Btw - I found an explanation on AudioAsylum from Brian Cheney which says spikes do both, depending on the frequency...
http://www.audioasylum.com/audio/speakers/messages/40070.html
AhHA!!
I can see this is going to get confusing, since the term "couple" and "decouple" is being used to describe TWO types of physical relationships.
First coupling seems to be describing the mechanical bridge between two bodies that cause that bridge to take on the mass of the the other depending on the "degree" or quality of the coupling.
The Second Coupling (and I think the one Big B is refering to) is the proximity of the frontal plane of the speaker is "coupled" in an unbroken plane with the floor (as in there is no "gap" if the speaker were set up on spikes).
These are two different "couplings". Brian's post actually addresses both of them and if I'm not mistaken, many times people just "set" the speaker on cones which made both couplings a problem.
Brian can jump in and clairify if nessessary, but I think the larger problem of "decoupling" from the floor (and in this case it means lifting the speaker up so that the Sound Pressure travling down the frontal plane of the speaker, from the woofer, would encounter the "decoupled" GAP and would lose some of its steam.
Now in reading the thread, it seems that B, felt that cabinet vibration would smear some sonics, by introducing them to the floor. I have to assume he was talking about a wood floor.
This thread was from 2000. I think B, has modified his stance on that a bit. While he still doesn't advocate spikes, since they still (in most cases) cause the "planar decoupling" of the front of the cabinet with the floor, he now, on accasion, will add "mass" to a sub to reduce reactive resonances, by sheer mass increase and this mass will also increase mechanical coupling acheived by adding that mass.
In fact at CES last year the 65# Ampzillas were called into play for that duty on the 215 SUBwoofer, since it was creeping all over the place on the carpet.
So I hope that is clear. There are two types of couplings
1) the mechanical coupling of an object to another for purposes of adding mass and reducing suceptability to deleterious vibration or resonance.
and
2) The "planar" coupling or joining of two surfaces to provide an unbroken boundary for the sound pressure of bass frequncies to travel more effectively.
Wow, I hope that is not confusing
