Rotating Plasma Vortex Speaker

[Anthony Garofalo] has made a fancier plasma speaker. Not content with a simple spark, he uses a plasma vortex. To make the vortex, the spark gap is swapped out for an electrode placed in the centre of a ring magnet. The Lorentz force experienced by the arc causes it to rotate rapidly enough round the arc of the magnet’s centre to appear as a continuous sheet of plasma.

The speaker gets its power from an inverter using a flyback transformer driven through a MOSFET by a 555-based pulse width modulator. You can see the result in the video below the break, it’s very impressive to look at but probably not quite ready to sit in your hi-fi stack. The resulting sound isn’t quite as good as that from a stationary arc, but it looks a lot cooler.

This may be the most visually impressive plasma speaker we’ve featured here, but it is not the first. Recently we featured another 555-driven speaker in a wooden enclosure, and back in 2010 we featured a how-to guide with a video for plasma speaker constructors.

27 thoughts on “Rotating Plasma Vortex Speaker

    1. The rotation comes from V (X) B from the Lorentz force equation. The magnetic field is perpendicular to the magnet, in a direction towards (or away from) the viewer. Current between the inner electrode feels a force which is perpendicular to the voltage (inner disk to inner part of outer ring) and the magnetic field (into and out of the plane of the viewer).

      Hence, electrons going from the inner disc to the inner portion of the magnet tend to curl around the inner disc.

      You might try using copper tape on the inside of the magnet hole as one electrode. This would be much higher conductivity, and shouldn’t affect the magnetic field.

      By not going through the resistance of ceramic magnet, you won’t dissipate as much heat. The magnet won’t heat up as much, and the speaker should be much more efficient.

      Also, 2 rings sandwiched together should give twice the B field, resulting in twice the curl.

      And, as someone mentioned below, this actually *is* a force field. Google “plasma window” for more info.

      People use plasma windows as a barrier between vacuum and normal air pressure. You can generate something in vacuum (X-rays, or a laser pulse) and then quickly turn the plasma window off to let the effect out into the atmosphere, then turn it on again.

      You can do this quickly enough that no air molecules get into your vacuum chamber.

      (Cool demo, BTW.)

      1. Also, you would probably get a better sound by using a sin wave to run the flyback instead of a square wave.

        You can get an AD9833 breakout board for almost nothing on eBay. This allows you to set the output frequency up to 2 MHz using any SPI device, such as an Arduino.

        This should filter out some of the high frequency audible sounds, giving you a less “buzzy” output.

        1. The “buzzy” output is because I’m playing a “buzzy” song on the vortex speaker from the article. The inherent fluttering sound associated with the plasma rotating can’t be silenced. Did you watch my regular setup with the two electrodes? The sound is very clear and can be heard from across the room. Also, I made a video explaining the Lorentz force and how to predict which way the arc will rotate. I also demonstrated that a larger magnetic field would result in a more sporadic vortex by using a much more powerful neodymium ring magnet.

  1. Always impressed with these (flame speakers too), some day I really ought to build one (Bluetooth shop speakers may be a good use…)
    But this makes me wonder, and maybe someone who knows more about the workings than I currently do… Could one be build as a Jacob’s ladder and still work?
    PWalsh mentioned that increasing the magnetic field would increase the curl, would this increase the field strength then too? Also mentioned that they can be strong enough to act as vacuum shutters, so, could there be a way to make the force field almost act as a “conventional” speaker cone?

    Just some food for thought that came up while I watched.
    Very cool

  2. Back in the 70s I heard a home-build HiFi setup which had a pair of Ionofane 601 plasma tweeters and Warfedale conventional mid- & low-range units built into large corner cabinets. Driven by active filters through 3 sets of power amps (Quad 303s?) my memory is of a very clean sound with transparent top end. We listened to some Pink Floyd and it was quite amazing. The demo with the the two electrode set-up sounds really good.

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