Carpet and Floor standing Speakers?

You can go a couple different ways on this depending on your room. If you would like to couple the cabinets to the floor, then you will need narrower spikes with a more tapered tip to puncture through everything (carpet, pad, vellum) and rest firmly into the concrete. This can help the floor to help reproduce lower frequencies than the driver/cabinet is able to under it's own area. This is "transducing" with your floor helping. This is most noticeable on subfloors or other materials as concrete has greater mass.

If you have the sub setting on carpet (and subsequent pad beneath) then the cabinet is isolated from the flooring... this can tighten bass but loose much of the lower frequecies generated by using surfaces as attached transducers.

A nice amplifier with good power across the spectrum, good speaker placement, room treatments and proper use of parametric EQ's will make most of these differences null. The only thing left is the "tactile" feel of having the sub coupled / attached to the flooring spreading to nearby walls... frames... walls.

Setting speakers on carpet may or may not affect anything depending on Proper EQ and room placement / measurements / volume.

Moving the speaker a foot may have more of an impact than the footers... just depends on more factors than a simple fix.

Hope this helps!