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Zach,Called spikes or footers, they concentrate the weight, thereby increasing the bearing stress (pounds per square inch). This is only effective when the supporting material deforms, either elastically (meaning it will "rebound") or plastically (meaning you've made a permanent dent/puncture). Without deformation there is nothing added to reduce resistance to lateral (or upward) forces. Carpets/rugs are the best supporting materials to apply spikes as you normally penetrate the carpet/pad or rug and are bearing directly onto the hard floor below. In this way the mass (weight) of the speaker is coupled downward with the floor. Notice that I stated "coupled downward" as it is only by gravity that any coupling has occurred. Vibrations can be caused by mechanical transmission (through solid objects in contact), self vibration (yes even electronics and turntables/CD players vibrate some but not much), and via the air-borne sound waves (water too if you listen underwater ). All vibrations are forms of mechanical energy. Even the earth itself vibrates (at 1 - 2 Hz, well below what can be heard).Objects that are less massive (smaller and/or weigh less) can vibrate more easily and at higher frequencies. Stiffer materials are less prone to vibrate. And objects that are more flexible in terms of how they are supported (cantilevered like a diving board or simply supported like a coffee table) will vibrate at lower frequencies (which counter intuitively takes more energy which is a good thing). So you'd like your stereo system to be made of massive/stiff/flexibly supported objects. Microphonics describes the effect on the sound from small vibrations (typically in electronics). This happens mostly from air-borne sound waves (the louder the worse) on exposed tubes (which are all mounted as cantilevers). But it can also be easily heard from CD players due to their own self vibrations (which is why many audiophiles will add weights on top of the player). Unfortunately foot steps or very loud sound waves (mechanical vibrations) on soft wooden floors can be heard via turntables. This makes sense when you realize that vinyl playback is premised on a stylus vibrating as it tracks the grooves in the record.But most vibrations relate to the speakers. Since driver cones, domes, and diaphrams vibrate in and out, there is as much energy being imparted inside the cabinet as outside. As most cabinets are wooden (relatively not stiff material) and not terribly massive they vibrate much more than you might know (some generate more sound pressure than the drivers themselves). So this is a real issue for speaker designers. The best way to avoid this coupling to the floor is to use headphones. The 2nd best way is to float the speakers above the floor (magnetic levitation, hanging the speaker from the ceiling, or use pillows).
