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In the Forum: Horn-Loaded Speakers
In the Thread: Earl Geddes: Horny Book
Post Subject: Do not spoil horns with dirty hands....Posted by Romy the Cat on: 7/19/2006

... or wondering if it has any new insight into horn design.

I did not read the book but I find funny that person who presumably do not “believe” in horn write a review about the presumably horn related book. It would be similar to ask a blind person to make a research about different ways to use colors by impressionists and post-impressionists …

  John Atwood wrote:
Where I part company with horn enthusiasts is their persistent denial of horn coloration, or the even more absurd claim that horns have better time response than other drivers (they don’t), or the horn somehow magically damps diaphragm resonances (it doesn’t). The most serious coloration are the modes, or resonances, induced by the horn itself…

I do not know who John Atwood is but he is apparently was catapulted form a different planet….

  John Atwood wrote:
To make horns, or any audio device, better, first we must understand how it works, and what causes the faults. Mindless defence of designs that date back to the late Thirties, and have seen little improvement since, has to give way to a better understanding of underlying principles, and most important of all, finding out if the underlying set of assumptions of the design are indeed accurate.

Well, I can stand when people cry about “design” but disregard the “Results”. I understand that they were for many years severally abused in theirs schools and not they pay revenge for that abuse stressing their “knowledge about design”. This would be fine if they in the end of the day were able to demonstrate a superior Sound based upon their “superior knowledge”. Unfortunately it is never was the case according to my experiences. I do not imply John Atwood, I know nothing about him but he sound kind of “recognizable”. Perhaps it would be better for him to be exposed once to a Not-Moronic horn installation (I have to admit – it is hard to find) and then he might reassess his views about the horns?

  John Atwood wrote:
The greatest impact of Thiele/Small LF design in the early Seventies was putting bass enclosure design on a rational and predictable basis for the first time in the audio industry. Prior to T/S, bass enclosures were designed by rules-of-thumb that could be off by as much as 6dB - in fact, there wasn’t even agreement how to measure them! After Thiele and Small, modelling provided actual closed and vented-box systesm that were within 0.5dB - or better - of the model. That’s the measure of how just much improvement a more complete understanding can provide. Similarly, Butterworth, Linkwitz-Riley, and modern Target Function Design (computer optimization) crossovers are far better than the grossly inaccurate “M-derived” filters of the late Forties, which were extremely complex and difficult to design - and worse, nowhere close to the performance of a real-word crossover.

It is VERY-VERY-VERY controversial statement.  Interestingly that since the early Seventies, when audio enterprisers accepted “rules of peculiar education” the Sound of commercial speakers begin to go down (with some exceptions of course) and still gradually going down.

  John Atwood wrote:
It’s not widely known that horn design hasn’t progressed all that much since the pioneering work of Bell Labs in the late Thirties. This provided the foundation for Altec and JBL theatre horns that became the basis for the modern high-efficiency speaker of today.

Altec and JBL… Good God! They were/are probably the most horrible horn implementations ever were made!!!

  John Atwood wrote:
The constant-directivity horns used in theatres and prosound today, unfortunately, are not about fidelity, but delivering peak SPLs to every seat in the house, and using digital EQ as necessary to compensate for the lumps and bumps in the horn response.

Yes, it is correct. There are many-many other reasons. Still, I wonder why John Atwood, acknowledging the very poor and faulty specific implementations attribute the negative results of those implementations to the entire class? If we see a bird with broken wings in the ground then we do not conclude the birds can’t fly….

  John Atwood wrote:
It’s all very nice that modern horns for hi-fi are made of NC-milled wood, have Tractrix or other unusual profiles, and have titanium or beryllium diaphragms, but the underlying horn theory is little different than what Bell Labs was using in the late Thirties. So the departures from the theory - the above-mentioned ripples in impedance, time response, and directivity - are still there.

Yes and no. Very little that was done in thirties has to do with result of contemporary horns. Find any Bell Labs, WE or RCA driver, with their original horns and listen it. It will be revolting (despite what the Morons says)  not because the “theory” but because very poor implementation that had no Sonic objectives, and partially for high demand of home listening.

