Plasma Tweeter Loudspeaker - A Singing ARC

Abstract

Plasma arc speaker is a loudspeaker that generates sound without a solid diaphragm by varying the air pressure and utilizing a high voltage arc. It makes sound by heating air that causes air to expand in the same way as in thunderstorm. The grumbles and growls we hear in thunderstorm come from the quick expansion of the air surrounding the lightning bolt due to sudden increase in temperature. This produces rapid expansion of the air impacting the surrounding cooler air at a speed faster than speed of sound creating a sonic shock wave, with a loud burst of sound. The 555 timer is used in the electronic circuit that acts like an oscillator and a modulator with a base frequency of about 23 kHz to drive a flyback transformer to generate high voltage plasma. It is modulated as per the audio signal when connected to the output of an audio amplifier and the size of the plasma varies in line with the audio frequency. The electric arc has a negligible mass. When current and frequency in the flyback transformer vary, massless plasma being ideal conductor also oscillates exactly in the same pattern of the audio input. As adjoining air is mechanically coupled to the vibraing plasma, it also vibrates and reproduces the sound source without any distortion. Using input audio electrical frequency, conventional loudspeaker viabrates a diaphragm to produce sound. But the inertia associated with mass of the speaker cone resists acceleration and other changes in cone position. Besides due to repeated sonic vibration the diaphragm suffers tensile fatigue. As a result of these physical limitations the fidelity of conventional tweeters at high audio frequencies are often imperfect. Being massless, plasma reproduces the sound source ideally without any distortion.