After some experimentation, we ran them on an impedance analyser, and got this god-aweful plot that peaks around 170 ohms at 700hz, and drops to less than .4 ohms around 20khz. The phase shift swings more than 70 deg around 20 hz, and -80 deg around 5khz. This is dangerous to our amps, so we're looking for methods of cleaning up the complex impedance that the amp (or crossover) sees.

For those unfamiliar, the electrostatic speaker consists of a stepup transformer, and two parallel plates with a charged membrane suspended between them. The amp plugs into the the transformer, the transformer powers the plates, and the membrane gets pulled back and forth. So the impedance the amp sees is some combination of capacitive and inductive impedance.

SPICE seems to have trouble realistically representing a transformer, so my efforts of computer modeling the system have hit a roadblock. If anyone can provide some assistance in this aspect, that'd be great. . .

I'd heard mention of a Zobel network for smoothing inductive impedance for regular magnetic coil speakers. I was wondering if a similar configuration would work for the ESLs. RIght now, we've just got a big, honker 2ohm power resistor in series with the transformer on the amplifier side, so that helps boost the resistance a bit (though of course we're dissipating a lot of wasted power as heat). But that doesn't help with the wild phase shift swings, which could induce all kinds of crazy destructive oscillations in our amps. If anyone could give me some help, or point me in the right direction, it'd be most appreciated. Thanks.