  John Atwood wrote:
The most serious problem with existing horn theory is the assumption that the horn is of infinite length, which conveniently sets aside the real-world problems of reflections from the abrupt termination at the horn-mouth, which then travel back into the horn, reflect off the phase-plug or metal diaphragm, and return back to the horn-mouth, setting up a standing-wave.

I believe it was a paragraph about nothing. If you wish to use phrase “real-world problems” then use “real-world criteria to assess the values of those problems. To imply that the “real-world problems” could be viewed only in context of compliance with “irrelevant theory” is faulty things to do.

  John Atwood wrote:
Geddes’ Audio Transducers is the first book I’ve seen that sets aside the obsolete Webster theory, with its severe departures from the real world, and uses finite-element analysis instead. With this more powerful technique, the standing waves, or “High Order Modes” as Geddes refers to them, are revealed within the horn. At the lowest usable frequencies, horns behave like open-ended pipes, with a series of pipe modes that start at a quarter-wavelength of the horn length. At frequencies below this quarter-wave, the horn ceases to act like a horn at all, and response and power-handling drop very fast. The “cutoff frequency” of the horn is set by nothing more than the length of the horn, not the mouth size, nor the profile, nor the throat size.

I did not read the Geddes’ Audio Transducers book and I do not take Earl Geddes as something worth any attention. I do it since a last year someone pointed out to me that Earl Geddes is a bit inelectial freand with Wayne Parham, the dirt that runs “Pi Speakers” company. As far as I concern any individual who socializes with Wayne Parham, or even was in proximity of 1 mile from that asshole, should be shot right in his face with any mercy. I’m not kidding and I hope you got the message that I indented to pass. I wish Earl Geddes good luck with his “theories” and with his acquaintances.

  John Atwood wrote:
In Geddes’ commercial loudspeaker, the Summa, he takes the radical step of filling the horn itself with damping foam, sacrificing a bit of efficiency, but strongly damping the internal modes. The technique obviously works: the freq response vs directivity curves on the website are the best I’ve ever seen.

There are many “techniques”. The is even a theory (and implementations) of “hard horn”, according which the mouth of the horn is cover by another large diaphragm. Do we design speakers and concepts or we design Sound of the speakers? I did not heard Summa and I also did not heard Pi Speakers. I also, I did not read Mao Dze Dun books and would not go for George W. Bush lectures about strategy of scientific research….

  John Atwood wrote:
The superb curves are aided by Geddes’ thoughtful selection of drivers: the professional-grade B&C DE25 for the HF horn driver, and the B&C 15TBX100 15-inch driver for the bass. These are far better than the typical audiophile fare of 87 to 91dB/metre direct-radiator drivers from the usual high-end European sources. I did briefly audition the Summa at the last Rocky Mountain Audio Festival, but in all honesty can’t tell you how they sounded. I’m not being evasive here - as my readers know, I’m as opinionated as anyone in audio - but the Summas were powered by a bottom-of-the-market $200 Pioneer home-theater receiver and a $100 Panasonic DVD player from Costco.

I think George W. Bush should read his lectures in kindergarten, preferable for English no-speaking kind and preferable for deaf…

