Nearfield Bass Shootout

[Pete B]

Here is a question about the #7 vs. the #9 crossovers. If the first is more of a simple 2nd order corner and the second shelves before rolling off, is that due to different woofer response curves (different network needed for same combined response) or was AR moving away from pure 2pi thinking/measuring more towards achieving flatter response in 4pi anechoic conditions? I do believe they moved in that direction with the 3a Ltd (a UK influence?)

David

Hi David,

This was discussed here at length, we eventually found some mention

(or someone got in touch with Allison) that there was a bit too much

energy in the top end of the woofer's output - my rewording from

memory. It is very much like baffle step as I see it. Edit: Found it: People

were reporting that many early 3a's had the #7 inductor which lead to this discussion:

http://www.classicspeakerpages.net/IP.Boar...amp;#entry58138

I actually found in CALSOD that I had to use the 1.9 mH value (1.88 per spec)

for the #7 inductor to match the published input impedance curves for the AR-3a.

I started out with the 2.8 mH (2.85 per spec) value and I could not get reasonable

agreement. I also noted the difference in amplitude response which is easy to

plot in CALSOD as I'm sure you know.

[speaker dave]

Hi David,

This was discussed here at length, we eventually found some mention

(or someone got in touch with Allison) that there was a bit too much

energy in the top end of the woofer's output - my rewording from

memory. It is very much like baffle step as I see it. Edit: Found it: People

were reporting that many early 3a's had the #7 inductor which lead to this discussion:

http://www.classicspeakerpages.net/IP.Boar...amp;#entry58138

I actually found in CALSOD that I had to use the 1.9 mH value (1.88 per spec)

for the #7 inductor to match the published input impedance curves for the AR-3a.

I started out with the 2.8 mH (2.85 per spec) value and I could not get reasonable

agreement. I also noted the difference in amplitude response which is easy to

plot in CALSOD as I'm sure you know.

Thanks for the link, Pete. That definitely gets to the origins of it. As I interpret it, the motivation was to flatten the power response, (still in 2pi?) rather than in pursuit of a flatter 4pi anechoic curve. Obviously it would also tend to improve the baffle step issue, even though that doesn't seem to be the motivation.

I was looking at a couple of different published curves to see if the excess energy was evident in any. The Electronics World curve (room average of 9 positions with controls at max) shows a considerable bump (5 to 7 dB from 250 to 500). This curve seems at odds with any other that I have seen so I'm not offering it as definitive. Allisons paper (I'm looking at the Audio magazine version from 1971) shows generally raised midrange level from 200 to 5k. If I remember right the Allison measurements were made with level controls at max, for the sake of consistency. This would probably account for the 1k to 5k level, but lowering the mid wouldn't change the 200 to 500 level. On the other hand, wouldn't this be well after the inductor change?

It seems as though the change from Alnico to Ferrite was a secondary incentive for the inductor change i.e. it initially seemed like a drop-in, but eventually excessive mid level was noticed.

Re. the #7 choke being required for the right impedance curve: I can well imagine them deciding the curve with the original inductor was close enough, and not worth new artwork because of the inductor change.

Forensic Audio!

David

[Zilch]

NOW AIN'T THAT THE TRUTH!!!!

It's all we can do just to get past the "trivial."

The 99.9% in fact comprises 0.1% of the general population of enthusiasts....

[kkantor]

I guess that makes me a non-serious hobbyist, because 90% of this stuff goes right over my head. I've worked enough years in engineering testing and instrumentation to be able to ask some semi-intelligent questions about taking measurements, but understanding what measurements mean is another matter.

OK, OK, my post #99 went over like an Osmium balloon. I officially pretend I never wrote it.

-k

[soundminded]

I guess that makes me a non-serious hobbyist, because 90% of this stuff goes right over my head. I've worked enough years in engineering testing and instrumentation to be able to ask some semi-intelligent questions about taking measurements, but understanding what measurements mean is another matter.

You are not a true believer. You have no faith in over 100 years of countless thousands of people who studied acoustics, hearing, and electronics and the wealth of data and theories they've amassed that explains it all. You don't think they know what they are talking about because the results don't deliver on their promises both implied and explicit, namely that they will duplicate the auditory experience of hearing a live performance by great musicians playing great music in a great venue on the finest musical instruments in the world from recordings. And you are 100% correct and justified in your skepticism and cynicism. Endless variants of the same failed ideas over and over and over again, each new one touted as the magic bullet have resulted in an endless and consistent string of failures. They aren't even close. How can that be? At the end of the 19th century, physicists thought they'd had the universe pretty well figured out. Then Einstein came along and blew away everything they thought they knew exposing it as dead wrong. At first they wouldn't listen to him. Then they didn't understand what he was telling them. Then they couldn't believe it. Today the knowledge he gave us is not only unimpeachable so far, much of our current technology depends on it. Engineers in this field are just as arrogant as those physicists were.

