vibration control

An electromagnetic field is subject to a number of things, including as you suspect, static electric fields. But we have learned that the electromagnetic field - the audio signal carried through wires and cables is also subject to magnetic interference as well as mechanical interference.

On need only look at vibration isolation of turntables, CD players, DACS, solid state and tube amps to conclude that the seismic type vibration - due to Earth crust motion, subways, trucks, etc. - that affects the entire house is making its way up into the component and degrading the sound (without vibration isolation). When the component is isolated from the structural vibration one can appreciate that the vibration must have been degrading the sound.

Perhaps you've seen the experiement when a magnet is shaken the magnetic field lines that normally appear stable and uniform around the magnet become disturbed and move around and can even become detached from the magnet.

In normal operation a capacitor vibrates, thus damping the capacitor reduces the vibration, resulting in better sound.

So, we have acoustic vibration from the speakers to worry about, also vibration generated by the component - motors, transformers, capacitors, etc. - and structureborne vibration that vibrates the walls and floor. The structureborne vibration is a form of mechanical feedback when it makes its way from the floor to the component. Footfalls on wood floors are a good example of this mechanical feedback, or a bus passing over a manhole just outside that causes the needle on the record to jump out of the groove. The vibration of the walls and windows is another problem, producing acoustic signals that interfere with the primary signal from the speakers.

I undestand the need to isolate a turntable, and to properly seat a speaker to a solid stand or the floor. But I do not understand how an amplifier will be affected when almost every speaker company uses a passive crossover in an environment with constant vibration, and exposure to the electromagnetic field of the drivers and the wire in the speaker.

09-06-11: Geoffkait
An electromagnetic field is subject to a number of things, including as you suspect, static electric fields. But we have learned that the electromagnetic field - the audio signal carried through wires and cables is also subject to magnetic interference as well as mechanical interference.

i have to admit that this is a *truly* creative explanation.

My experience with isolation and dampening of stereo components has yielded more focused images, more detail and tighter, more detailed bass response. First, a very obvious improvement is cones under the speakers. My Thiels come with cones, as do many speakers. When roughing in the position of the speakers on initial set-up, I left the cones off. Images became focused and crisp once I put the cones back on. Very obvious change. The other big change was when I remodeled the room by replacing the carpeting with a 7/8" Hickory wood floor. The bass response was the biggest improvement. I know the additional thickness of the wood made the floor much stiffer. Room response can be a key element in good sound. I have had my stereo on a concrete slab years previous in a different house. I think a concrete floor is too stiff and deadens the music. Of course, speaker type may play into it too. And a carpeted floor can be fine too, provided the sub-flooring is stiff enough. I had one buddy who added braces to his sub floor. He had an unfinished basement so he could do that. It made a difference.
I had my turntable, CD player and Amp sitting on Granite slabs for years. Of course, these components had additional rubber dampeners on top of the granite. One day, I stuck my wife's bamboo cutting board under the CD player. The change blew me away. So under the CDP is one cone about where the motor rests, and two Sorbathene feet. And then under the bamboo board are three closed cell foam pads. Then the granite then the cabinet shelf. The cabinet feet are on spikes on my precious wood floor.
So I tried the bamboo board under the turntable. It changed the sound too. I wasn't sure that I liked the change, but when I added three closed cell foam pads between the wood and granite, then I liked the sound.
So here is the kicker. I put a bamboo cutting board under my big brute of an Amp and the improvement in sound was again astounding. So the amp sits on the bamboo board which is on a granite slab, then four isolation disks and then the wood floor. I never expected a change just by putting a wood board under the amp. One conclusion I have is, granite slabs are good for adding stabilizing mass, but components do not react well when coupled to the granite, even with rubber isolators in between.
Another experiment that did not yield good results: I tried subsitituting 70 durometer rubber strips in place of the closed cell foam pads between the wooden boards and the granite. I did this under the CDP. The highs sounded awful and even had a shrill sybillance. I left them there for a couple of weeks. I almost forgot about them and actually was starting to wonder if my CDP was going bad. Then I remembered putting the rubber pads under the wood. I pulled them out and the highs returned to normal. A remarkable difference in sound and I have no clear idea why. I would have thought those rubber pads were too far removed from the CDP to matter much.
So, experimentation is required. One type of dampener might produce good results in one system but not so good in another. I recommend not investing too much money in these materials. The brass cones and Sorbathene feet are the most that I have ever spent. The bamboo cutting boards were not too expensive. They were certainly cheaper than some special audio boards or even carbon fiber boards. Not saying those wouldn't work even better. Just trying to keep costs down.

I used a couple of Townsend seismic sinks, BDR cones, Sympoisum roller blocks, butcher blocks,all of them are better than nothing.

But the biggest change was when I bought a Grand Prix Audio rack.

Pricey, but the best isolation device I've yet encountered.