for a full sized animation and a description of how ESL's work
ELECTROSTATIC LOUDSPEAKERS
We'll be referring to electrostatic speakers as ESL's. Stats are a nice shorthand for them, as well, similar to saying dynamics for cone speakers.
Quick comparison between dynamics and stats:
1) Stats use electrostatic force to vibrate a nearly weightless membrane. Dynamics use electromagnetic force to vibrate a cone.
2) The force on a stat's membrane is spread out evenly, so the membrane moves as one. Cones are pushed from the middle and vibrate in ways other than the ideal in-out motion.
3) The force on a stat's membrane is simply proportional to the voltage at all times, so linearity and low distortion occur naturally. The position of a cone, however, is a complex function of current plus half a dozen continually changing parameters, making linearity and low distortion impossible under typical operating conditions.
4) A stat's membrane is as thin as a twentieth of a sheet of paper, far lighter than the air it is vibrating against, so very little power is used to vibrate it. A cone and its driver coil are at least 100 times as heavy and sprung by a spider and surround, so most of the power goes to move all that.