Before you can have meaningful measurements and a way to interpret them, you have to have an understanding of what you are measuring. A model that is accurate to account for all of the variables that play a role and how they stack up in the performace of real equipment against the idealized model.

Among the things and the roles they play that are not understood well or at all are;

The acoustics of the recording venue

The acoustics of live venues

The variables of the way recordings are made

The acoustics of the listening room

The nature of hearing and how the human brain interprets what the ears tell it

Ironically, the performance of purely electronic equipment is nearly perfectly understood, the equipment pefected and inexpensive, and it no longer plays a role in the limitations of the process. But the things that are not understood that I listed above are not in the province of electronics or electrical engineering. All except the last one is an aspect of mechanical engineering. The last one is in the area of clinical psychology.

All of this required knowledge is either scant or non existant. All existing models are based on historic methods which were either intuitive or based on fallacies and gross approximations and generalizations which are highly inaccurate. Nobody capable of gaining insight into any of it seems interested. When you begin to approach a serious discussion of any of it the people who should be listening and thinking shut down their minds. All they want to do is go back to doing more of what they've been doing since they started. Small wonder they don't get anywhere. You can hit your head against the same brick wall forever without making it budge. Even though if you stepped back, it might make you realize it is easy to vault over it or go around it. Don't expect anything from these people except more of the same. And each new variant will be touted as the latest magic bullet that will slay the dragon. And each one will be more expensive than the last. That's one thing you can always count on. Another is that there will be people who believe them and go out eagerly to buy it.

[genek]

And you are 100% correct and justified in your skepticism and cynicism.

Figures. First time I'm 100% right about anything turns out to be this.

However, I was actually referring to my ability to understand what the measurements mean...

[speaker dave]

....Endless variants of the same failed ideas over and over and over again, each new one touted as the magic bullet have resulted in an endless and consistent string of failures. They aren't even close. .....All of this required knowledge is either scant or non existant. All existing models are based on historic methods which were either intuitive or based on fallacies and gross approximations and generalizations which are highly inaccurate. Nobody capable of gaining insight into any of it seems interested. When you begin to approach a serious discussion of any of it the people who should be listening and thinking shut down their minds. All they want to do is go back to doing more of what they've been doing since they started. Small wonder they don't get anywhere. .......Don't expect anything from these people except more of the same. And each new variant will be touted as the latest magic bullet that will slay the dragon. And each one will be more expensive than the last. That's one thing you can always count on. Another is that there will be people who believe them and go out eagerly to buy it.

Soundminded,

First, thanks for a repeat of your usual diatribe against the audio engineering community.

I'm not exactly sure (or, frankly, interested) in what has created your sour opinion of the industry. I'm certain I don't share it.

As a 30 year member of the industry, I have seen a lot of evolution personally, and as a student of audio history I am familiar with the steady evolution that proceeded it. For loudspeakers I have seen affordable tools for measurement and simulation of crossover networks, simulaiton of cabinets including diffraction effects, and woofer box systems. I have seen drivers steadily improve in response smoothness, reduce in distortion and increase in power handling, all at reduced cost. I have seen it become commonplace to design crossovers that give invisible in-phase summing of sections with lobing as determined by the designer. I have seen constant directivity devices with surprisingly uniform polar response. I have seen low diffraction cabinets that give response approaching infinite baffle mounting.

I have seen 1000 watt subwoofer amplifiers that run stone cold, subwoofer drivers that would survive their input, all in cabinets half the size of an AR3 and going an octave lower.

I have seen DSP systems that can dramatically smooth the response of a system in a room (still an evolving art), and loudspeaker arrays that can create 5 discrete channels by sending simultaneous highly directional sound beams at the various boundaries of a room (One Limited and those clever DSP engineers at Yamaha).

I've seen cabinets go from ugly square boxes to beautifully sculpted and rounded shapes. I've seen in-wall speakers that approach the quality of free standing systems and I've seen touch screen remote control systems that can easily control highly complex systems.

Digital recording, data compression schemes, flash memory, SACD, Blue-Ray......

