My diy headphones are not electrostatic but I do have electrostatic Stax 404s and have listened to Staxs for years,
the high voltages have never worried me...the stax use about
600v polarising rather than the 2kv suggested.
Commercial ones are presumably designed and tested to be safe
but I think this is an important issue for DIY phones. However,
I also think it is easy to fix. Just add a grounded metal grid
closest to the ear. That should prevent potential hazards (as
long as the grounding is not faulty, that is). Alternatively, you
could probably make the design of the phones and amp s.t.
the electrode on the ear side is always grounded.
This is a picture of my transducer.
I only have one set of parts at the moment [I will have a pair when the rest of the parts arrive] ,the diaphragm is a reject one
I just installed for a test so ignore the dodgy folding.
I like the idea of using a pair of 100mm dual cone car speakers I have lying around doing nothing. The very low drive level compared with their 20 watt power rating should make for reasonably low distortion. Given the weight, you could only probably use them laying down, or perhaps have shoulder supports! If the coupling to your ears is good it would have to produce great bass. Just watch the sound level though!