Looking at a vintage electret headphone? Tempted to buy a vintage one? There are a couple things you should know before buying anything that says “Electret” on it!
Vintage headphones are a cool thing to have, and lately I found a really cheap one, boxed with amplifier. It looked cool, and soon after the seller said I won and I had a couple hours to wait before his shift was over.
So in the meantime I looked up and asked around what I could expect. Nothing to find of the device itself. A Japan Piezo Co Ltd. model ESR-2.
Too good to be true for cheap?
There are a couple things that stood out from the discussion that followed.
- Capacitors:
For one, such an old device with voltages ranging from 130 to 800V at peak would for sure use fairly special/high rated capacitors. There would be a high change they would have gone bad, might explode upon plugging the device in or just poof up in smoke. - The membrane:
Due to the nature of these headphones, the inner plate can age badly. It is mostly made out of Mylar in the most common headphones, The moving plates (Mylar + wires) can dry out and get stiff, making the sound production horrible, soft or just barely make any noise whatsover. The point of the plate is to move freely, creating sound in the process in between two conducting plates. These plates are connected to the little amplfier box that comes with the headphone.
So, electret headphones are charged on the outer two plates, moving the inner Mylar substrate. Resulting that rather then having the middle plate charged as well, which is what electrostats do. See electret as a cheaper variant of the electrostat.
Conclusion:
So as you’ve now read in the list above, it might look really good but it’s mostly too good to be true!
The headphone was listed for a good week now in a fairly big HiFi group. No one even bid on it!
Turns out there was a good reason not to.
Buyer beware! Electret is NOT the same as Electrostatic. Especially vintage models!