"But it doesn't sound like live music." he laments. At its best I think it gets surprisingly close. Oddly, only music reproduction is saddled with the goal of totally fooling the senses. We don't walk away from a movie dissapointed that we weren't fooled by flashing images on a screen. "I never felt I was viewing into a real world." We are happy when cameras get sharper, megapixel counts increase, but we don't whine if the eye isn't fooled into seeing true reality. How could we enjoy a painting, with its inadequate reproduction of visual space? How could a play be enjoyable at all: cardboard backdrops, no reality there? Maybe the goal of a music system is to merely convey the body and emotion of the music, just as a painting conveys a small part of the essence or beauty of its subject.

I don't think the industry is perfect. High end audio is a poor combination of frequently subpar engineering and exhorbitantly costly products. This is one of your issues and I don't necessarily disagree. My greater lament is that the market for good equipment is shrinking. Fewer people care, the masses that once bought audio have moved on to cell phones, Blackberrys, flat screens and other electronic toys. The masses were never hard core enthusiasts, but when buying hi-fi was something that everybody did, it supported an industry that benefited those of us who really cared.

This is the real issue, technical progress requires an economic base. The Japanese have pulled out of hi-fi (anything beyond docking stations) because the market is too small. Who will advance audio without a mass market to provide the dollars? Even if a briliant person such as yourself developed a breakthrough total system (recording through playback) that gave you the realism you seek, how would you get recording practices adopted, software distributed, hardware launched and products sold?

It is true that most of our development has been of the constituent components of a standardized approach: 2 channel recording and stereo playback. I know from many demonstrations that 5 channel music is a significant jump in the "fooled that you were there" direction. Too few consumers are interested and the diehard audiophiles are mired in tradition to the point of rejecting anything but 2 channels for muusic. Manufacturers don't survive by making products without a market.

I guess I'm still an optimist. Maybe those kids with I-pods will eventually want something better than a docking station to plug into. Home theater still gives us an outlet for high performance sound and lets us sneak in multichannel music. Digital technology in all forms will have a lot of spin off benifits to audio.

I'd rather be involved in the evolution of audio than standing on the sidelines bitching about it.

David

[soundminded]

Soundminded,

First, thanks for a repeat of your usual diatribe against the audio engineering community.

I'm not exactly sure (or, frankly, interested) in what has created your sour opinion of the industry. I'm certain I don't share it.

As a 30 year member of the industry, I have seen a lot of evolution personally, and as a student of audio history I am familiar with the steady evolution that proceeded it. For loudspeakers I have seen affordable tools for measurement and simulation of crossover networks, simulaiton of cabinets including diffraction effects, and woofer box systems. I have seen drivers steadily improve in response smoothness, reduce in distortion and increase in power handling, all at reduced cost. I have seen it become commonplace to design crossovers that give invisible in-phase summing of sections with lobing as determined by the designer. I have seen constant directivity devices with surprisingly uniform polar response. I have seen low diffraction cabinets that give response approaching infinite baffle mounting.

I have seen 1000 watt subwoofer amplifiers that run stone cold, subwoofer drivers that would survive their input, all in cabinets half the size of an AR3 and going an octave lower.

I have seen DSP systems that can dramatically smooth the response of a system in a room (still an evolving art), and loudspeaker arrays that can create 5 discrete channels by sending simultaneous highly directional sound beams at the various boundaries of a room (One Limited and those clever DSP engineers at Yamaha).

I've seen cabinets go from ugly square boxes to beautifully sculpted and rounded shapes. I've seen in-wall speakers that approach the quality of free standing systems and I've seen touch screen remote control systems that can easily control highly complex systems.

Digital recording, data compression schemes, flash memory, SACD, Blue-Ray......

"But it doesn't sound like live music." he laments. At its best I think it gets surprisingly close. Oddly, only music reproduction is saddled with the goal of totally fooling the senses. We don't walk away from a movie dissapointed that we weren't fooled by flashing images on a screen. "I never felt I was viewing into a real world." We are happy when cameras get sharper, megapixel counts increase, but we don't whine if the eye isn't fooled into seeing true reality. How could we enjoy a painting, with its inadequate reproduction of visual space? How could a play be enjoyable at all: cardboard backdrops, no reality there? Maybe the goal of a music system is to merely convey the body and emotion of the music, just as a painting conveys a small part of the essence or beauty of its subject.

I don't think the industry is perfect. High end audio is a poor combination of frequently subpar engineering and exhorbitantly costly products. This is one of your issues and I don't necessarily disagree. My greater lament is that the market for good equipment is shrinking. Fewer people care, the masses that once bought audio have moved on to cell phones, Blackberrys, flat screens and other electronic toys. The masses were never hard core enthusiasts, but when buying hi-fi was something that everybody did, it supported an industry that benefited those of us who really cared.

