The history of ionic devices that create sound can be traced all the way back to 1899 with the "Singing Arc," a musical instrument based on the antique carbon-arc lamps that were used to light the streets of London. Physicist William Duddell was put to the task of figuring out how to quite the noisy lamps and ended up creating an instrument out of them when he found that varying the voltage to a lamp caused the singing frequency to change.^[1]

    Then, in 1946, Dr. Siegfried Klein tried using the corona discharge to create sound. The invention worked. Dr. Klein patented the invention under French patent number 1,041,790, and US patent number 2,768,246. He experimented with different emitter materials to find which would last the longest and sustain the flame the best. In 1954, work started on producing the ion tweeter with DuKane in the USA as a commercial product, which first came out in 1956. The ion tweeters were also sold in England, Germany, and France under names such as IonoPhone, Ionovac, and IonoFane.^[2]

    Much later, Dr. Klein came out with several patents on other ion tweeter designs under patent numbers 4,306,120, 4,464,544, and 4,482,788. These patents were filed between March 1980 and July 1982 (granted as late as November 1984). Two of these patents did away with the horn-loading that was used on the early tweeters and concentrated on 360-degree sound dispersion. Even these new designs, however, used vacuum tubes extensively.

    Finally, in 1993, Dr. Klein was able to do away with the vacuum tube technology and create a working prototype ion tweeter using only solid-state devices, which was put into production by the German company MAGNAT under the model number MP-02. The design used only Bipolar-Junction-Transistors (BJT's), and a multitude of special size inductors and several variable capacitors. While this design probably showed an improvement in wasted heat over the vacuum tube design, it could have probably been improved further be using high-current high-voltage Field-Effect-Transistors (FET's). Quite possibly, Dr. Klein could not find suitable FET's at that time to work at the high voltages present in such a system. MAGNAT MP-02 Schematic ^[3]

    Today, many high-voltage and high-current FET's are widely available. Such FET's even beat vacuum tubes in terms of cost and availability. In terms of efficiency, there is no contest between FET's and vacuum tubes. Some FET's have turn-on resistances of well under 1 ohm, while a vacuum tube can typically drop 100 volts or more when "on". In order to maximize the efficiency, we will explore Pulse Width Modulation (PWM) as a way of combining audio frequencies to the high-voltage oscillator in our design.