ESL Headphone

[rendoman]

Hi all!
I'm trying to build a couple of electrostatic panels for headphone.
I'm reading a couple of books and opinions in internet about the right "rule" about size, polarization and materials.

I'm building frames for stators and diaphragm from 10mm PVC bar.
I'm not sure about type and thickness of diaphragm, normal film for food should be polietilene or pvc about 12 micron. Someone in audio forum tried 1 micron film with very short distance from dia to stators.

I tried first frame in thin lexan, but it wasn't good, too flexible!

Here a picture of Esl operation





Here the good frames in PVC





Here the bad old frame, I made a wrong choice with the not perfect wooden plank

[Tuomas]

That's interesting project!

[rendoman]

Thank you!!

Test frame for Esl is almost finished. I modify a little the spacers, now they are 1mm. Thinking afterwards, I would not have made the holes near diaphragm, but you always think about it later.... Not a perfect job, but still usable.
It's time to model 316 stators and connections!

[rendoman]

I just cut and ground a couple of 316 steel for stators. Unluckily I'm not able to weld connection without specific flux for oxi-acetylene torch, it's impossibile to use old ac trasformer welder at low current, I will go for mechanical connection for test with some plastic clamps and nylon screws. Next : diaphragm connection

[rendoman]

Just finished locks for stators, connection for diaphragm will be a large copper, brass or aluminum plate or tape.
I'm trying to understand if contact glue for leather is good also for pvc (120 grit sand paper). At first sight the dried glue is not easy to remove with blade from pvc, I will try!

[rendoman]

Just arrived Used (as new) old Stax electret adaptor. Basically a couple of high ratio transformer (x10) inside a box with a couple of limiters. The limit seems to be for 50v imput 500v output (peak-peak), close to perfection to drive stators with enough swing.
I tried glueing mylar to pvc with contact glue... I broke 2 times the mylar 3 micron and 3 times the 6um. It's a bastard job, I don't know how much tension is correct, books teach 1-2%, but it's not easy to Mount by hand. If the prototype will be good I will made a good stretch jig in order to replicate the correct tension.
Now it's time for coating diaphragm and making the Hv bias power supply

[rendoman]

Safety first! Wear condom!
A very big Domopak in order to protect from dust the new ESL panel. To be honest, it's not so well made and finished, but it's the first try! I made mistakes for sure so I hope to make a better job next time. I don't know the Fs of diaphragm, I didn't check, I stretched the mylar with hands and I'm very curious to know if it will sound... or it will explode .
Tomorrow, if I'll find all parts, I'll build the High voltage bias unit.

[rendoman]

It's alive! And pretty good sounding, above all it's the first prototype!

[rendoman]

Merry Xmas!
I just tried medium bias, more or less 1,2kv, results are quite good in my opinion, I have to make some serious measurement, the spl is increased. I also got some trouble with saturation of transformer core, I will connect soon the 2 transformer in series. Above all this panel needs about 5\600v p-p for high spl (not necessary for headset).

[rendoman]

Pretty nice result as first panel!
Next change the tension and thickness of mylar, discovering bass range. I will build soon a couple of panel only for headphone, with right size and well tuned.