# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DdMimkKhOyQ
- **Gondola URL:** https://gondola.cc/posts/70280829-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/63527ea13c.jpg
- **Posted:** 2026-09-12T17:39:27.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

A plasma speaker has no cone, no voice coil and no suspension. The diaphragm is the arc itself.

Every conventional driver moves air with mass. A cone bonded to a coil accelerates inside a magnetic gap and drags the surrounding air with it. That assembly has inertia, and inertia smears transients and caps high-frequency response. A plasma speaker deletes the moving mass entirely.

The mechanism is thermoacoustic rather than mechanical:

- A high-voltage supply, typically a flyback transformer switched by an IGBT under a 555 astable or TL494 PWM stage, sustains an arc across a small electrode gap. Dry air breaks down near 3 kV per millimetre, after which the ionised channel turns conductive and the voltage across it collapses.
- The channel runs at several thousand kelvin. Audio is impressed on the carrier by modulating pulse width or switching frequency, which modulates the power dumped into that channel.
- Rapid heating and cooling expands and contracts the air around the arc, radiating pressure waves directly. Sound pressure follows the rate of change of heat input rather than physical displacement, so nothing ever has to be accelerated.
- The carrier is parked above 20 kHz deliberately, leaving the arc silent until audio modulates it.

The trade-offs are severe. Transient response and treble extension are exceptional, with no cone breakup modes to control. Bass is effectively impossible, since low frequencies demand volume velocity and a millimetre-scale arc cannot displace enough air. Electrical efficiency is dismal, and an arc burning in atmosphere manufactures ozone and nitrogen oxides as a byproduct.

Hermann Theodor Simon published the effect in 1898 and William Duddell made his singing arc play melodies in 1900. Siegfried Klein named the ionophone, licensed to DuKane as the Ionovac and to Fane as the Ionofane.

The finest diaphragm ever engineered is the one nobody had to build.

#stemantics #plasmaspeaker #highvoltage #audioengineering #physics

## Stats

- **Views:** 5,628
- **Likes:** 171
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## Tags

audioengineering, plasmaspeaker, physics, highvoltage, stemantics

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