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In Reply to: Re: Much simpler answer posted by andy19191 on February 27, 2007 at 03:54:40:
Your original question is meaningless, because there is no such definition as 'neutral audio'. How do you measure that?
Personally, I can measure to 1 million to one, with THD and IM distortion. This appears to be about 10 times better than 'Stereophile' typically measures. This is about -120db. I also can separate individual harmonics and noise from the measurement, and accurately measure harmonics to 100KHz. There is even newer and better test equipment out there, but I cannot personally afford it. However I doubt that an even lower measurement would gain much. After all, sooner or later, an extremely low value in distortion, by itself, must be meaningless, even to the 'objectives' of this world.
I will give an example however of how I once changed the sound of a power amplifier that even surprised me.
It was 1973, and I was hanging out at Mark Levinson's house. We were making a new phono pre-preamp together, to be called the JC-1, and Mark also made some discrete line level modules for the Grateful Dead, for use in their new sound system.
Mark had retired his Marantz 9 tube power amps and bought a Phase Linear 700 power amp that went well with his new DW electrostatic loudspeakers.
Both Mark and I thought this combination pretty good, and well balanced. However, Mark's mother (did I mention that Mark lived with his family?) complained that the new setup hurt her ears, so Mark and I discussed the problem.
I told Mark: "We could change the bias and cut out the protection circuitry."
I knew that the Phase Linear 700 ran next to empty in bias, because I could just put my hand on a heatsink after some time in idle and it would be just barely perceptably warm over the ambient.
Well, we did what I suggested on his workbench. The bias was slightly increased to reduce the xover distortion to where I could just feel a slight difference in the heatsink temperature. (you must remember that by 1973, xover distortion had been proven to be inaudible in DB tests) and the protection circuits were snipped out.
Well what happened? After we got the unit running again, Mark asked me: "Where did the highs go! Did you change something that would affect the frequency response? " I said: "No, Mark, I just removed some of the xover distortion in the amp.
Well, the next time I came to visit, Mark had an electrostatic tweeter mounted on top of his big electrostatic speakers. Subsequently, the electrostatic speaker came out with a MK2 version with a piezo tweeter (ick) on top. Apparently, the electrostatic speaker manufacturer had exaggerated the actual high frequency performance of his speaker in his literature, but this was originally taken care of by the addition of higher order harmonics from the bigger amps that were necessary to drive the speaker properly.
So much for the inaudibility of xover distortion.
Now I want to ask you engineers out there: Why do Motorola piezoelectric tweeters sound the way that they do? What can I MEASURE to show how they sound, and why doesn't everyone use them?
Follow Ups:
Thanks for the length of the reply but you still seem to have avoided directly answering the question can you measure what you are reporting hearing. Nonetheless, the gist of your response would seem to be that you cannot measure what you are reporting hearing. Is this fair?
I remember the Dayton-Wrights well having heard Dr. John W. Cooledge's pair back in '76. While his MK Is were a tad shy on the top, I was taken by their incredible coherency and low level resolution capabilities. Thirty years later, I'm still a 'stat freak.Indeed the later MK II / MK III's were a mixed bag (no pun intended - remember the outer diaphragm used to contain the SF2 gas?). More efficient, somewhat more reliable, but had that damn tweeter. I worked for a dealer who picked up the line at the time of the MK IIIs. He drove them first with a Dunlap-Clarke amp (Dan D'Agostino was the rep for both D-W and D-C at the time) and later with Nelson Pass' first effort, the 800A and finally a Stasis 2. Some folks disconnected the piezo. The store used an identical driver for use as a - burglar alarm!
SF6 gas :)
rw
Well, I am a chemist :)
it bears repeating. Dr. Cooledge not only wrote for TAS from day one, but he has been a member of the Atlanta Symphony Chorus for about thirty years as a baritone. One of the Dayton-Wright panels required replacement. He had to first cut the outer diaphragm to gain access to the interior where the panels are located. After replacing the panel and resealing the outer diaphragm, he had to replace the SF6 gas. So...As you know as a chemist, SF6 is heavier than air. Exactly the opposite of helium in that regard. You can put it in a cup where it remains colorless, but you can feel it. JWC inhaled a bit and then sung a line from an opera. It sounded like Lurch at the Met! That was hilarious. :)
Cool! I have heard that people have tried that before but personally I have never played with SF6. I am glad most electrostats don't need it. I guess the panels were moisture sensitive or did it simply reduce the chance of arcing?
Electrical insulator to prevent arcing.
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