What is vibration isolation for?

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.

Vibrations come from the speakers and particularly the bass, as was already stated. That energy shakes the audio chassis, the floor, the equipment stand and everything in the room to one degree or another.

A reviewer friend at Absolute Sound is so picky about this that he refuses to have his turntable and phono stage in the room with the speakers. He begins the track and walks back into the listening room and settles down for that side of the LP.

This stuff is very difficult to explain and probably even more difficult to measure. The easy way to see if there is a gain to be had is put aftermarket feet under equipment X and listen. The stock feet need not be removed to make the test unless they are so big that the aftermarket feet fail to touch the resting surface.

This is really very simple to do, costs almost nothing and will allow you to hear what the effect is. As I said before, you may have performance gain or loss depending on the many variables involved.

If you have no feet to try, I could ship you my spare Mod Squad Soft Shoes. They are my all time favorite low bucks device. They are successful on more types of equipment than any other foot I have tested.

I use more Squad feet in my system than other device, but still employ six other brands in one spot or another to get the desired results.

for a cheap experiment put some bubble wrap uner your CD player. With my ACR CD-2 there was a significant change. the sound tightened up and became quite dry. I didn't like it as much as the feet on the stand but the point is the difference is very noticable. cost of tweak if you like it...not being able to bust the bubbles on the packing wrap.