A friend mentioned reading about plasma speakers which used to be some kind of high end autio esoterica. He remembers that you needed a compressed gas supply to operate them but I’m dubious about the plasma part. Has there ever been an audio speaker that operated with superheated ionized gas?
Here’s a link to a homemade plasma tweeter:
http://members.aol.com/uhaumann2/plasma/
I doubt it.
However, plasma by no means has to be superheated. Ever see those lightning globes? You know…the one that have colorful arms of light wiggling inside a sphere and are attracted to your hand when you touch the globe? Those are filled with plasma. They work because plasma can conduct electricity and are affected by a magentic field (such as is generated by your hand).
It’s probably exactly those characteristics that make plasma useful as a speaker although I’m just guessing about that.
Interestingly plasma is very rare on earth yet it is probably the most abundant form of matter in the universe.
http://www.arduman.com/aa/Sayfalar/london00.htm
“The plasma tweeter (see the macro picture showing the flame of the plasma at the back of the horn) is the most original part of the Acapella speakers (at least to me). They are the most perfect and neutral tweeters with a frequency response extending up to 100kHz (thus they also cover the area of a supertweeter without a crossover point). The use of plasma tweeters was abandoned many years ago due to the fact that they produce Ozone (O3). Ozone is very useful at the stratosphere levels but not in lower levels due to its aggressiveness and corrosiveness. It attacks nearly everything including our lungs! So, the rooms with plasma tweeters had to be efficiently aerated. Accapella’s designer expained to us that he solved this problem by the use of a ceramic and bronze cathalist which converts O3 to O2. He claims that it is 100% solving the problem and that we can even sleep in the room with the music on.”
Quoth Whack-a-Mole:
The plasma there is, in fact, at very high temperatures: It’s hard to ionize things without heating them. There’s just not much heat there, because the gas is so dense. That’s all I’ll say on the subject… For now.