HI
Thought you guys may be interested in this step by step build of a very large curved ESL
Building an Electrostatic Speaker
Andy
Thought you guys may be interested in this step by step build of a very large curved ESL
Building an Electrostatic Speaker
Andy
I am actually the builder of this stat and the starter of the thread you mentioned. I built my first one more than 25 years ago (it's the large blue one that you can see it some of the pictures) and have recently been showing a smaller one at the Lone Star Audio Fest.
I do builds on spec but don't see a need to keep any secrets, I am willing to share all of my 'secrets' with anyone who wants to hear.
I do builds on spec but don't see a need to keep any secrets, I am willing to share all of my 'secrets' with anyone who wants to hear.
Hi,
I'm continually amazed by the ingenuity and workmanship of the DIY community and your project is exceptional. I can't wait to see the finished speakers-- any details of the build you care to share with us will be greatly appreciated. Have a great day!
Charlie
Savannah, GA
Hello beun,
Your web page makes mention of using low resistance metalized diaphragms. Do you drive the diaphragms directly from the transformer like Beveridge and Final did? Or do you use a more conventional setup where the stators are driven by the transformers and the diaphragm is connected to the HV supply through a large value resistor.
The reason I ask, is that both Final and Beveridge had problems with the metalized coating being eaten away over time. Have you experienced any such problems?
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Bolserst,
The setup is conventional, the membrane is connected through a high valued resistor (100Meg) and the stators are driven by the transformer. The oldest speaker was still playing fine after more than 20 years in service. Some small holes did appear in the metalization (not the membrane itself) which is caused by burning off dust and small gnats over time. The total metal area lost was less than 1% which does not effect the sensitivity in any way.
The setup is conventional, the membrane is connected through a high valued resistor (100Meg) and the stators are driven by the transformer. The oldest speaker was still playing fine after more than 20 years in service. Some small holes did appear in the metalization (not the membrane itself) which is caused by burning off dust and small gnats over time. The total metal area lost was less than 1% which does not effect the sensitivity in any way.
That's good to hear.
I had always assumed it was the high AC current allowed by the capacitors bypassing the HV supply and high valued resistor in the Final and Beveridge designs that led to this problem.
I think 20 years of service proves the effectiveness of the 100Meg resistor for keeping the diaphragm current low, even during overload conditions.
Aluminum Coating on Diaphragm
Bolserst,
Audiostatic also had problems with the aluminum coating leaving the diaphragm on their ESLs a few years back. They used about +5kV on the diaphragm through 10.5M resistance.
A colleague of mine has suggested this is caused by ionization (ozone) in the gap and Aluminum having a valence of +2 being pulled to the negatively-charged stator. If so, making the diaphragm negative with respect to the stator should help. Reducing the field strength would also help.
Bolserst,
Audiostatic also had problems with the aluminum coating leaving the diaphragm on their ESLs a few years back. They used about +5kV on the diaphragm through 10.5M resistance.
A colleague of mine has suggested this is caused by ionization (ozone) in the gap and Aluminum having a valence of +2 being pulled to the negatively-charged stator. If so, making the diaphragm negative with respect to the stator should help. Reducing the field strength would also help.
Huh. Interesting. I have worked on some Audiostatics that had degraded coatings.
However, all the Audiostatics I have seen used a high resistance coating on the diaphragm, not aluminum.
Do you know what models were involved?
Here is a link where a seller describes repair of his failed units he offers for sale:
Marktplaats.nl > Audio Static ES-50 (Hybryde) - Audio, Tv en Foto - Professionele Audio-, Tv- en Video-apparatuur
"The original Diaphragms Were one half mil metalized mylar Which were very conductive. Were Purchased this pair of speakers very cheaply becauses one panel was bad. Both panels Were disassembled and the metalized Diaphragms Replaced with one half mil mylar coated with an Indium Tin Oxide coating or much higher Resistivity."
Thanks!
Just noticed the description seems to be a cut and paste job straight from Sheldon's website.
Audio-Static ES-50
You're right!
I also found an ES-100 repair project that "references" Sheldon's ES-50 repair: Audiostatic ES100 - Reperatur und Modifikation -
This past weekend I swapped a few emails with Sheldon to try and confirm whether or not Audiostatic had used metalized film in the ES-50.
According to Sheldon the film was not actually metalized or shiny. But, it did look to him like some sort of vapor deposited coating. This was early on in his ESL repair career, so he did not have any way of measuring the resistance. He plans to update his website at sometime to more accurately describe the diaphragm and coating.
Acoustat Spectra 6600 modified J.J.
All steel frame covered mahogany wood
weight 600 pounds.
All steel frame covered mahogany wood
weight 600 pounds.
An externally hosted image should be here but it was not working when we last tested it.
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