Some months ago I posted on a thread about putting Herbies Gliders underneath my speakers. These gliders actually decouple the speakers from the floor rather than couple them.
But I have wood floors on pier and beam built in 1938 and the floors are a little spongy.
The 8 gliders were under 120.00.
The results were actually quite significant. The bass was much tighter, better defined but not overpowering. The mids much clearer and the imaging kinda jawdroppingly improved. I quickly saw I didn't need more bass traps after all.
Well, over on the Slim forums one very astute audiophile(Phil) from England had done much the same with his speakers on wood floors.
But he also uses digital RC and he had to recalibrate because the footers had changed some bass frequencies by as much as 3db.
So here was some objective evidence that this tweak has an effect.
Phil is redoing his floor again so he is going to remeasure with and without the footers to get a more complete idea.