Interesting thank you.
I had fun trying out a whole bunch of different isolation and coupling materials and devices underneath my loudspeakers. For much of it, I was able to carefully (measuring) maintain the same height of the speakers, just shifting in different layers of products. And I used a set of small furniture jacks similar to this….
…..underneath the speakers or underneath the platform they were sitting on, So that it only took a couple of pumps of the lever to lift the speakers and swap out a new footer or material, which made some pretty quick changes.
It was certainly fascinating how different materials and combinations appeared to alter the sound. For instance, when I had the speakers on a MDF or a granite base, if I put the base on speaker spikes (in this case low profile Isoacoustic carpet spikes) and then if I placed a hockey puck between those spikes and the floor, the bass would get tighter and the overall tonality would “ lighten” or brighten up. But if I reversed it, and placed the hockey pucks on top of the carpet spikes instead with the carpet spikes going directly into my wood floor, then the sound would reliably get a bit more rich and bassy, with a slightly darker overall tonal shift.
At least that was my reliable impressions anyway. I ended up always preferring some level of coupling of my speakers to the floor, which is why at the bottom of the base I have spikes going into the carpet/floor.