Check out Primacoustic Recoil Platforms. I have them under each of my three subs.They work best flat against the bottom in between the feet.Not expensive and they're returnable No more rattles and tightens the bass significantly.
subwoofer buzz - how to eliminate it
MartinLogan Dynamo 700w
At low frequencies, it vibrates, like it wants to fall apart. It does have a rubber feet, sitting on a hardwood floor, what could prevent it? Isolation feet? More rubber? Also it's facing the floor but can be turned sideways, would that help?