Under speaker metal SPIKES ...what is the point ?

Well first it ruins your carpet or hardwood floor. In theory, all the weight of the speaker being on a tiny little point increases the pressure on the floor at its contact point and better couples the speaker to the room and prevents it from vibrating or rocking in minute increments. That's what I understand is the theory. Does it make a difference? Who knows. It's like chicken soup when you have a cold, it can't hurt, except for the floor covering. Someone in Sensible Sound has explained that the physics of it all are somewhat flawed. Again, if the spikes are free and you or your significant other (what a terrible expression, I only hope it's politically correct, 'cause I sure ain't) don't mind the collateral floor damage, go for it. Maybe you will be able to hear a difference, I doubt it. I sure as hell have not, but hey, my ears are only gold plated.

Also bear in mind that the limited surface area at the tips of the spikes presents little surface area for the vibrations from the floor to travel up into the speaker cabinets or stands. The broader the surface area exposed to the floor the more likely the cabinets will act as floor vibration antennae. Added bonus - the spikes keep the speakers from dancing across the room.

Speaker spikes serve ascentially two purposes. The first being they provide a contact point w/ considerably less surface area thus increasing the stability of your speakers.

One might ask why is this important? Think of your tweeters speakers w/ small piston areas designed to move only a few thousands of an inch any movement of the cabinet will alter the sound.

The second purpose of spikes is to allow a focal point for resonance energy. That being secondary vibrations from the cabinet after the speaker initionally pulsates. By mating the spikes w/ the speakers this energy travels from the large part of the cone to the point (or moving from greatest resistance to least) in wich it is disopated into the floor.

Following the above thorough reviews regarding the physics of spiking speakers, I'd like to add some more commentary regarding the sonic advantages. I hardly consider myself to be golden-eared, but the changes wrought by spiking my speakers were anything but subtle. The entire spectrum became much more natural sounding, with an especially focused image vs. a previously somewhat blurred image. Staging was also enhanced; wider & deeper. Bass articulation & control was also significantly improved. This much improvement for so little $ spent makes spiking one of the most cost effective tweaks that I've ever undertaken, & I ask myself why it took me so long to do this when it was so easy & inexpensive. But just like upgrade cables & AC cords, I didn't really want to believe it until I tried it. Presently I'm using plated brass cones, but now I'm curious about trying out some different spikes, footers, even pods, in order to determine which ones (or a hybrid mixture of them) will provide the best results.

I think the bottom line is, try it, you'll like it.