The Pyro Board: A Two Dimensional Ruben’s Tube



Like visualizing music? Love fire? If so, you’re going to want to take a look at this Pyro Board.

What happens when you take a tube, put some holes along it, add a speaker on one end, pump some propane in, and then light it on fire? You get an awesome fire visual — also known as a Ruben’s Tube. It works because the sound pressure from the speakers causes the flow rate of gas leaving the holes to vary, which results in a visible “standing frequency” of flames, i.e. a flaming VU meter.

The folks over at [Fysikshow] decided to step it up a notch by building a 2-dimensional Ruben’s tube with 2500 holes. They have a steel box with the evenly spaced holes on the top, and two speakers attached to the sides. And it works amazingly well — see for yourself after the break.

Based in Denmark, [Fysikshow] travels to schools teaching kids about physics using the Pyro Board and many other fun experiments.

[Thanks Eren via This Is Colossal]


  1. zibri says:

    very nice idea, but too much interference.

    • tim says:

      this whole thing is about interference.. standing waves are interferance of waves of constanty equal frequencies..

      • John Smith says:

        Technically yes, but you know exactly what he meant. The is too much spurious ‘signal’ (flames) and the board fails to show a good representation of standing waves. This could be to bad gas flow, or maybe even weird reflections in the square corners of the box.

  2. AussieTech says:

    Interesting display, but this is NOT an “equalizer” FFS.

  3. AlanH says:

    It’s pretty insane now. However if you fine tuned a series of band pass filters going into the box to get rid of most of the noisy intermediate node frequencies, it could be more spectacular. One could make a nice living building, tuning and selling these to clubs, ski resorts, and other social businesses all over the world (as long as you were insured and bonded!)

    • AlanH says:

      My guess is it might be more successful with a round base so you never get an orthogonal reflection. To me it seems waves would better propagate and constructively amplify at the right note if you interjected them at an angle and they bounced around a circular perimeter. However I assume the guy likely tried it already and this is the shape that works best.

  4. JustSo says:

    They set up a big, experimental flame machine in a bedroom! Awesome, and none of the schoolkids will ever forget the standing waves.

  5. freelancer says:

    Absolutely love it!

  6. Greenaum says:

    I think the 2D-ness robs it of the impressiveness a Ruben’s tube has. Watching waveforms pump out along a Ruben’s tube, standing wave or not (in fact, “not” looks better) is immediately impressive. Particularly with bassier sounds where you can literally see sine waves made of flame.

    A Ruben’s tube is pretty much 1-dimensional, so the waves look like they do in textbooks, really wave-like. I think the nature of the 2D thing, letting them spread out, and the interference, spoils the effect quite a bit.

    OTOH might be a nice effect in a nightclub, or at Burning Man or something. Presumably kept in a strong glass case, for safety.

  7. Greenaum says:

    The grid gives me another idea though. Do you think, maybe with thermostats or valves of some kind, you could do something like Conway’s Game Of Life on one of these? With lit cells being “alive”. Conway’s rule just needs to sum up the living cells to decide the next generation, shouldn’t be too hard to match that to a certain amount of heat input.

    Maybe it’s harder than I think, maybe it’ll get too warm eventually and stop working. Just something that struck me watching the tiny flames moving round a grid.

    • macegr says:

      It looked like it actually was already playing Conway’s Game of Life. There are finite resources of air and fuel, and if too many flames were in one location, some would go out. Other flames that happened to be near a resource-rich area would start new flames there.

  8. David says:

    The tube is named after Rubens. Why is there an apostrophe in there? Oh yes, the story was by Jame’s Hob’son.

    • rj says:

      It’s like the advice the tour at Johns Hopkins gave me when I was looking at colleges: placing any apostrophes in their name was a sure-fire way to guarantee you would not get admitted.

  9. rmd6502 says:

    A triangular or trapezoidal Rubens plate would have different resonances along its length – a DFT with fire!

  10. supershwa says:

    …you had me at “pyro”!

  11. tom says:

    Plus it heats the apartment!

  12. Ty Tower says:

    Thats a brilliant way of teaching young ham radio operators what Standing Waves are!

  13. Hirudinea says:

    Ok, call me weird but with tighter control this would make the most badass cook top ever!

  14. steve says:

    Love this

  15. That one guy says:

    A flaming VU meter? FAAABULOUS!

  16. deadlydad says:

    I may have missed something, but I’m thinking that oxygen starvation would be an issue in a 2D array. If the flammable gas was premixed with oxygen, it should work better.

  17. Galane says:

    What would be really impressive is a round one that could do circular standing waves.

  18. Jerzee says:

    I wonder how a cube would work to include surround sound input.

  19. Sean says:

    Hey how much will you charge to make one???? That shit is tight I have a pyro Board but your is beast

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