Vibration dampening

it implies a few issues if the subs vibrate - it must sound "shaky". I wouldn't solve it by fixing whatever it is connecting it to the floor, I would eliminate the vibration. 

I have used Herbies products and I think you need to decide if you want to couple the sub to the floor or isolate it. I use Townshend Podium products to isolate my speakers from the floor (suspended wood) rather than coupling.  Isolation made a significant difference and for my application, they are a essential componet.

I have laminate floors.  My subs are on SVS Soundpath feet, then on a heavy travertine plinth, then on rubber and cork anti-vibration pads.  Definitely tightens up the bass. 

I have laminate floors and I also use the SVS Soundpath feet under my Velodyne DD 10 sub. In my case, the sub sits on a small slab of granite (19" x 16"), which in turn sits on a thin rubber mat of the same size. I am happy with the sound and even happier that my adjacent neighbors don't complain. Lots of good advice here, so best of luck with your particular situation. 

I have a floating wood floor that was not working well with my subs.  The subs were boomy and shaking the room.  I installed Iso Acoustic feet on the subs and the problem was solved.  I'm now very satisfied and you can't "hear" the subs in the system.