This is the real issue, technical progress requires an economic base. The Japanese have pulled out of hi-fi (anything beyond docking stations) because the market is too small. Who will advance audio without a mass market to provide the dollars? Even if a briliant person such as yourself developed a breakthrough total system (recording through playback) that gave you the realism you seek, how would you get recording practices adopted, software distributed, hardware launched and products sold?

It is true that most of our development has been of the constituent components of a standardized approach: 2 channel recording and stereo playback. I know from many demonstrations that 5 channel music is a significant jump in the "fooled that you were there" direction. Too few consumers are interested and the diehard audiophiles are mired in tradition to the point of rejecting anything but 2 channels for muusic. Manufacturers don't survive by making products without a market.

I guess I'm still an optimist. Maybe those kids with I-pods will eventually want something better than a docking station to plug into. Home theater still gives us an outlet for high performance sound and lets us sneak in multichannel music. Digital technology in all forms will have a lot of spin off benifits to audio.

I'd rather be involved in the evolution of audio than standing on the sidelines bitching about it.

David

"First, thanks for a repeat of your usual diatribe against the audio engineering community."

What a slander to real engineers to call these people anything more than tinkerers. That is what they are and all they are for the most part. I'm not talking about those who design commercial amplifiers, DSPs, or other purely electronic equipment. I'm not talking about people who design loudspeakers for sound reinforcement systems. I'm not even talking about those who design convential electronic components. I'm talking about the people who claim to design high end audio equipment with a high end pricetag. This is not engineering by any stretch of the imagination. Before you can engineer anything, you need a firm grasp of the underlying scientific principles that your design embodies with clearly defined objectives and ways to evaluate whether or not the results of an engineering effort meet those objectives. People who design audiophile equipment do no such thing. Their ads merely blow smoke. If my engineering designs in my field fell as far short of their promises and expectations as audiphile gear does, I'd have starved in the street a long time ago.

"But it doesn't sound like live music." he laments. At its best I think it gets surprisingly close."

Close? To what? It can't even be made to sound like a real piano or a real violin in your home let alone like the Boston Symphony Orchestra at Boston Symphony Hall, or the Mormon Tabernacle singing in the Tabernacle, or the Metropolitan Opera singing at the Metropolitan Opera House. It only sounds close if you are half deaf...probably from listening to blaring sounds from rock bands or playing out in the traffic too long.

"Oddly, only music reproduction is saddled with the goal of totally fooling the senses."

It's the only one that defined that as its goal and promised that except maybe for art forgers and immitation perfumes. Entry to a movie theater doesn't cost tens or hundreds of thousands of dollars either. If this equipment actually came close to fulfilling its promise, there wouldn't be a newer improved version every other year and not only would they fool at least some of the people some of the time by now, but they would be converging in performance just like amplifiers and cd players have. If there is no interest in it anymore, it may be because most people don't think its mediocre performance justifies its price. I certainly don't and wouldn't dream of owing any of it. People have more enjoyable things to spend their money on.

"I'm not exactly sure (or, frankly, interested) in what has created your sour opinion of the industry. I'm certain I don't share it."

Now why doesn't that surprise me one bit?

BTW, the algorithms in the Yamaha DSP-1 were an infringement on my patent. I've explained why I didn't sue elsewhere. It is the crudest functional form possible that meets the criteria of that aspect of my invention....and it can be made to work if you know how to use it.

[kkantor]

There obviously are extremes.

At one end we have high-end buffs (and journalists) who seem to think that measurements of any kind (even basic ones like frequency response, bandwidth, and distortion) do not mean a thing, or at least do not mean much. A handful of magazines seem to work (or had worked in the past) this way. Often, the subscribers like this sort of approach to product analysis (especially when it comes to stuff like wires, isolation devices, and line filters) and do not want technical data messing with their world views. The magazine editors react accordingly.

At the other extreme we have those who measure the daylights out of something (speakers, amps, wires, surge protectors, etc.) and then simply cannot explain just what some (or often even most) of what those sometimes very esoteric measurements mean or how significant they are. Some product reviews involve a multitude of measurements, and then the reviewer summarizes his listening impressions by seeming to ignore the data completely, going on to rhapsodize about sonic characteristics that are out in left field. Certainly, many high-end amplifier reviews are this way, but some speaker reviews are this way, too.

For me, the idea should be to determine which measurements tell us something, and then go with them, while at the same time making listening evaluations (particularly level-matched listening comparisons) work to fine tune the results. And with full-range speaker evaluations in no way should the results indicate that a given item is the absolute best. Taste does play a part (this mainly involves radiation pattern issues, in my opinion), provided certain minimum standards for performance are met.

