Plasma speaker builds usually stay in novelty territory, but this one treats the idea as a genuine tweeter. Magneticitist housed the working unit inside a black plastic toolbox, and the maker describes the result as a great tweeter with unusual clarity, though not super loud.
The circuit sits on a flat metal plate that doubles as a heatsink strip, with a red PCB carrying electrolytic capacitors, screw terminals, an IC and a rotary pot. An LM386 amplifier board takes a 3.5 mm input, an XY-PWM board generates the drive signal, and an IRFP4232 MOSFET switches the primary of a TV flyback transformer. A 120 watt Mean Well supply feeds the unit at around 20V and 5A, while clean 20-25V DC runs two buck converters. Inside the box there is an aluminum heatsink with a cooling fan, and the side panel carries a toggle switch, potentiometers and a red voltage readout. A digital panel meter tracks frequency and duty cycle, and the maker also drew a hand-drawn circuit diagram.
Tuning comes down to adjusting gate drive voltage, PWM frequency and the trim pot, and the setup lets the maker change volume and quality on the fly. It runs near 25 kHz at 60% duty cycle, and the maker hears it clearly above about 150 Hz. As a bonus, a radio next to the arc keeps its tuning untouched, and there is no ozone smell at all from the hot whitish arc.
There are trade-offs, of course. Audio pops at times, and dropping the volume stops it but costs loudness; driving closer to 20V or more brings clear volume back without popping or distortion. The electrodes are still being perfected for a longer solid arc that holds steady, and the maker admits not knowing the real consensus on ozone safety when a fairly big arc is needed for good volume. A clear plastic container over the electrode shields the arc from air currents, a practical touch in my opinion.
Project by Magneticitist. Watch it on their YouTube channel: