Audio Technica manufactures or has manufactured the following equipment (click to expand models list):CD-Players
Imorama (February 2003): Audio-Technica also made OEM products. One of them is Signet. Signet is "Signet Division of A.T.U.S", exactly, and A.T. means Audio-Technica here.Signet TK33 and TK44 are probably OEM models of A.T.'s ATH-8 and ATH-10, respectively.
Joerg Baar (June 2001): The Audio-Technica headphones HTA-6 and 8 and 10 are no real electrostatics. I am informed about these types and definitely know that they are of electret-style.
The electret style phones use a special handled diaphragm in which the "high-voltage" is already built in. There is no need of a bias-source, only audio transformers are neccessary to feed the electrodes. Although the electric principle is the same as the one with real electrostatics,- the built-in loading of the diaphragm tends to flush out after years of use so that this kind of phones tend to decrease in loudness with time. I had phones that almost did produce no sound at all due to the lack of loading in the film. There are a lot of electret-style headphones around, many of them use the same system,- it is a system that is produced by STAX. The STAX SR-3 0& SR-40 are electrets, the Sennheiser UNIPOLAR 2000/2002 are also electrets, same is with the MicroSeiki MX5 and the described Audio-Technica models. As a rule you can say that the cheaper models of a brand are made as electrets.
I do not exactly know, what procedure is undertaken to the foil to get it loaded as an electret. As far as I know, it is Mylar again. Electrets of today use foil thicknesses of about 1um, therefore the sound reproduction is almost as good as with real electrostatics ( as long as the electret is new) . The principle was first used for microphones in the 60s. Same experiments where made to built electrostatic speakers using the electret-technique, but it did not come out ever.
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