A tube is fabricated using piezoelectric material, and driven using encircling electrodes. The driving voltage is applied, delayed at the speed of sound, along the length of the tube. Thus a click would cause a pulse of contraction (or expansion) to travel along the tube, from the closed end towards the open end where it discharges the sound into the open.

The tube can be folded or coiled into a small volume, and allows a large area of actuator to air contact, without the cancellation effects due to a large driver area at high frequencies, yet move a large volume of air to reproduce low frequencies efficiently.
-- neelandan, Sep 26 2008

Bose Acoustic Wave http://www.bose.com...eguide_solution.jsp
Some info about how to put bass in tubes. [Amos Kito, Sep 26 2008]

Vey cool. (+)
-- MisterQED, Sep 26 2008


Interesting, but susceptible to a couple of problems: 1) The closed-end tube described will have a 1/4-wavelength resonance peak that may be hard to smooth out.

2) While the "phased line array" technique could work well over a limited frequency range, I have doubts about full-range capability.

+ for half-bakedness, but I'd like to see a better description of the signal processing required.
-- csea, Sep 26 2008


Would woofer and tweeter tubes solve the resonance problem? I mean with filters for frequency as well (do they do that anyway?).
-- nineteenthly, Sep 26 2008


Any tube has a resonant frequency, and stiffer materials create sharper peaks, floppier materials create flatter, wider peaks. Appropriate choices of tube sizes and stiffness can be overlapped in frequency to give a smooth wideband response. E.g. "Shotgun" style highly directional microphones use this technique in reverse.

Ported loudspeakers use the port to extend bass response lower that could be accomplished with the same driver in a closed box.

I imagine the peristaltic tube speaker could be like a set of pan pipes.
-- csea, Sep 26 2008


Could you get similar results by coiling the tube, then drive the side of the coil, so the tube's whole length is compressed all at once? Bigger amplitude, smaller driver volume.
-- elhigh, Sep 29 2008


No, the finite speed of travel of sound through the tube will tend to cancel out the high frequency components.
-- neelandan, Sep 29 2008


"Bass in a small volume" = small fish, or quiet fish?
-- elhigh, Sep 29 2008


If you coil it in a spiral, you'll get something approximately disc-shaped. A regular speaker is also approximately disc-shaped. I think that a speaker of this type will never be louder, and will probably be quieter, than a regular speaker of approximately the same size, used in open air.

This phased-array tube speaker produces a higher pressure, but with a smaller cross-sectional area. This results in a poor impedance match to the surrounding air, unless it's driving a small volume. So it could be good for earbuds, but for an open-air application, it would need a big horn to work well, and then you might as well just use a regular speaker.
-- notexactly, Jan 22 2019


Peristaltic tube speaker, my arse.
-- MaxwellBuchanan, Jan 22 2019



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