Plasmatronics is 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 Consumer Electronics Show.
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, periodic handling of heavy compressed helium cylinders, and ozone emissions that may become hazardous in an enclosed room.