February 15th, 2006
Electrostatic headphones differ from normal headphones in that they use high voltage, exhibit far lower distortion, and can be built at home fairly easily. This is my account of building a pair of electrostatic headphones from scratch.
I first thought electrostatic headphones were a joke. It didn’t sound safe to strap high voltage transducers to your head. But after my work with electrostatic loudspeakers I had the skill and knowledge to try building a pair and listening to them.
Basically an electrostatic headphone works just like an electrostatic loudspeaker, of course on a smaller scale. It modulates a diaphragm using electrostatic force, rather than electromagnetic force as in conventional speakers. They are usually a charged sheet of plastic film suspended between two conductive sheets called stators. The stators are ideally acoustically transparent but in reality are perforated metal.
Rather than build a pair from scratch, I decided to modify an existing pair of dynamic headphones to be electrostatic. A look around the house yielded the perfect candidates – an OLD pair of headphones, and they are of the 1970′s bulky construction, like half a ‘barrel’ for each ear. Not pretty to look at, but a lot easier to retrofit with electrostatic panels than the modern curvy compact ones.
Unbelievably, the first prototype I built needed nothing more than mylar to get working, all other parts were adapted from the headphones. The headphones already had thin perforated metal grills crimped around the 95mm circular driver. There were also circles of card 0.5mm thick. So I used these parts along with mylar to make a monophonic earphone! Once I got that working I set to work making a proper stereo pair.
Here is an exploded view of what the panels are like, please note it is not to scale, the holes are actually only 1.5mm in diameter.
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