I already told you about my electrostatic headphones in previous post and now it’s time to look at another very interesting headphones from Stax that was made roughly at the same time. SR-40 is not an electrostatic headphones but “electret” ones. It’s very similar to electrostatics, only membrane there is thicker and already hold an electric charge to react in static field. With precharged membrane there is no need for addition electricity circuit just for build up a static charge, so it helps to reduce production cost. Beside it, electret technology considered inferior to electrostatics. Actually, all those electret headphones from Stax are dirt-cheap compared to more elaborate electrostatics and you can get them from Ebay for mere 50$-100$. So I decided that it’s not too expensive and have got one for myself.
This piece of fine audio equipment is electrostatic headphones that was made back in 1970-s by Stax company in Japan. Electrostatic headphones use completely different technology to produce sound than conventional headphones. Instead of electric coil glued to sound cone that moves in magnetic field, they use static electricity to move charged membrane of few micron thick between two perforated electrodes. So there is no magnetic field, only static electricity. You can read many additional info here. Stax invented the technology back in 1950-s and produced first electrostatic headphones in 1960 and till now they continue to make them. Stax new top model SR-009 that came out in 2011 cost around 5000$. But headphones from 1960 is still available through Ebay where you can get them for couple hundreds. I actually did just that and now lets look what I have got.