@avanti1960 @audphile1
Spikes!!! Quite right! I entirely agree.
Key points.
First order objective. Prevent the speakers vibrating to the music.
Second order objective. Prevent the speaker chassis from vibrating in response to the moving parts - cones, etc and other in-room vibrations.
Those who have concrete floors are fortunate. More fortunate still if it is a concrete screed laid directly on footings on the ground. Spikes are mandatory. If the speaker is heavy enough (weight it if it's not) spikes prevent all movement of the speaker chassis. Thus what you hear is only the movement of the cone etc and not cone movement inherited from chassis movement (better known as distortion).
Some people say the vibrations of planet Earth will affect this set up. Phooey. Such vibrations are FAAAAARRRRRRRRRRRRR less then in-room in-home vibrations permitted by flexible footers.
None of the above applies where speakers are not standing on concrete, where flexible footers are a necessary compromise solution.