i would call it subwoofer isolation platform, but that is too upscale for my tastes. a few months ago i built a platform for my sub to compensate for our uneven floor so that i could level it out. i suppose one could say that it decouples the sub from the floor, etc., but my main reason for building was to keep it from being unlevel. i still dont know why velodyne would put a sub in the class of mine out with little plastic feet (i think they have changed this now though). i was going to mount adjustable screwed in feet into the sub, but for resale purposes (you never know) i decided not to. it cost me about $5 to make the platform which is the cost of the felt and glue. since i was using wood from an old bookshelf that was junk (wood was good though), i had to attach 4 pieces (2 parallel on top layer and 2 on the bottom layer perpendicular to the top). so i had a four board square. i then cut five circular holes through the bottom layer of boards (four corners and middle) so i could mount my recycled speaker stand feet. the adjustable feet had a aluminum head that a scred threaded into and spikes on the cones on the bottom, so i had to be able to rest the heads in the holes on the wood. i would take out the middle spike if i did it again, because it is too hard to adjust... after a few weeks of use and one move with all the spikes falling out i gorilla glued them to the stand so that now they are way easier to move and subsequently adjust. oh and i felted the stand with black felt (because its breathable next to my laquer finish on the sub, cheap, easy to work with, and decent looking). my sub weighs a ton, so i needed a stury platform. i just stapled the felt to the bottom of the platform out of sight, simple but effective. anyway i thought i would post something in this forum to validate its existence and possibly draw some other posts to it.