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

just wanna know if there is any ( i'm sure there is )
phisycal explanation for using metal spikes under speakers..
instead of using rubber or plain nothing ..

i would think it is to minimize contact level at maximum..
but what do you get by doing that ? :)

Speakers vibrate when they play. Spikes "couple" the speaker to the floor such that vibrations are shunted from the speaker and into the floor. This usually has the effect of tightening up the bass, which makes the mid-range and treble more clear. And as the bass is "faster" or more articulate, pace, rhythm, and timing are also often improved (PRaT).

Of course the effect depends on many things such as type of floor, type of music, how loud it's played, type of spikes, etc. The opposite of "coupling" the speakers to the floor would be using rubber feet or footers which usually has the effect of "de-coupling" the speakers from the floor.

De-coupling is more often used with other stero components such as pre-amps and front ends. And sometimes the two techniques can be effectively used together, ie McCormack amps do both-- they have a coupling spike at the bottom rear, and sorbothane feet at the front for de-coupling.

All of this has to do with vibration management, and there are many old threads on the subject. Cheers. Craig.
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.

Looks like that most people appreciate using the spikes !
I would like to try it myself !
However one question, how can add I spikes to my
original (not i-version) psb stratus gold, thanks !

p.s. BTW, is it a good idea to put a quarter under the spike
to protect the floor ?
As mentioned, spikes reduce the contact surface and form a more rigid coupling to the floor. A simple experiment can illustrate this--take a telephone book (the bigger the better). Slide it on a smooth surface. Then tape three pennies on the bottom and slide it on the pennies. Reducing the surface area increases the friction and makes it harder to move. As to the second part about disapating energy through spikes, the theory is correct, but I don't think in practical terms it is very effective. Disapating energy is best done with devices designed to do just that. I have a few of these made by Teknik (I think), but I don't think they work very well. The theory is they convert the vibrational energy into heat energy.

Why is coupling the speakers to the floor important? You increase the effective mass of the speaker. This is important for accurate bass reproduction (which intail effects the entire frequency spectrum). The bass driver in your speaker works like a piston moving back and forth. You may have heard "for every action there's an equal and opposite reaction" (I didn't make that up--Newton did). If the speaker can move about it will, and thus the force that bass driver is exerting is reduced by the movement of the speaker. If the speaker is coupled to the floor it can not move as easily, and thus the bass driver works more effectively. Not to belabor the point--there is still an equal and opposite reaction, but now the mass has increased as the speaker is coupled to the floor, so the movement is much smaller.

The effect of spikes will change depending (mostly) on a combination of speaker weight and the bass driver. Therefore a realtively large speaker with only 5 inch drivers will not benefit as much as either a mini monitor or a large speaker with a large (12 inch) driver.

In the end Argent said it right--try it,
I'd like to add a thought. Every comment above about using spikes to minimize vibrations and blurring of detail is 100% correct, and the minute I screwed spikes into the feet of my 200 pound speakers there was a substantial improvement. But then, on the advice of a dealer I trust, I set the spiked feet in Vistek Aurios Pro footers (round footers, about 3 inches across, with top and bottom plates which move independently of each other, probably on ball bearings), which decouple the speaker mass from the floor. The spikes rest in indentations on the top plate. If you tap the speaker, it will sway on the Aurios Pros. The effect in terms of clarity and detail is so astonishing I am in the process of buying Pros to go under every component in the system. (They do amazing things under turntables and transports also.) Skeptical? Try it, you'll be amazed.
Mgottlieb: That's interesting. I don't have a good physical explaination on why that works. The Aurios Pros should work well under almost any component, especially transports because it disappates mechanical energy that is undesirable. For speakers, the mechanical energy is what is needed--so why does it sound better under speakers--you got me. It goes against what I would have expected--but it wouldn't be the first time something in this hobby has surprised me. Anyone with an explaination on why the Aurios Pros worked for speakers?
Abstract 7--my best guess is that spikes cut down as much as possible of the speaker-floor vibration interface, and the Aurios Pros essentially cut out the rest, leaving nothing but the sound the speakers are outputting. Probably hanging the speakers from the ceiling would be even better, but a bit impractical for 200 pounders. (I'm sure someone out there has tried it, of course.)