Howard Ferstler

Howard,

You've been on the front lines here. Wouldn't you say that the extremists are less influential than they once were? Of course, there are different schools of thought, and plenty of arguments. Yet, even the tweakiest companies seem to be acknowledging the importance of making basic objective measurements, while hardcore objectivists have added controlled listening to the measurement protocols. OK, the methodologies on both sides of the debate may be flawed, or too casual. The conceptual models are primitive. Still, the environment seems less hostile than it did 20 years ago, no? Is this wishful thinking?

-k

[kkantor]

Understand it? Certainly they are aware of it but understanding is another matter. I find I need to re-read most of the landmark papers every couple of years and still pull out new concepts or at least re-familiarize myself with them. Like you probably, I go all the way back to typing in Program Woof in Fortran, into a terminal, to have it spit out a crude response curve: marvelous stuff at the time.

In the last couple of years I've learned more about woofer/box science while trying to create high output very compact subwoofers. Certainly its the large signal, not the small signal issues that create the challenges.

The first step along that path was viewing the woofer and enclosure as a system rather than just assuming that "more magnet is good". The AR1 was one of the first steps there, but Jenson and RCA were in there too. (And don't make me prove that RCA invented the acoustic suspension system, imagine the flames!)

Second guess: is it Burl Ives?

David

Fair enough. I confess that just about everything I "invent" in the evening, I find the next day in some patent from 1915. Hunt's book might as well be titled, "The Dream Killer."

http://asa.aip.org/books/electro.html

What RCA work are you thinking of?

-k

PS- believe it or not, there's a small, bronze statue of a magnavox in downtown Napa, CA, commemorating Peter Jensen. Looks old and weathered. Not sure who thought to put it there.

[Zilch]

I think it's the Aussie TV guy, too.

[His initials are on my op system screen saver.... ]

[speaker dave]

Fair enough. I confess that just about everything I "invent" in the evening, I find the next day in some patent from 1915. Hunt's book might as well be titled, "The Dream Killer."

http://asa.aip.org/books/electro.html

What RCA work are you thinking of?

-k

PS- believe it or not, there's a small, bronze statue of a magnavox in downtown Napa, CA, commemorating Peter Jensen. Looks old and weathered. Not sure who thought to put it there.

H.F. Olson and J. Preston Vol 47, No.4 (of, I think Radio and Televison Eng., maybe SMPTE, just a partial photocopy), Oct 1946. In reference to a prototype LC1A and cabinet:

"It will be seen that the mechanical reactance caused by the air chamber behind the cone is three times the mechanical reactance resulting from the suspension system. Therefore, in the range where the compliances are the controlling mechanical reactances the compliance caused by the air chamber is the controlling compliance. (Hence a high alpha or Acoustic Suspension system, David). This expedient reduces the distortion caused by a nonlinearity of the suspension system."

This seems to both meet the definition of Acoustic Suspension and match its major claim. 1946 clearly preceeds Vilchur. I don't know if this was overlooked in the patent search, but I think it could have been put out as disqualifying.

It is very hard to invent anything new. Yes, Hunt and (Blumlein) have made it hard for the rest of us. I only have one patent and I know of a precedence that probably would have disqualified it.

I'll have to google jensen to see if there is a Napa connection. The first permanent magnet wine pit seperator?? Jensen obviously predates us, but I met Plach and Williams (Phil Williams at RDM for eons. Is he still alive?)

For the novices out there: Before Nevile Thiele of Thiele/Small fame there had been a lot of very thorough analysis of the woofer box system, both sealed and vented. Beranek, Plach and Williams, and Olson to name three. These were full of equivalent circuits and long equation solutions to them and a couple of graphed examples. Without computers to run simulations on it, it was only of academic interest. The beauty of Thiele's work was that he distilled it into a simple cookbook approach and said: "If you know fs, Vas and Qt we can define a box size and tuning that works. Don't even need to know the woofer size." (okay, he said it a little more elegantly than that!)

David

[Carlspeak]

David, your mention of Blumlein reminded me of his invention of the moving coil microphone.

It got me thinking about the whole microphone problem at the front end of the audio chain and it's inherent limitations of perfect recording.

I was wondering as to why no one has developed a microphone that mimics the ear's function, simulated cilia and all. Wouldn't that be a step towards solving the non-linear problems faced by current microphone technology?