  John Atwood wrote:
If I understand Earl’s comments in Audio Asylum’s High-Efficiency Speaker group; correctly, he believes that mass-market electronics, DVD/CD players, and wires all sound the same, so the intelligent and thrifty buyer should save their money and buy home-theater electronics from big-box retailers. He was serious enough about this belief to rent a room for a thousand dollars at the RMAF show and demo his speaker with the electronics I mentioned above - I’m quite sure he was the only exhibitor using Costco-sourced electronics in the whole hotel. So what did I hear? A very accurately reproduced bottom-of-the-market Pioneer home-theater receiver and Panasonic DVD player. I listened, thanked Earl and his very gracious wife for appearing at the RMAF, dug into my pocket, and bought a copy of his book. If any of the readers of this blog are working on a loudspeaker, you *must* buy this book, and if necessary, get a physics or electronics major to assist you through the math. If any of the readers of this blog are in the market for a horn speaker designed by one of the world’s top designers, you owe it to yourself to audition this speaker. I have no idea whether Earl would respond favorably to having his speaker auditioned with audiophile, never mind vacuum-tube, much less 300B triode-powered exotica. If you read his comments on the Web page and the High Efficiency forum, Earl has strong opinions about the high-end industry, which must have made for some interesting encounters at the RMAF, which is a 100% audiophile show, no home theater on demo anywhere in the hotel. I must confess that I don’t understand Earl’s marketing strategy for the Summa, which is a technically elegant and sophisticated loudspeaker: in my experience, people buying entry-level home theater equipment don’t give a damn about sound quality, and listen quite happily to Dolby Digital, iPods, and MP3-compressed sound all day long. I don’t see how this home-theater demographic overlaps with the potential buyer of a multi-thousand-dollar state-of-the-art horn loudspeaker - the only horn enthusiasts I know are hard-core audiophiles with extensive record (yes, LP’s) collections numbering in the thousands, and have all-tube electronics which may or may not be cross-connected to a home theater system. Serious, extreme audiophiles, not Joe Sixpack listening to Pioneer electronics connected to a 32″ Wal-Mart color TV.

Hold on! Hold on! Whatever Mr. John Atwood, your Earl said is good for him what it has to do with your reviewing of the Lynn Olson’s book. Are you provide YOUR feedback to the Lynn Olson’s book or you keep polishing the Earl Gedd’s car?

  John Atwood wrote:
Maybe I don’t get out enough - there are several contributors in the High Efficiency forum who claim to have 1-kilowatt PA amplifiers driving 104 to 108dB/metre horn systems. A quick back-of-the-envelope calculation reveals a system like that could accurately reproduce peaks of 138dB at the listening position, enough to cause extreme pain, as well as immediate and total loss of hearing for life. (135 to 140dB is the sound pressure 1 metre away from the exhaust of a 747 engine at takeoff.)

Well, when you Mr. Atwood, stop to use High Efficiency forum of AA as the criterion of rational and intelligence not to say Sound then perhaps people would take you more serious. It is not only your readers would be benefited but even yourself, and your engineering thinking…

  John Atwood wrote:
Yes, horn enthusiasts are - how shall I put this as gently as possible - a little *different* then the rest of the audio world. Some are more different than others. This doesn’t change the fact that horns for the foreseeable future are the kings of wide-range dynamics and low IM distortion, and a tremendous amount of work remains to be done on the underlying theory. If you have a copy of H.F. Olson’s “Acoustic Engineering” or “Elements of Acoustical Engineering” on your bookshelf (and you know who you are), visit Earl’s website and buy a copy of Audio Transducers today. No, it’s not an easy read; it’s intended as a reference text, and belongs on the bookshelf of any serious audio engineer.

Hm, what was it? If it was a review of the Lynn Olson’s book that it was an unspeakably crappy review. If you have Harry Olson’s book then your have to buy Earl’s book… Come on! This is cheap even for the tasted of audio readers who have accustomed to read trivia trash in audio publications. I do not know what Earl writhes, honestly I care less about him because multiple reasons and one of them because his book is too dirty promoted (and this Mr. Atwood’s “review” of the Lynn Olson’s book is one of the illustrations). All that I learn about the Lynn Olson’s book after reading this “review” that it deserver more “interesting” readers then John Atwood was…

Rgs,
Romy the Cat

PS: Hm, after I posted it I realized that Earl Geddes was the person who wrote the book (my current PC suppresses images and I was not able to see the author of the book). I was under impression that Lynn Olson wrote some kind of horn book and John Atwood was trying to review it (the introduction mislead me). In this context my reply would have some “off the wall comments” but I decided to keep it  “as is”, as it was originally posted. I do not think that my major point would change…

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