The recording I'm referring to is Pink Floyd's Pulse concert. It is only available in region 2, or an OOP ntsc disc, or LD bootlegs. I first heard this at my friend's place on his awesome Accustat+dual servodrive contrabass setup. Track 6 starts off with sustained guitar and synth notes and there is a very loud flapping sound. It's the sound of woofers pushed past their limits and hitting the basket(?). I thought he had some bass leaking into the planars but they were obviously fine. The weird thing is it's all just the recording. I closely monitored my own woofers and they are well within reasonable cone movement but it sounds like they are being torn off the surrounds. Is this bad for speakers? It's just another kind of sound, it just happens to sound like something bad is happening. The sound is just so seductive. Although it sounds like you're wrecking your mains, the sub vibrates your chair like one of those massage recliners. I'll run it through spectralab and post a screenshot. Perhaps even rip a sample (downmixed, the source is 5.1).