Plasma Tweeters

The most bizzare type of speakers with phenominal sound quality. Extremely clear and open sound; Perfect transient response; no Doppler distorion; extension to 60khz!....

The things that cause it to be inefficient are Rdc and the parallel resistance, Rac. Ideally, Rdc would be 0 ohms, and Rac would be infinite. What's left over is the Reactive components, Xac. The coil operates in self-resonance, where |Xac| is maximized. I use the absolute value "| |" because in self resonance, it is just at the point where the maximum inducance is being cancelled by the maximum capacitance of the windings. It is at this resonant frequency where the Rac goes way up (370kohms in my one coil). In effect, the optimum coil is the one that has the highest Q-factor. The Q-factor relates the voltage produced as a result of the oscillation to the bandwidth of frequencies over which the oscillation occurs, so a high Q coil has a very narrow bandwidth, which requires the feedback-driven oscillator circuit to keep it in optimum oscillation. It is important to wind the coil on a non-conductive core with about 2 thread's lengths of spead between the windings. I will be experimenting further with how to optimize these characteristics.

Article by Colin D. Joye at http://www.ee.vill.edu/~cdanjo/plasma.html