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Williams Audio 3rd October 2005 08:05 PM

acoustat diaphragm
who knows about acoustat esl:
1- what is the thickness of the diaphragm of acoustat 2+2?
2- the units can be repaired diy kits, any body did it before?
3- how the unit is built, is it glued ?
4- changing the diaphragm to a thinner one say, 6microns will do any better?
best regards

SY 3rd October 2005 08:18 PM

It appears to be 1/4 mil (10 micron) Mylar coated with a carbon-loaded paint. The panels are glued together and can be quite a challenge to get apart. I used an ultrasonic blade cutter, but that's a pretty exotic tool.

moray james 4th October 2005 12:48 AM

2+2 diaphragms
The Acoustat uses a DuPont HS65 diaphragm. This is a 65 guage diaphragm and is a shrink form of biaxially oriented Mylar. The coating was improved at some point but is a whitches brew of carbon the composition of which I believe that Acoustat never knew (as it was purchased as a finished product). I think that there are better materials available which will weigh far less and have far higher surface resistivity.
The panels are assembled with a mixture of styrene and methelyne chloride so it is a solvent weld. I have rebuilt them but it is in my opinion not worth the effort. For about the same amount of work you can construct new and superior panels from scratch. Old panels tend to show breakdown of the PVC diecectric and so even if rebuilt will arc. If you do decide to rebuild your panels I would suggest a though solvent scrub of the stator wires followed by 3-4 wet coats of spray PVC primer paint available at auto shops for plastic bumpers. You only need coat the inside of the stator wires. This will patch up any small holes that get punched through the insulation and leave carbon tracks. Not something that I would ever choose to waste the time on again. Further the styrene louvre has tons of plasticizer in it and over time that sweats out of the plastic leaving the louvre very brittle. Acrylic is far better but much more expensive. You can also build with 3/8's inch thick louvre (in either material) and you can expect a life of 15-20 years with styrene and considerably longer with acrylic. If the panels are handled gently you can probably tack on another 5-10 years.
6 micron film will yield better high frequency performance but I don't think that going thinner would be a good idea. As has been discouvered by Sheldon stokes you may end up hearing high frequency crap out of your transformers that you don't want to know is there and that the higher mass diaphragm rolled off. So a small blessing in disguise. A dedicated super tweeter made from ultra low mass film with its own transformer is probably a much better way to go.
I-Forgot has a superbly simple stretching jig if you go to a non shrink film. C grade films (capacitor grade) are the best kind (I believe) for diaphragm service.
I have some genuine HS65 film if you are interested you can PM me. Hope this helps best regards Moray James.

Williams Audio 4th October 2005 06:03 AM

acoustat diaphragm
Hi moray james,
Thanks you for such a detailed explanation, it is very helpful.
I don't think i will repair it back too much chemistry stuff.
But I do take your advice and will try to build a set from scratch.
Do you know about some good books and articles that will help ?
Best regards

moray james 4th October 2005 06:54 AM

look here
Williams: you can have a look at the archives at this diyaudio site as there is much valuable information. You can also look here and you will find all the useful information that I can give you along with lists of all the related sites that I have found on line. I hope that this helps. I would say that all you have to do is to ask for assistance when you need it and you will find someone who can share what they know. There are also sites where yo will find full ESL kits if you like too. Have fun and keep us all posted as to the results of your project. I look forward to hearing the whole story. You might consider rebuilding at least one of your existing panels that does not work so well. You can use it as a trial run on the building of your new panels. You don't have anything to loose as the panel is pretty much a loss anyway so you can't make it worse. Best regards Moray James.

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