I started out some years back replacing the spikes on my Thiel speakers with springs. I bought big butcher blocks for platforms and bored holes to hold the springs. I used four 48 lb/in springs per side to get a Fn of 3 Hz. The travel was limited by having the springs in the pockets of the platforms. The resulting change in sound on my suspended floor was dramatic. Using an accelerometer I could see effective isolation down to 3 Hz. And don’t worry, the speakers drivers do not have enough mass to make the speakers move in reaction to their motion.
After about 9 months I decided to buy and try the IsoAcoustics GAIA feet. Pretty expensive but I found my speakers sounded better with the GAIA. Surprisingly, the GAIA feet do not isolate the speakers from the floor as well as the straight springs. I kept the GAIA but put my spring platforms under my subs. The subwoofers sound amazing being perfectly isolated from the floor.
When I got my Wilson Sasha DAWs I used the Wilson spikes. The DAWs energize the floor, the walls and the furniture. WOW are they powerful. I bought the big GAIA footers and tried them on the DAWs. They firmed up the bass and improved imaging. Very expensive footers to support the weight of the DAWs but I kept them- didn’t want to go back to the spikes. Wilson says their new isolation feet work better than the GAIAs but they are double the cost.