Has Anyone Tried Nobsound Springs Or Other Isolation Devices Below REL Subwoofers?

Yes, have them under both my subs. Tighter and less bloated bass and nothing rattles in the house. 

Thanks for all responses. I’ll attempt to try it myself when I receive the sub. Just thought of asking here beforehand.

Missioncoonery - Three S510s? Wow, that sounds awesome. Unfortunately my room can only accommodate 1 due to space limitations. Current budget does not allow more than 1 anyway.

By the way, the manufacturer does not always give proper advice as I have found out. I own some Harbeth speakers, and the manufacturer/designer advised that the amp does not matter with their speakers as they will all sound the same. If I followed the advice about 13 years ago, I wouldn't have the Harbeth in my system today. 

My S/510 was extremely overpowering my room until I took the advice of a few ppl and moved it out of the corner and put a thick granite slab under it…bingo, problem solved. Soon as I move to a new joint I’m adding another S/510 to my rig, these things are incredible.

I tried a quadratic array of Nobsound springs under a REL T/9x, and it did not result in sound preferable to the stock configuration regardless of the number of springs per footer.

I’m aware REL does not recommend isolation, however, my s/510 sounds less boomy & more focused on a Townsend Seismic Podium. I much prefer this sound than resting on carpet.