883dave, I am going to try and explain what an isolator really is and what it does refering to my textbook and some catalogs I use at work. Firstly, I did skim through the stereophile article mentioned above and it is somewhat confusing since it mentions the best you can do is 100% transmission and then the last few pages are about proper isolation/damping. Their conclusion then was getting a rigid, sturdy rack and then isolating the source components individually so even if I didn't know better, I wouldn't just put cones under everything. Can you imagine being rigidly coupled to the wheels of your car without springs and shocks? I cannot comment on the stuff about effect of vibration on passive components and phase shifts and such.
To put it simply, every material has a natural frequency at which it will vibrate when subjected to a disturbing force. Natural frequency of a system depends on several variables including stiffness of the material used, mass, shape etc. In general, lesser the stiffness, lower is the natural frequency.
Vibration is a force and establishing an opposing force can effectively reduce it's transmission. This is the function of an isolator. Simply put it is a spring. It can be a steel spring, air spring or an elastomeric spring. A damper is a device by which vibrational energy can be dissipated, typically by converting it to heat. A steel spring is only an isolator whereas an elastomer can be an isolator and a damper. An isolator must deflect under load to oppose vibration. NO PROTECTION WITHOUT DEFLECTION! The fundamental property of an isolator is it must be resilient, ie, it should be able to return t it's original state without load.
An isolator is defined by 2 properties, it's own natural frequency and how much it can deflect (in our case compress) under the maximum allowable load which is dictated by the material and structure and is called static deflection. In general, the greater the difference between it's natural frequency and the disturbing frequency, the better the efficiency of isolation. The greater the static deflection, the more effective the isolation. Deflection however should be limited to the direction of travel of the force, usually vertical thru the isolator. An isolator must be constrained to limit horizontal movement although there are devices that isolate in shear also.
Pneumatic springs have the lowest natural frequency, can be as low as 2Hz and are excellent for audio purposes. However by using only an inner tube or soft feet you get plenty of sway. If you look at typical isolators in Lord, Mcmaster etc, the elstomers are bonded to some steel to add rigidity to prevent this. They are inexpensive and can be mounted between a shelf and a platform for the source. I don't know what a vibraplane mentioned in the review is but I am sure it is a platform with constrained air springs. Bright star may has one also I think. Usually precision lab equipment is isolated using some type of spring. As the article says, "draining vibration" with fancy hard substances underneath your component is all bunk, sorry.
