Reading Patrick Turner in
. au:

There is a chance the membranes are being pulled off centre but without
being
pulled right over against a stator so that might explain the buzzes.

Aha!

There was talk earlier of the sensibility, even necessity, of coating the
membrane on both sides. IIRC you dismissed the idea, at least to having any
effect, and further wrote of practical difficulties in this particular case.

Yet it occurs to me thinking of it that it must make a difference.

In the double coated case each side of the membrane each side sees an ideal
equal distance to each stator, with a dielectric of air.

In your single side coated case, one side sees its distance to stator with air
dielectric, and the other side sees that distance + the membrane thckness,
with a mixed dielectric of air and the membrane. The mylar will increase the
capacitance, and the distance increase decrease it; by less, I imagine ...

Then there's the slightly unequal by mylar thickness electrostatic forces.

Did the stiction always occur just on one side? Which? Coated or uncoated?

I dreamed of maybe one day building an ESL pair some while back, and trawled
around the DIY circuits and sites of the time. Now I seem to have accumulated
large ex elegant office tall wide wooden doors for large smooth work surfaces,
and a couple of roll ends of what looks like possibly useful diaphragm film,
and an old Tanner table saw for frames (and dynamic speaker boxes), so perhaps
I will sometime still do so; everything in me (and perhaps being a Libran
influences this wants to see the film coated on both sides, for symmetry.

How much these potential distance effects may matter, one should at least, if
unable to test, fully consider, do you not think? Theorise, discuss, etc?

Then again, it occurs to me - in a sense, with two coatings, effective, one
each side, not only do we get symmetry, but maybe double the charge capacity?

Plus the very sandwich itself has two equal sign charges either side of a
dieletric, the whole central. I intuit that this is far better than one-sided.

I am sure others here may have more understandings and competence in these
fields ahem than I evidence in these rambling thoughts ... let's hope so!

Regards,

Ross Matheson
Auckland, NZ.