I believe metalized membrane is no longer used since the '50s due to severe limitations. Common practical ESL design operates by principle of Constant Charge (on the membrane with low conductivity coating in the middle), the front and back stators are modulated push-pull by audio. See illustration on P3 of Steve's DIY ESL - An Overview of Electrostatic Speakers.pdf.
He was human... you used past tense, has he passed?
Controlling surface charge on a very good film is always a problem. A design which does not do that could be an issue, perhaps what Richard perceived.
Hans said 10e+6 megohms...was that a typo and not meant to be 10e+12 ohms. I wouldn't have any idea how to measure that high a surface resistivity. My experience is measurement of resistivity of sputtered titanium at the single digit ohms per square level (the correct way to specify surface resistivity) on the other side of 1/4 inch thick alumina, using (believe it or not), a 10 turn coil at 1Mhz measuring Ls/Rs..
I think the MLI we use is double side sputtered alumina over 2 micron mylar for infrared reflection, I'd have to check on that though.
jn
Nice link, thanks.
I note he mentions near field falloff is minimal also.
I didn't see mention of how the rotor is uniformly charged, as in any coating on one or both sides.
jn
Peter Walker died in 2003 at the age of 87 - long gone but his speaker lives on.
I can’t think of any reason why a dual coating should be applied.
Not one single of the several very detailed AES document that I know on the subject have suggested this.
Like you said, take into account the air gap width of 2.5 mm and it will be clear that the thickness of 3u polyester foil plays no role.
Absolutely right, I fully agree.
Up until now, nobody has been able or even dared to change the least to his original design from 40 years ago.
Not many active in audio business can make that claim .
Hans
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But is the martin logan approach of a curved stator a better way of doing it? I had a pair of aerius for demo once and did like them a lot.
You have to see the designs of the Quad stuff like the original 404 (I think that was pre-current dumping) in the context of what was going on at the time (late 60’s early 70’s).
You look at a Locanthi’s stuff from 1967 and most today will cringe. But, given very expensive semi’s, construction techniques still stuck in the tube age and you have a bit more sympathy for the guys who built remarkably good stuff on the ‘smell of an oil rag’.
I have a 50 year old Pioneer receiver I am working on (restoration project) and the circuitry is abysmal but it’s apiece of history. Still works BTW but the pots crackle like hell!
Would I hire Locanthi or Walker to design a modern power amp? No, because although they were trailblazers, it took another 25 or 30 years for all the knowledge across numerous aspects of amplifier design to be collated into one or two places (most famously Self and Cordell) that a modern practitioner can go to. Someone having read those books and interacted on a forum like this for a decade or two probably has a better handle on what to do thanks to the knowledge shared by others.
🙂
O.K. thank you.
It looks rather damped room, just like my current study.
Is this also where he makes the FR recordings of louspeakers ?
Hans
You might check B&K's site for constant charge vs constant voltage operation of an electrostatic transducer. They have a very nice derivation of the implications with respect to distortion.
Measuring at 1 meter distance with little room interference gives a nice idea how well a LS is designed.
The ESL63 scores splendidly as your and my measurements have shown.
However, you are listening further away at your listening position.
So the question is, what is more important, near field or far field.
It seems that the ESL's are quite susceptible on the acoustics of the listening room.
On the other hand, they do not sound dull at all in my case with -12dB at 20 kHz.
Maybe I should give a DSP generated correction file a try to see what it changes to the perceived sound.
But it seems quite obvious that Stereophile is not making near field recordings, I don't know if that's a bad thing.
Hans
A most interesting read about P. J. Walker, by G. A. Briggs, no less.
Revisie klassieke Quad apparatuur
That is why you fail..
My apologies, just had to say that..I think it was Yoda who said that...
A really good insulator allows charge to remain in place. Anything that can put charge on the surface, the surface will retain a potential. This is why insulating surfaces are coated prior to viewing in a SEM, as the image will very quickly defocus when the ebeam hits it.
Perhaps a single coat to get past the patent?
In general, those working the regime between ten kilovolts and 10 megavolts rarely do research with AES papers. Our bar is significantly... well you know the drill.
As I continue to repeat....fundamentals, ya gotta know the fundamentals.
Anyone who continues to consider a 3D world in a one D thinking is going to miss things. Think surface charge mobility, lateral charge velocity (zero, btw..)
Don't be silly. You confuse ability with desire.
It's shocking nobody has done anything given the absolutely huge amount of money to be made making five or ten speakers a year...by improving a parameter that only two owners I am aware of noticed are dependent on line voltage. (Very highly technically knowledgeable owners I might add).
jn
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According to this source, which also quotes GB Pat. 815,978 the diaphragm was coated on both sides:
The Quad ESL - FAQs
The Quad ESL - Nylon .vs. Graphite
People have been reporting that their hifi sounds better late at night when the voltage is usually at its highest for 40+ years. Of course this has never been correlated in any way. Personally I reckon its as much to do with being relaxed and a lower noise floor in the environment.
Second link worked for me. very nice. Btw, who wrote that?
I note this blurb:.
Also, he does talk about 10e+12 ohms per square, and mentions the difficulty in measuring higher..well, no kidding. whoa. I wonder if they have to use a controlled environment to measure that high..
jn
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A curved stator disperses the sound in the horizontal plane.
The ESL63 disperses equally in all directions.
Hard to tell what is better, but I would say the more it approaches a point source the better, but only listening to the different solutions will tell what you prefer.
Fact is that no electrostatic speaker is as much praised as the ESL63.
Hans
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