Plasma arc speakers, also known as ionophores, are a type of loudspeaker that modifies air pressure with a high-energy electrical plasma. When connected to the output of an audio amp, the plasma speakers change the size of the electric arc, the plasma glow discharge, or the corona discharge. Eventually, they operate as a massless radiating element. This process creates the compression waves that the human ear perceives as a sound. Tweeters made of plasma arcs have no resonance or transient conflicts.
Plasma Arc Speakers: Their Construction
Speakers use a variety of materials within their construction. The lighter the material, the faster the response. Lighter materials tend to produce better transients, and plasma arcs have no weight at all. In this context, the speaker operates by modifying the temperature and moving the airflow.
Plasma arc speakers were invented by William Duddeles at the beginning of the 1900s as an evolution of Singing Arc and an innovation related to ion thruster spacecraft propulsion. The invention of the ionophore emerged when its creator discovered that by varying the voltage of the arc, the sound generated also changed. Decades later, Siegfried Klein tuned the arc speaker by inserting the arc in a quartz tube. He then got the idea of connecting this device to a horn, therefore creating both a speaker and a microphone. Years later, DuKane Corporation manufactured the air-ionizing Ionovac. Nowadays, this design is still in use and easily available to the public.
The first designs of the plasma speaker ionized the surrounding air through both nitrogen and oxygen. In an intense electrical field, both oxygen and nitrogen generate a reaction. In closed spaces, they can be quite dangerous.
Types of Plasma Arc Speakers
There have been several varieties of plasma arc speakers. Plasmatronics manufactured a commercial version that involved a helium tank to ionize the gas. Years later, the Air Force Weapons Laboratory designed a commercial helium-plasma tweeter known as the Plasmatronics Hill Type I. This device avoided the nitrogen and ozone oxides produced by the radiofrequency decomposition of the air. The design of the Plasmatronics Hill Type I depended on a quieter glow discharge mode. It’s worth noting, though, that these speakers need a constant supply of helium.
ExcelPhysics and Image Scientific Instruments provide their own version of plasma speakers, making them more affordable and available to the public. The design by ExcelPhysics uses a flyback transformer that helps elevate the voltage. It also includes an audio amp, a 555 timing chip to achieve the accurate modulation, and a 4Hz carrier signal.
If you need other options…
Similar to transparent ionic conduction speakers, these are quite innovative. If this technology isn’t for you, try learning from digital, electrodynamic, full-range, mid-range, woofer, subwoofer, and coaxial speakers. You can also consult piezoelectric, magnetostatic, and magnetostrictive, and planar magnetic ones. You can, too, delve into flat-panel loudspeakers, such as ribbon and electrostatic. The world is your oyster!