Is It A Plasma Tweeter Or A Singing Tesla Coil?
When our ears resolve spatial information, we do so at the higher treble frequencies rather than the bass. Thus when setting up your home cinema you can put the subwoofer almost anywhere, but the main speakers have to project a good image. The theoretical perfect tweeter for spatial audio is a zero mass point source, something that a traditional speaker doesnt quite achieve, but to which audio engineers have come much closer with the plasma tweeter. This produces sound by modulating a small ball of plasma produced through high-voltage discharge, and its this effect that [mircemk] has recreated with his HF plasma tweeter. A look at the circuit diagram and construction will probably elicit the response from most of you that it looks a lot like a Tesla coil, and in fact thats exactly what it is without the usual large capacitor hat on top. This arrangement has been used for commercial plasma tweeters using both tubes and semiconductors, and differs somewhat from the singing Tesla coils you may have seen giving live performances in that its designed to maintain a consistent small volume of discharge rather than a spectacular lightning show to thrill an audience. You can see it in operation in the video below the break, and its obvious that this is more of a benchtop demonstration than a final product with RF shielding, Its not the most efficient of devices either, but given that audiophiles will stop at nothing in their pursuit of listening quality, wed guess thats a small price to pay.