[kkantor]

It may be less hostile than in the past simply because the industry as a whole is in trouble. Both tweak and mainstream magazines have folded, as have some pretty good companies, such as Dunlavy, Waveform, and NHT. Even top-tech recording outfits like Telarc, Dorian, and Gothic have folded. People are spending less, and so there is less of a concern with esoteric claptrap than with bang for buck results.

People tend to become surprisingly rational, at least when it comes to personal shopping and spending habits, during hard times. (Of course, as anyone who watches the news and the talk shows knows there is a lot of irrational behavior in other areas.) Audio becomes less important and even the fanatics have to cut corners.

Of course, with the "super" high end rational behavior is as ignored as ever. Go check:

http://www.calaudiotech.com/index.php

Click on the CAT MBX window to see some REALLY expensive gear, like speakers that range in price (each) from ten grand to a million bucks. I have no idea of the babes in the photos come with the speakers. At the prices they should.

If you want to watch a video that shows some of the hyperbole this company represents, go to:

http://uk.cinenow.com/videos/1590-californ...xpo-london-2008

There are several over the top videos on the above site that will offend just about anybody who has his head screwed on properly.

Oddly enough, the filthy rich are as big a group of spendthrifts as ever, since the company says that business is booming. The most satisfying thing about all of this is that most of those spendthrifts are not getting much bang for the buck at all. Most of them are suckers when it comes to audio.

Howard Ferstler

There will always be SOME fringe stuff around. The question is whether it dominates the mainstream debate. Let's analogize to a political environment... let's say the daily newspaper dialog is a bit more centrist than it has been in the past. Less talk of love-it-or-leave-it vs. overthrow-the-status-quo on the front page. That doesn't mean there aren't a bunch of NeoNutsie websites, or plenty of "every bite you swallow is killing a person in the third world" bloggers. Extremism will always exist, and have a market. CAT is no big deal to me, because they are so isolated. It's a market niche, not anything with any momentum. IMO.

BTW- Rocky times, for sure, but NHT is still chugging along after almost 23 years. I visited them not long ago.

-k

[kkantor]

H.F. Olson and J. Preston Vol 47, No.4 (of, I think Radio and Televison Eng., maybe SMPTE, just a partial photocopy), Oct 1946. In reference to a prototype LC1A and cabinet:

"It will be seen that the mechanical reactance caused by the air chamber behind the cone is three times the mechanical reactance resulting from the suspension system. Therefore, in the range where the compliances are the controlling mechanical reactances the compliance caused by the air chamber is the controlling compliance. (Hence a high alpha or Acoustic Suspension system, David). This expedient reduces the distortion caused by a nonlinearity of the suspension system."

This seems to both meet the definition of Acoustic Suspension and match its major claim. 1946 clearly preceeds Vilchur. I don't know if this was overlooked in the patent search, but I think it could have been put out as disqualifying.

It is very hard to invent anything new. Yes, Hunt and (Blumlein) have made it hard for the rest of us. I only have one patent and I know of a precedence that probably would have disqualified it.

I'll have to google jensen to see if there is a Napa connection. The first permanent magnet wine pit seperator?? Jensen obviously predates us, but I met Plach and Williams (Phil Williams at RDM for eons. Is he still alive?)

For the novices out there: Before Nevile Thiele of Thiele/Small fame there had been a lot of very thorough analysis of the woofer box system, both sealed and vented. Beranek, Plach and Williams, and Olson to name three. These were full of equivalent circuits and long equation solutions to them and a couple of graphed examples. Without computers to run simulations on it, it was only of academic interest. The beauty of Thiele's work was that he distilled it into a simple cookbook approach and said: "If you know fs, Vas and Qt we can define a box size and tuning that works. Don't even need to know the woofer size." (okay, he said it a little more elegantly than that!)

David

I'd say that quote pretty much nails it. I'll look around for it. Thanks!

Tom, etc, help me out here: I don't think EV got a patent on AS when all was said and done. Thus, KLH, Advent... and the rest is history.

In any event, IP law is a can of worm, patent or not. Probably better to have it than not, but its not as clean as I used to think. That's for another day, another thread. This one is already chock full of good, brain-hurting stuff, for me at least.

-k

PS- Peter Jensen lived in Napa after moving to the US. The reason I found out about the statue is that some of the Chicago Jensen guys would make a pilgrimage to it when the would visit NHT. (Only about 30 minutes away.) Of course, I suspect that Napa's famous wineries were a bit more of a motivation than nostalgia.

[speaker dave]

I'd say that quote pretty much nails it. I'll look around for it. Thanks!

Tom, etc, help me out here: I don't think EV got a patent on AS when all was said and done. Thus, KLH, Advent... and the rest is history.

