Helium Plasma Speakers (Jun, 1979)
Coneless speaker uses plasma driver
“Jack’s Welding? My loudspeakers are low. Fill ‘em up with helium, please.”
Strange phone call? It’ll be routine for affluent audiophiles using a new speaker system, the Hill Type 1. Type 1 cabinets contain a helium bottle good for about 300 hours of playing time. Minute amounts of helium bleed into a glowing plasma, or highly ionized gasâ€”heart of the speaker from Plasmatronics Inc. (2460 Alamo, S.E., Albuquerque, N.M. 87106).
Laser physicist Alan Hill, who developed the system, won’t detail his patent-pending plasma drive. But the big advantage of a plasma is that it’s virtually massless. Conventional speaker cones or membranes can “color” and distort sound because their mass takes time to move and stop. The lavender-colored, incandescent plasma in the Type 1 excites air molecules directly with electric forces. Result? Listeners say subtle musical nuances are reproduced with startling realism.
The plasma section of the Type 1 is not set in a conventional acoustical enclosure that can color sound. The reason, says Plasmatronics: Sound radiates outward from the plasma in a sphere of waves that are in phase. Out-of-phase air waves from ordinary speakers require enclosures.
Type l’s actually have three speaker elements: a heavy-duty, 14-inch subwoofer, a 6.5-inch midrange driver, and the plasma transducer. The two conventional speakers handle frequencies from about 10 Hz up to 700 Hz. Owners must supply a stereo power amplifier to drive these speakers. The plasma section has its own amplifier, and reproduces frequencies from 700 Hz into the ultrasonic range.â€”John Free