Here at Dvice we love people who are willing to push the envelope into the danger zone to perfect their creations. Plasma speakers that drive the surrounding air directly through the expansion and contraction of a plasma arc have long been a sort of holy grail for speaker designers, but they also come with a dark side. Legendary maverick audio designer Nelson Pass once created a prototype full range plasma speaker, and ended up in the emergency room suffering from ozone poisoning. Following the incident, he was quoted in the Wall Street Journal as saying, "It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic."
Here's a video from a guy called Richard in England who has also built his own plasma speaker, using tungsten tipped electrodes and a whopping 60,000 volts to develop a pretty big plasma arc. He says it develops no ozone at all, but somehow I still think it would be tough to get it UL certified. Unfortunately the audio limitations of both Richard's camcorder and YouTube mean that you really can't appreciate the true audio potential in the video, but you've got to admit that it looks awesome.