What is vibration isolation for?

After reading Pbb's thread I couldn't help but think of the old tale 'The Emperor's New Clothes'. I think that pretty much sums it up.

Albertporter, back to my original point. Anything UNDER the component is not isolation. Isolation would mean putting the components in another room - away from the air movement caused by the speakers. I don't care what you put under your electronics - as long as the bass is pounding on the chassis like a tin drum, aint no rack gonna fix that problem.

Neubilder, things under the chassis are isolation if they help reduce the effect of outside forces effecting performance.

A rubber foot under a preamp can alter the resonant frequency of both the preamp and the shelf it is resting on. The shelf and preamp may both be vibrated by the same bass pounding (your description), but as long as the foot reduces or alters the frequency of the vibration, there will (likely) be a change in sound.

I will not argue that all changes are good. Some rooms, shelves, equipment chassis (etc.) benefit from a certain isolation device or foot, and not another.

There are other ways to effect or isolate the equipment, such as shelf materials that block magnetic energy or RF. There are damping sheets that may be applied directly to the chassis, inside or out that reduce the ring of the materials it is attached to.

Some prefer the sound of equipment with a weight applied to the chassis. There are many ways to pull that off, some expensive and some for free. Again, this changes the resonance of the chassis and or the material it is sitting on.

My point is that there is a change, and all of the ways I have listed may make a sonic difference. Some will be perceived as good, some trade off and some as bad. The whole point of discussing tweaks like these are so others may experiment and find what works for them. I never dismiss any idea until I have put it to the test.

Albertporter, where are the vibrations coming from that audiophiles are trying to cancel/alter. The music within the room? Or is it something else?

Unless we're talking about turntable playback, the sound output from your speakers are not a likely source of vibration induced distortion in a hifi system. (I'm assuming reasonable sound levels and the avoidance of narrow band resonance excitations.) There simply isn't that much energy in the sound waves. A much more common problem is vibration transmitted from the speaker directly through the floor or walls. Rooms with wood floors in wood framed houses suffer this type of problem. I've placed my subwoofers on Vibrapods to isolate them from the floor. The total cost of this tweak was about $100 which is relatively cheap and a very small percentage of the value of my system.