Oops, full disclosure time...

I've re-read that section of the paper (I only have a partial copy starting near the quote) and it is clear that he is referencing the air chamber behind the cone tweeter. So RCA clearly invented the Acoustic Suspension Tweeter! I'm pretty sure this was from the SMPTE journal.

Another article by Olson and Preston: A New Line of Hi-Fi Speakers (Radio and Television News, Feb 1954) repeats the claim and this time is clearly in reference to the woofer: "The nonlinear distortion due to the suspension can be reduced to a negligible quantity by placing the fundamental resonant frequency of the loudspeaker at the lower limit of reproduction." The system has a cuttoff around 55 Hz with a woofer free air resonance stated as 30.

So letting the enclosure stiffness dominate the system had occured to Olson. Adding considerable mass and shrinking the box to less than 2 cubic feet had not.

David

[genek]

I'd say that quote pretty much nails it. I'll look around for it. Thanks!

Tom, etc, help me out here: I don't think EV got a patent on AS when all was said and done. Thus, KLH, Advent... and the rest is history.

History is loaded with examples of people who invented things and then either chose not to patent them or if they tried, did so incorrectly and had their patents invalidated. IIRC, Vilchur's patent on AS was invalidated, mostly because of errors resulting from his not using an attorney, and today nobody holds a valid patent on the technology. Subsequent to that, Vilchur chose not to try to patent his dome tweeter, and today nobody holds a patent on that, either.

Some friends of mine at the Xerox Palo Alto Research Center (PARC) used to have a digital counter on a wall that displayed a calculated estimate of the profits Xerox had lost over the years by not patenting many of the things originally developed at the center (the window/folder based GUI and the mouse being the most famous). The last time I visited there (about 10 years ago), the total was in the hundreds of billions of dollars.

If you ever get the opportunity to visit PARC, try to avoid being the first person to inject the word "patent" into any conversation unless you enjoy watching grownups cry.

[Carlspeak]

All this patent discussion reminds me of D'Appolito's MTM idea. He divulged it, to the best of my knowledge, in an early 80's issue of Speaker Builder. From then on it's in the public domain and, of course, the rest is history.

One of those 1/2 million dollar speakers at the CAT site has the MTM configuration.

[genek]

I believe that Villchur actually did get a patent (writing and researching himself to save money), but Electro-Voice contested it later on after they built a system that used the feature and did so without paying royalties to AR.

I think that was the error Villchur mentioned when he discussed his patent, that if he had hired the requisite patent people they could have conducted a more thorough search and found the EV prior art and he could have included language in his original application that showed how his work was not the same as theirs.

This was five years before Teledyne aquired AR. One wonders if Villchur hadn't already been thinking about getting out of the business at the time of the unpleasantness with EV

[kkantor]

History is loaded with examples of people who invented things and then either chose not to patent them or if they tried, did so incorrectly and had their patents invalidated. IIRC, Vilchur's patent on AS was invalidated, mostly because of errors resulting from his not using an attorney, and today nobody holds a valid patent on the technology. Subsequent to that, Vilchur chose not to try to patent his dome tweeter, and today nobody holds a patent on that, either.

Some friends of mine at the Xerox Palo Alto Research Center (PARC) used to have a digital counter on a wall that displayed a calculated estimate of the profits Xerox had lost over the years by not patenting many of the things originally developed at the center (the window/folder based GUI and the mouse being the most famous). The last time I visited there (about 10 years ago), the total was in the hundreds of billions of dollars.

If you ever get the opportunity to visit PARC, try to avoid being the first person to inject the word "patent" into any conversation unless you enjoy watching grownups cry.

No kidding!

A few years ago, I did some consulting work on a small corner of:

http://en.wikipedia.org/wiki/Alcatel-Lucent_v._Microsoft,

and got to attend a few days of the trial. Amazing stuff, this legal warfare!

-k

[kkantor]

"I reviewed some of the models that Jack designed, by the way, and they were quite good. "

Yes... my living room speakers are Classic Fours!

No doubt, the company was on the ropes, and has had to restructure substantially. It's a very difficult time to be in the speaker biz. Still, some of their products seem to be doing well enough to keep the brand alive.

"I find it patently offensive when people have enough money to waste it on stuff like this when the country is edging up against a depression."

Well, yes. Or that some of us can afford $500 speakers and laptop computers, when others are lucky to earn that in a month.

Oh wait, that's me. So, I guess it's ok then....

-k

[kkantor]

All this patent discussion reminds me of D'Appolito's MTM idea. He divulged it, to the best of my knowledge, in an early 80's issue of Speaker Builder. From then on it's in the public domain and, of course, the rest is history.

