The physics of roller bearings, pt. 1
The reason vibration isolation is important is that low frequency vibration and forces related to that vibration affects the audio signal, including but not limited to the wiring in the wall, the wall outlets, the wall plates and the wall itself, wire in cables and power cords, internal wiring and electronic elements in the components and speakers. The audio signal itself is not (rpt not) a vibration per se or at least it SHOULD NOT BE but is affected by forces F of external vibration. Like magnetic field lines on a magnet are affected by rapidly moving the magnet manually.
The entire building is subjected to continuous seismic waves that are produced by many things including Earth crust motion, wave action on shore lines, trucks, buses, subways, cars, construction, footfall, wind. The entire building is forced to move in many directions. Seismic waves have six directions of motion, including three rotational directions. The horizontal plane x-z represents the other two directions 🔛, vertical y is the sixth direction 🔝. The three rotational directions are around the x, y and z axes.
The analogy to seismic waves and its influence on a building and everything inside the building is a boat ⛵️on the ocean when a waves in one direction passes under it. The boat moves vertically, sideways and also rotates back and forth as the wave passes under it. Waves in other directions affect the boat similarly but the boat moves in different directions according to the direction of the other waves. In order to reduce or eliminate forces F that seismic waves produce on the audio signal the entire audio system should be isolated, decoupled from the building. An object will remain at rest unless acted on by an external force. I’m disregarding acoustic waves in the room for this part of the explanation.
Roller bearings are interesting because they are capable of isolating the component in several directions of motion, low in cost, depending on how the roller bearings are designed. The most simple design is a cup with a flat bottom that has small diameter base so the ball can not move very far. Three of these roller bearing assemblies will provide good isolation in the horizontal plane and in the twist rotational direction around the vertical y axis. If the cup is concave the component can be isolated against forces in the other two rotational directions. The roller bearings are not effective in the vertical direction, well, perhaps a bit, never say never. The vertical direction can be easily handled by springs, very effective in the vertical.
Materials for the cup and bearing should be chosen with the goal of keeping friction very low, I.e., smooth very hard surfaces.
