stringreen,
Herbie's gizmos "absolutely ruined the sound"
I've no doubt that's what you experienced, but I have to say in my experience I have yet to encounter any loudspeaker that didn't sound better with some form of isolation underneath. Even my portable Sony radio sounds a tad better when placed upon a compliant surface.
It's certainly possible that many loudspeakers were designed to be placed on spikes, and that's where they will measure and sound best. I just haven't encountered one like that yet, but that is far from conclusive.
It would be good to have designer feedback here, as the only thing I've read was by Alan Shaw from Harbeth who once said he was happy to test his top of the range M40s placed on top of some telephone directories.
However these are only just my impressions, and I prefer an organic midrange sound to one that might be deemed to have a tight precise bass output. This should be easy enough to test, at least with my radio, once I can get someone willing to assist me in a blindfold experiment without too much derision.
Anyway the evidence, what there is, seems to come in the form of baffle accelerometer readings which heavily favour any compliant feet over any spikes.
However panel resonance is a tricky business as this article tries to demonstrate.
http://www.tonestack.net/articles/speaker-building/cabinet-sound-insulation-measurement.htmlIn any case the old argument about Newton's first law of motion is not very helpful here. The forces generated by the movement of the low mass cone in comparison to the large mass of the cabinet are virtually insignificant.
For the driver motion to actually move the speaker, the cabinet would need to be placed on a very low friction surface and the volume output would have to be comparitvely huge, with huge panel resonances to match.