Spikes versus Rubber on wood floor?

Mt thats an interesting suggestion. I like the sand part as it should not transfer vibration and the price is right

Markphd Thanks for the reminder I will look up the old thread

Chadnliz -Thanks for the encouragement- its an expensive experiment for me but finally getting to listen to great speakers with great equipment ignited a lust for improvement and you have to start somewhere.
Thanks everyone for the suggestions which fairly clearly eliminate rubber products. The joist supports on 12 inch centers were designed to have a large grand piano placed anywhere with no support underneath for a 30 foot span, so the floor feels completely rigid to the jumping test. I had not heard of the black dots - looks to be an intriguing material.
I have some cermaic tile pieces about the size of the speaker bottom, may compare the stock spikes on these to the balck dots.

Nsgarch - Got it, if the speakers do not rock back and forth over a single joist, they will rock better on the music.

MarkPhd Thanks for your input. I have been scanning threads for awhile but found them confusing, particularly when you add in the different needs of different components and types of flooring, so I thought I would post just for my speaker application.
Frankly I still am confused. I guess there is no clear consensus of spikes versus Tenderfeet type cones. It would seem to me that spikes if they are indeed able to draw out vibration from the cabinet would then vibrate the wood beneath and the adjoining spikes would act as a megaphone and transmit it back to the cabinet. Yet any type of soft rubber would allow the cabinet to move (jiggle). It leaves me wondering why something that is more inert and sound insulating yet not metalic such as styofoam would not work better.
WTB do you know who sells superspike?

Obviously even well constructed speakers vibrate or spikes would not work their way right through pennies placed underneath them.
Given all the divergence in answers, I decided to approach this logically through a hypothetical example. Please tell me where you think my reasoning is correct or incorrect. Lets say we place a vibrator on a kitchen table when the kids aren't home. In my example the vibrator is equivant to a speaker.
We turn it on (turn about is fair play). What will it do? It will clatter. This is equivilant of a poorly coupled speaker. Then we press down on it adding weight. Now it is coupled to the table and the table will act as an amplifier of the vibration - rather the disipate, the noise will get louder, true? This would be similar to a coupled speaker interacting with the wood floor. The speaker is now less vibratory but the table is magnifiying the sound.
Next we place an inert substance such as styofoam, sand, or rock between the vibrator and the table. We now get less noise. This suggests to me the best is to firmly couple the speaker to something rigid enough to reduce the speaker's vibration,and under this have something non-resonant so that the vibration is not passed to the floor.