I think electrostatic headphones are the best headphones for classical music. It's that simple. This is because they reproduce the sound of orchestral music extremely accurately, with hardly any distortion or coloration of the sound.
In fact, I believe that they can provide an even better listening experience than full-sized electrostatic speakers!
Why are they so good? Why doesn't everybody have them?
Like most things in life, electrostatic headphones are a mixed bag of compromises. The important thing to realize is that their advantages are all to do with the sound you hear. Great!
Their disadvantages are the result of how that exhilarating sound is produced:
The electrostatic driver inside each headphone earpiece is like a flat sandwich. It has 3 layers.
The "bread" on the outside of the sandwich is 2 thin, flat metal mesh plates with lots of holes. These 2 mesh plates must have enough perforations to allow air to flow easily through them. This is also called "acoustically transparent".
The "meat in the sandwich" is a thin film of mylar or plastic. And I mean thin - less than 2 micrometers!
The secret is the film. Compared to electromagnetic driver cones in conventional headphones, the electrostatic film has these advantages:
There is a very small gap between each side of the mylar film and the metal mesh plates, to allow the film to vibrate.
The thin mylar film is coated with a fine layer of something like graphite, which conducts electricity.
When in use, this coated film is charged up with a constant voltage, usually several hundred volts! This is a static negative charge which remains constant, and is where the name "electrostatic" comes from. It's like the static you can get on a sweater, but much more powerful.
The two thin metal mesh plates that form the "bread" of the sandwich take the positive electrical signals from the amplifier. These signals go up and down depending on what the music is doing.
(Warning - technical bit!) The two metal plates receive their electrical signals 180 degrees out of phase. This means that when a signal comes down the wire, the mylar film is attracted towards one metal plate, and repelled away from the other metal plate, with equal force.
As the strength of the positive electrical impulses go up and down, the negatively charged mylar film is repelled and attracted, causing it to vibrate. As it vibrates it moves the air around it, making sound!
Because the electrostatic forces on the film are equal across the entire surface of the film, it remains totally flat as it moves. Conventional speaker drivers distort as they move, altering the sound.
Because the statically charged film is so thin and so light, it responds the merest whisper of electric voltage variation. The movement of the film is as close to instant as makes no difference.
When that drum stroke stops, the film stops instantly, too, because it has virtually no weight and so no momentum. There is NO time lag between the audio signal coming down the wires from the amplifier and the movement of the film.
As I said at the top, I believe that electrostatic headphones are arguably even better than electrostatic speakers, because the sound generated out of the back of the film in the headphone is directed away from your ear into the air around you.
In a speaker, the sound coming out of the back of the speaker is reflected around the listening room. This is why electrostatic loudspeakers must bepositioned well away from any walls behind them (see listening room design).
The best-known company is probably Stax from Japan. They developed the concept of headphones using electrostatic drivers, and call their headphones "earspeakers", although that might just be a consequence of translation from japanese! Another company with electrostatic models is Koss.
If you are interested in making your own electrostatic headphones at home, here is a guide to making your own: electrostatic headphones.
You might also be interested in other audiophile headphones.
Like the principles behind electrostatic headphones, but looking for something bigger? Have no fear! Click to see my guide to electrostatic speakers.
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