J. Gordon Holt writes: Dr. Alan Hill, president of Plasmatronics Inc., was previously employed by the US Government in laser research. His assignment: To increase the efficiency of lasers so that they could do something more impressive than produce holograms, mend leaky retinal blood vessels, and punch pinholes in steel blocks. Dr. Hill earned his keep, thus advancing laser technology a giant step closer to Star Wars, and then retired from government service to design. . . a loudspeaker?!!!?
How could laser research qualify someone to design a loudspeaker? The connection is really much more direct than it seems. Twenty-odd years ago, Dr. Hill envisaged a loudspeaker that would use a field of ionized air as the transduction element, but didn't feel enough was known about plasmas (footnote 1) to perfect such a device. At about the same time, a firm called the Dukane Company started producing such a device anyway: The "Ionovac" tweeter. It was not a huge commercial success, partly because of its (for those days) outrageous price and partly because add-on tweeters have never been big sellers. (The Ionovac was subsequently made by ElectroVoice until phased out in 1963.) Nonetheless, the Ionovac is still considered by the knowing to be the best supertweeter ever made, and there are few audiophiles who would sniff at its 2–40kHz (±2dB) response.
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