STAX SR-009 Open Back Electrostatic Earspeakers from Japan DIAPHRAGM (vibrating membrane): In addition very thinning!Sound unit of the new development has been mounted on the SR-009. Adopted a new ultra-thin polymer film material to the diaphragm that becomes the sounding body called super engineering plastic that was further performance of conventional engineering plastic. In particular, select an excellent material to "sound quality". From low to ultra-high range I have achieved a vast dynamic range and excellent frequency characteristics. Also new development elect load that plane drive the diaphragm full