I have a velodyne DD-15 and puchased a symposium svelt shelf to put underneath.I replaced the rubber footers with the svelt so the bottom of the whole sub cabinet rests on the svelt.What a difference without trying to listen.Clean bass just popped right out,almost as good as no sub cabinet,I guess you could say that most of the bass was freed up from from the physical part of the cabinet.So i replaced the spikes on my revels(50-as)with the svelts,For me I won't go back to spikes or rubber feet.I like upgrades or tweaks that you don't have to try to listen,They make you listen,I like surpizes like that,Hope that helps(it does for me).