• Aluminum foil used as a transducer

I would have guessed that an electromagnetic planar speaker would be made with a non-conductive membrane having a conductive foil etched onto it that acted like a voice coil. This would be surounded on both sides with a perforated magnetic panel. Seems like an electrostatic planar would have a non-conductive membrane surrounded on both sides with perforated plates that are charged to high voltage.

So I guess I'm missing something, because I'm not seeing how a homogenous conductor can be used for a membrane. I never thought it through, but on first glance, it seems like you'd need something more like wax paper or plastic wrap.