I do it.
My dad went to Indonesia a year before the coup.
I don't think he was doing anything like "wet work", though. My best guess he was an analyst, since he hated the "cowboys" and the way they were always screwing up. He never lived to see the biggest screwup of all, the CIA/ISI/Saudi sponsorship of the most religiously insane Muslims in Afghanistan turning around and attacking the USA.
I turn the analytical skills he taught me to smaller projects; big frog in a much smaller pond. There's something satisfying about working with a simpler, more attractive palette, like improving loudspeakers. Nobody gets hurt, and some lucky people get to hear beautiful sound. That's why I do it.
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Lynn,
Having done work with Kevlar composites I can't really understand why that material is used by itself as a diaphragm material in a speaker besides a small dome tweeter. While the material has some incredible properties in tensile strength its flexural modulus makes little sense for use alone as a diaphragm. I know when I bought Kevlar from Hexcel that I had to agree not to export the raw material as it was considered an advanced ballistic material at the time. It is a very difficult material to work with, just try and cut the raw fibers sometime, not a fun thing to do at all. I do use Kevlar in my diaphragm material but it is in combination with carbon fiber and works as a damper for the carbon fiber. I don't know much about the B&W mid driver but from what I have seen it does not have a normal surround but uses the Kevlar as a flexural edge treatment. The epoxy matrix resin is stiffer than the Kevlar itself and it is almost as if they use the Kevlar as a reinforcement for the epoxy itself. I would compare Kevlar to silk, they are more alike than anything else I can think of.
Having done work with Kevlar composites I can't really understand why that material is used by itself as a diaphragm material in a speaker besides a small dome tweeter. While the material has some incredible properties in tensile strength its flexural modulus makes little sense for use alone as a diaphragm. I know when I bought Kevlar from Hexcel that I had to agree not to export the raw material as it was considered an advanced ballistic material at the time. It is a very difficult material to work with, just try and cut the raw fibers sometime, not a fun thing to do at all. I do use Kevlar in my diaphragm material but it is in combination with carbon fiber and works as a damper for the carbon fiber. I don't know much about the B&W mid driver but from what I have seen it does not have a normal surround but uses the Kevlar as a flexural edge treatment. The epoxy matrix resin is stiffer than the Kevlar itself and it is almost as if they use the Kevlar as a reinforcement for the epoxy itself. I would compare Kevlar to silk, they are more alike than anything else I can think of.