One of those 1/2 million dollar speakers at the CAT site has the MTM configuration.

D'Appolito's seminal paper on the subject specifies a particular crossover and geometric design. MTM's in general certainly existed long before it. It might have been the KEF 104.2 that re-popularized the approach, but I don't know who influenced who. Whom?

-k

[speaker dave]

Those used first-order networks, I think (he certainly used them with his later US Dunlavy line when he came back to this country), whereas d'Appolito required a fourth-order network with his approach, I also think.

If I remember right the essence of d'Appolito's paper was that an MTM would have minimal lobing if the center element and the outter elements crossover with 90 degree phase shift between them. Since you also have the variable of driver depth you can achieve 90 degree phase shift at crossover with a wide range of crossover slopes. I think Joe is a little embarrased that any symmetrical array now has his name attached to it.

We developed arrays at Snell and I had models with fairly constant vertical directivity for a number of octaves. I called it the XA series for eXpanding Array since the array length effectively expands in proportion to wavelength. (seemed like better marketing than shrinking array). The large XA Reference extended the array to the woofers as well (a 3 way). A waveguide on the tweeter gave the top two octaves the matching directivity.

Its kind of interesting that a fractal-like notion works here. If you can develop a scheme that works then that array of 3 units can become the central element of a larger array of 3 elements, and so on, and so on.

David

[Pete B]

I think that Dunlavy used expanded MTM arrays (MMTMM or WMTMW maybe) with the Duntech line when he was in Australia from 1981 to 1990. Those used first-order networks, I think (he certainly used them with his later US Dunlavy line when he came back to this country), whereas d'Appolito required a fourth-order network with his approach, I also think. Obviously, there would be considerably more overlap and phase issues with the Dunlavy alignment (Dunlavy promoted listening with the ears at tweeter height, and a ten-foot distance), and more power-handling limitations for tweeters and midrange drivers, too. The two Dunlavy models I reviewed actually worked quite well, however. The Allison IC-20 system I have been using for years uses double MTTM arrays on angled panels (with woofers at the cabinet bottom) and except for the first-order high pass for the midrange drivers, all filtering is second order.

Howard Ferstler

Generally, even order electro-acoustic XO's are in-phase at the crossover point and therefore

have symmetry in the polar pattern when properly designed. D'Appolito proposed the MTM

configuration to make odd ordered electro-acoustic XO's have a symmetric polar pattern. Indeed,

any network will provide a symmetric pattern when the driver layout has geometric symmetry as

with the MTM:

http://www.aes.org/e-lib/browse.cfm?elib=11762

The MTM configuration solves a problem with odd ordered networks, it does no harm with even

ordered networks. D'Appolito makes this clear in his abstract: "a simple geometric arrangements of

three drivers in a two-way loudspeaker is shown to eliminate lobing error independent of interdriver

phase relationships"

My brother (older) suggested this configuration to me when he was about 17 years old and I was

about 12, LOL! He didn't write a paper about it as he thought it was obvious. I had built my first 2-way

speaker, held it at arms length in front of me and noticed a change in output around the crossover

point as I rotated it. I noticed asymmetric lobing. He drew phase plots to figure out what was going

on and then suggested adding another driver. He even pointed out that in-phase networks did not

have asymmetric lobing.

[Pete B]

I think that was the error Villchur mentioned when he discussed his patent, that if he had hired the requisite patent people they could have conducted a more thorough search and found the EV prior art and he could have included language in his original application that showed how his work was not the same as theirs.

This was five years before Teledyne aquired AR. One wonders if Villchur hadn't already been thinking about getting out of the business at the time of the unpleasantness with EV

Here it is in Villchur's own words:

http://www.stereophile.com/interviews/105v...hur/index1.html

Professor Wadsworth ( http://dx.doi.org/10.1121/1.409268 )

at WPI where I studied loudspeaker design made a point of explaining

that a key feature claimed by Villchur was to have the driver suspension 10 times more

compliant than the air spring. This ratio is alpha in T&S theory; he was specifying an alpha

of 10. Wadsworth pointed out that only the very early designs came even close to an alpha

of 10 and that AR's own later designs were closer to 3. He pointed out that it was not practical

to manufacture such highly compliant suspensions. I did not review the patent at the time, or

ever since, but I did read Villchur's late 1950s AES paper were an alpha of 10 was mentioned.

His point was that an alpha of 10 is not required to provide reasonably low distortion. He also

pointed out that the large VC overhang was as, if not more, important.