what do you put under your sub?

I have two solutions. Under my VSA sub in my HT room, the sub which is a downshooter sits on spikes on a 2" maple block from Mapleshade. The block rests on four (4) Isoblocks (cork and rubber also from Mapleshade) which rest on the floor. This is a suspended wood floor which is hollow underneath since there is no slab. Bass is tight and there is no boominess through the floor.

In my two channel room upstairs, the MJ Acoustics sub (also a downshooter) sits on Nordost spikes, which in turn sit on an Auralex SubDude. Check this out, Auralex developed this design for roadies to use to isolate their speaker cabinets from hollow temporary arena stages. Inexpensive and very effective - bass is tight and there is no annoying thump through downstairs.

I have ASC Subtrap under my Velodyne DD-15.

Depends on your floor (and what you're trying to achieve).
If you have a suspended wood floor, and you want to hear the sub's bass output, not the room and floor rattling, use something that isolates. The Auralex SubDude is a nice option. A cheap, but not quite as effective, alternative is $1 hockey pucks. And then there's everything from isopods to sandboxes.
If you want to hear your room rattle and feel your chair vibrate, as some ( esp home theater guys) do, then couple the sub to the floor with spikes, etc.

If your floor is concrete slab, then the effects of either won't be as pronounced, and I think most find cones appropriate here, though isolation has been said to reduce floor vibration a bit here too. Again, depends what you want.

I've tried the pucks and DH cones and Pulsar points and even Aurios under my RBH subs. They all helped in slightly different ways, but I'm using the inexpensive pucks at present. I may try the SubDude next. Then again, I like bass that's extended and tight and non-intrusive, and I also use a Tact to equalize and eliminate room nodes.

I had an audiophile friend over a while back and he thought my bass was anemic. He didn't like it. The bass was too flat. Me, I thought it sounded great, but it takes a while to get used to flat bass as we're so accustomed to the extra room-induced boom.

I have various subs throughout from M&K to B&W ASW800(matrix series), to Sunfire True Sub to Onix Rocket UFW-12. Initially, they were on orignal spikes or rubber footers. I found that with spikes anchored to their little dimpled footers over on hardwood floors, the sub tends to dance around w/ heavy bass passages and aren't fast or clean enough.

Subsequentedly, I experimented with a 6" Lovan Jazz speaker/sub stand and that was the end of all of my bass complaints. The bass notes were much more faster, bass overhand(mechanically induced) were reduced drastically and were able to blend much more seemlessly with the rest of the speaker set ups, be it stereo or HT as if the bass modules aren't there--sonocally undetectable until the presence of bass signal.

Lastly, I tried a nice Osiris stand w/ sand-filled (weighing over 75 or 80lbs) w/ my UFW-12 and it was good though more costly than the Lovan. Didn't feel like making a comparison w/ Lovan as the darn sub weights close to 140lbs. All in all, a good stand is absolutely necessary if you want clean, punching and F-A-S-T bass that starts and stops on a dime. Experiment with what works best in your application.

Good luck and have fun!

Ken

WOW! a lot of great replies..thank you all. Ive got a Rel sub connected via high output connection with speakon neutrik connector to my linn chakra amps. its a 2 channel system. Rel subs come with spike to screw into the feet, but odly enough the manual suggests Not using them. it integrates very well, sometimes seems a bit boomy/muddy. it sits about 8" from corner on carpet which is on top of slab...this is the ground floor, and no basement.