Short of "Star Trek," I don't see how such a device could be made to work in practical terms. It would seem that the amount of material would be finite & quantifiable, but the cylinder would have to expand and contract. Since the mass would be the same, the material would have to stretch, meaning that with each "pulse" or cycle, the thickness of the diaphram would change, probably with amplitude or frequency. I can't imagine how the response would be linear.
Moreover, I'm not sure why you'd want an omnidirectiona tranducer. Theories vary, but it's certain that you'd get a lot of "room sound" for a very low practical signal to noise. The current trend seems to be greater directivity, not less, in order to mitigate the effect of the room on the sound. Companies like Legacy & VMPS has invested a lot of R&D into just such avenues, trying to remove the room from the equation as much as possible.
The Ohm speakers were pretty well reviewed, and the Mirage Omni's have their followers, but neither coud do exactly what you describe. And look at the famous B(l)ose 901's- they try to use the walls pool table style to add to the sound, and they're just friggin' dreadful!
