Building an Electrostatic Speaker

[Atom66]

HI
Thought you guys may be interested in this step by step build of a very large curved ESL

Building an Electrostatic Speaker

Andy

[geraldfryjr]

Originally Posted by Atom66

HI
Thought you guys may be interested in this step by step build of a very large curved ESL

Building an Electrostatic Speaker

Andy

Very cool link!
I will follow this. jer

[beun]

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.

[CharlieM]

Originally Posted by beun

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.

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

[beun]

Charlie,

All details of the built will be laid out in the thread, if you or anyone else would like to hear additional information that is not mentioned of asked in the original thread, I will be more than willing to answer it here.

[bolserst]

Originally Posted by beun

...if you or anyone else would like to hear additional information that is not mentioned of asked in the original thread, I will be more than willing to answer it here.

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?

[beun]

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.

[bolserst]

Originally Posted by beun

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.

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.

[Mike Beck]

Originally Posted by bolserst

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.

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]

Originally Posted by Mike Beck

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?