A plasma arc loudspeaker or plasma-dynamic loudspeaker is a loudspeaker that creates sound by varying air pressure through a corona discharge or electric arc. It is an evolution of William Duddell's "singing arc" of 1900 and, in recent times, modern research into spacecraft propulsion in the form of the ion thruster. In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor, which occurs when the potential gradient exceeds a certain value, in situations where sparking (also known as arcing) is not favoured. ... Electricity arcs between the power rail and electrical pickup shoe on a London Underground train An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, similar to the instant spark, resulting from a current flowing through normally nonconductive media such as air. ... Bory in 1872 in Britain, William Duddell was an outstanding electro-physicist. ... This article or section does not cite its references or sources. ...

Plasma tweeters are claimed to be an improvement on traditional tweeter designs because the driver has very little mass, and so low inertia, reducing distortion and increasing transient response. Because of their inability to move large volumes of air, they are limited to reproducing only very high frequencies, and are therefore usable only as tweeters. Most of those who have heard them claim they are notably sharp and clear. The principle of inertia is one of the fundamental laws of classical physics which are used to describe the motion of matter and how it is affected by applied forces. ... A Sony tweeter. ...

The operation of the speaker requires a continuous supply of ionizable gas. One model used helium; with the attendant problems of handling and refilling the gas cylinders. The plasma by-product, ozone, can reach hazardous levels in closed rooms. Due to their high cost, limited range, frequent maintenance requirements, and limited utility, they are rarely used in modern loudspeaker equipment, and are instead considered a novelty, perhaps with desirable aesthetic characteristics. General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Standard atomic weight 4. ... For other uses, see Ozone (disambiguation). ...

External links

• "The Audio Circuit" A site tracking, among other things, past and present brands of ionic speakers.
• LANSCHE AUDIO
• A loudspeaker with a plasma ion tweeter
• William Du Bois Duddell and the "Singing Arc"
• The Plasma Speaker Homepage
• History