It's kinda cool to think about though. To change atmospheric pressure in an open space requires a constant flow of a large volume of air, which requires a different kind of system. The larger the space, the more volume required of the pump. This is the kind of thing important to engineers setting up cabin pressurization systems, 'cause their systems must modulate the amount of pressure to compensate for altitude. Neat stuff.

I agree that no perfect square wave is possible, and that is a mathematical curiosity since a perfect sine wave is realizable. The perfect square wave isn't possible because of the fact harmonics content would have to be infinite.

But if we set limits, say slew rate less than 10µS and overring less than 0.1%, then we can discuss a realizable square wave. And I think that is realistic. That at least puts us in the realm of possibility, and I would argue that a square wave having 10µS rise/fall time and less than 0.1% overrring would sound absolutely perfect. It's a great goal. That then leaves us with the other issues to discuss.

We won't have much trouble finding signal generators and amplifiers capable of square waves with 10µS rise/fall time and less than 0.1% overrring, but we'll have a hell of a time finding electro-mechanical devices that can do it and an almost certainty of inability to find electro-mechanico-acoustic devices that can generate this waveform between 20Hz and 20kHz.

Obviously, an acoustic square wave is a discontinuity in pressure, which no speaker (piston) can produce.

As I see it, you are saying that the trained eye can readily detect speaker anomolies by examing the smearing at the transition areas in the measured output of the speakers when fed the proper signal. (I am a little fuzzy on how a triangle was related to "reproducing a square wave," however.)

Interesting. I'll buy that, but leave the discussion of what that means acoustically to others. ;)

Thanks.

I assumed it must be somewhere between 1.5 and 2 atmospheres for a sinusoidal piston motion that creates alternating compression and rarefaction. I also would guess that plenums, vents and other resonant chambers would have certain frequencies where they were more sensitive due to resonant conditions. At frequencies where a vent or plenum is resonanting, we'll get a ram-charge effect where critical pressures are reached at lower piston excursions.

But putting resonance aside, I wonder where air rarefaction/compression starts becoming noticably asymmetrical, causing non-linear distortion. Kinda thought you might know a reference or two.