You nailed it exactly. You can not isolate a subwoofer. Bass is extremely powerful. Play a 30 Hz test tone at 80 dB and walk around you house, go outside and walk around your house. The whole house will be rattling. Glasses on shelves, silverware in drawers, the walls, everything will be rattling, a symphony of rattles. And, there is absolutely nothing you can do to stop it. Fortunately, the loudest sound always wins and with the entire system playing the rattling is masked. Anything that is not masked is usually easy to find and stop. (like my movie screen)
SVS SoundPath Subwoofer Isolation Feet
I like to have these feet around to play with on various speakers/subs and I even put them under an AV cabinet. I just bought two new sets and noticed they’re SIGNIFICANTLY stiffer or "harder" than previous versions. Older ones are more "squishy". Has anyone else noticed this? It kinda shows me there was zero thought or engineering to them except to make something rubbery and bouncy and charge a bunch of $ for it.