Friday, February 4, 2011

Acoustat and other electrostatic speakers

I've come across an interesting discussion oriented around building replacement or improved versions of the Acoustat panels:

Here's a short description of the Acoustat design: wire stators with milspec PVC coated wire (this was determined to be better than more resistive insulators such as Teflon, read Jim Strickland's white paper), 1/2 inch styrene louver frame, HS65 mylar membrane coated with a somewhat less-resistive-than-usual coating, felt damping in back

The HS65 material is actually heat shrink, shrunk into correct tension.  It tends to expand around tension points over time, but can be re-shrunk with blow dryier.

HS65 is far thicker than the usual membrane material, 0.00065 inch or 0.65 mil or 16.5 micrometer
Martin Logan uses 0.5 mil or 12 micrometer membranes (a bit thinner)
Quad uses 0.13 mil or 3 micrometer.  (Many electrostats are in the 3-6 micrometer range.)

Thus the Quad membrane is less than 1/5 the thickness.  Many people think that thinner membrane yields greater transparency.

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