Vibration dampening

I use springs under mine ( a hint from millercarbon)  I also pull them out from the wall about a foot.  I feel the bass is tighter and less boomy.  A set of isolation springs was less than $30

I too use the springs under my sub and works well, about a foot out yes.

Primacoustic Recoil Platforms are under both my speakers and subs.Their purpose is is to address floor vibrations.

All subs vibrate

thats what low frequencies do

save your money 

Iso 200 sub. Zero vibration in my setup.