It was Heil Plasmatronics. They burned a helium. $7k a pair in 1976. I actually heard them at a store called Absolute Audio in Santa Ana. Fabulous sound. The best speakersvI have ever heard. No cones to produce sound above 600 hz. Hence no distortion from lag time of paper cones . It was strange watching a flickering purple gas emit music. Impressive. The inventor is a laser physicist. They took them off the market as they posed a slight health risk.
Plasma speakers anyone with info?
I can find many sites for diy but cannot find any for sale . Help! Nick