Spikes or Spikeless

Speakers with four feet are a PITA. For all my previous speakers, I had custom Sound Anchor stands made, and those guys know the benefit of a three foot base. There is no need for the constant adjustment. My current speakers came with Sound Anchor bases the manufacturer has made for them and unfortunately they have 4 feet. Fortunately, they are easily adjustable and lock into place, but still I find the need to occasionally go back and readjust, maybe because the spikes are drilling into the concrete just a little over time under the over 100lb weight. If you have an option, and you can make the speakers stable with only three support points, IMO that is the way to go. As to your question, I have tried SA cone coasters, Audio Point cups and spiked directly into the floor on my carpet over concrete and I think spiked is best. On hardwood, I like coasters or cups with Herbies Big Fat Dots under them.

How heavy are your speakers? How thick is the padding and carpet? Have you tried your speakers with and without the spikes?

I also have a basement floor with carpet and padding. Over a 6 mo. to 1 yr. period I tried various combinations of spikes, wood plinths, rubber or composite footers, and nothing. This was for my VSA VR-4jrs. The worst was spikes directly through the carpet into the concrete. Grey, harsh sound with severely attenuated bass. What I finally settled on was a pair of custom maple platforms, 1" thick and about 2" extending beyond the speakers' plinths. Speakers spiked into the platforms, platforms spiked into the concrete thru the carpet. Got back my mid-bass, balanced out the rest of the spectrum, lost the harshness on top. I went with 4 feet on both sets of spikes but I have no doubt 3 would be better; also a 2" thick maple platform would probably be superior too. The platforms elevated my speakers a bit but luckily this did not cause problems re tweeter height and so forth.

I'm not sure what the objective is. Spikes are usually needed to decouple speaker from vibrating floor (infinitely small point cannot transfer energy). Your floor is concrete and most likely won't vibrate, so I assume you want to suppress speaker resonances. In that case you should couple speaker to the floor - either by direct placement on the carpet or on heavy base (thick marble or granite).

Spikes couple and allow vibrations to transfer. I realize that many theorize that spikes decouple by reducing the contact area between the bottom of the speaker and the floor. The reality is that the small contact point creates a very large psi value that in effect bolts the two components together. Vibrations travel very easily through spikes in both directions. Spikes are used with speakers to create a stiff, no rocking stance. All speakers are not the same so many times you have to try different things to find which works best for a given situation.