Pardon me if I oversimplify, but some underlying principles before I comment ...

In most subs, you have one or more drivers pushing air in large amounts at low frequencies. Unless you have perfectly matched multiple drivers arranged to produce exactly the same motions in a way such that they cancel each other out within the frame and cabinet of the sub, there will be a moderately complex set of equal-and-opposite energy reactions that result in vibration of the non-driver components. Some of this extraneous vibration energy may transfer to the air, some will travel into other objects via whatever ‘feet’ there are. Other than what is lost to friction/heat, the mechanical vibration energy MUST go somewhere.

There are two simple extremes to handle this vibration. One, the cabinet’s vibrations are almost totally isolated from the floor, usually by something with ‘give’ in it. Two, couple the cabinet solidly to something that dampens the cabinet vibration. A third ‘hybrid’ option is to couple the cabinet to something that dampens the vibration while isolating both the cabinet and the dampening mass from the supporting environment.

In case one, extraneous vibration of the cabinet will transfer some additional acoustical energy into the air directly. The type and size of cabinet will determine whether this is detrimental or nearly inconsequential. Spikes are an instance of the second and third situation. Much like a bridge on an acoustic string instrument, this small device will facilitate, not hinder, the transfer of mechanical energy from one object to another. That is why the cabinet will vibrate less – the spikes have allowed some mechanical energy to be transferred somewhere else. If the object on which the spikes rest can act as a somewhat efficient sounding board, the mechanical energy transferred will become acoustical energy. Spiking the sub to ‘brick,’ or other material that resonates poorly at the frequencies concerned, on top of ‘pad,’ with some give in it at the appropriate frequencies, perhaps in multiple layers for various frequencies, is a principle used in both some DIY and professionally fabricated products.

I have ‘sound board’ wood flooring, so I make some effort to isolate my loudspeakers from the flooring. I am not into expensive, exotic solutions, however. Why? Even if I were able to completely dampen, isolate and prevent loudspeaker mechanical energy from directly reaching the potential ‘sound board’ surfaces in the room, these surfaces will vibrate once affected by the vibrating air. Room acoustic treatments are another topic.

Sorry for the long-windedness. Put reasonable effort into solving problems you find, but then sit back and enjoy!


[This message has been edited by bestbang4thebuck (edited November 11, 2003).]