Plasmatronics

Plasmatronics was a company, founded by former Air Force Weapons Laboratory (now Phillips Laboratory) scientist Dr. Alan E. Hill, which produced a plasma speaker design. This was first demonstrated at the 1978 Winter CES show [1] .

The product was effectively a loudspeaker with an integrated amplifier; however, it used a gas plasma, sourced from a helium tank in the back of the unit, as a near-massless driver. The plasma driver only reproduced the higher frequencies as a tweeter; the lower frequencies used a conventional woofer driver.

While praised for accurate sound reproduction at demonstrations, the system had a number of disadvantages, including high cost, and the periodic handling of heavy compressed helium cylinders. Although widely rumored to have produced corrosive ozone, the high temperature discharge actually destroys the gas. There were, however, other unidentified by-products of the discharge with a distinctive odor.

[http://www.nutshellhifi.com/library/speaker-design1.html The Art of Speaker Design]