Plasma speaker

Plasma speakers (sometimes called flame speakers if the source of the plasma is combustion rather than gas ionization) are a form of loudspeaker which vary the intensity of a plasma, rather than using a magnetic field to push or pull a conventional driver, to create compression waves in air (which a listener perceives as sound).

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In a normal loudspeaker design, the inertia of the driver will resist an instantaneous change in its position as the magnetic field varies with the input. This decreases the fidelity of the speaker, as the input is distorted due to the physical limitations of the device, particularly for strong high frequencies. (This limitation is one of the reasons why tweeters are so much smaller than woofers.) In a plasma speaker, this limitation effectively does not exist, as the air itself is driven directly by expansion of the plasma as the current passing through it varies. (Ionization of a gas causes its electrical resistance to drop significantly; see for example the "Jacob's ladder" for an explanation.)

Plasmatronics produced a commercial plasma speaker that used a helium tank to provide the ionization gas; other designs (some of which date to the 1950s) use combustion of natural gas or even candles^{[citation needed]} to produce a plasma, through which current is then passed as in the gas plasma designs (though combustion designs do not require the initial high-voltage to create the plasma).

The plasma speaker design is a member of the family of so-called massless speakers.

References

• The Audio Circuit A site tracking, among other things, past and present brands of ionic speakers.
• The Art of Speaker Design