Basically, a loudspeaker for the exercise robots would be nice, but dynamic speakers are too heavy to cost effectively move. Thus, a practical use for electrostatic speakers appeared. Electrostatic speakers are used in a Best Buy demo for a game. Typical for the age, there's very little online information on how to make an electrostatic speaker. There are no specific voltages or currents. The only fact is the driver part of an electrostatic speaker is much lighter than a dynamic speaker.

The only useful parts list is on:

http://jazzman-esl-page.blogspot.com/

There are no useful schematics, but notes on the speaker performance here:

http://sound.westhost.com/project1053.htm

The Elliott speaker uses the audio amplifier to power all 3 plates. The Jazzman speaker uses a separate supply for the diaphragm. They all passively power the stators by stepping up the audio amplifier voltage.

Presumably, the stators go at 1000V. The diaphragm goes at 2500V. The required power is unknown, though they say the speaker presents a 4uF load which requires a lot of power, maybe even more power than a bug zapper or cold cathode. The transformers are very large, but what if the audio amplifier could be actively stepped up by a semiconductor solution. It's unlikely a semiconductor solution would generate enough power, but it might work for a very small speaker.

Barring the electrostatic speaker, there's using some combination of piezo buzzers to obtain lower frequencies. Perhaps 2 piezo buzzers on opposite ends of a large resonator could alternate single pulses.

10 years ago, there was an effort to make a speaker which used any plastic surface as its resonator. It was targeted at eliminating speaker grilles in gadgets by using the enclosure itself. It went absolutely nowhere.

Send me a private message if you are interested in NOS vintage Electrostatic Speakers and parts.
Thanks!
-Josh