06-08-12: Mateored
Interesting. I need to do more listening. I think I might experiment by putting some weight on top of the sub to damp the movement a little. I've heard people putting bags of lead shot on top of subs.
Several years ago I got a fairly inexpensive 1x10 powered sub. I felt it could play cleaner. I had a slab of granite I had gotten from a Tandy store (just $20) for leatherworking. I placed the slab on the subwoofer (with a layer of shock-absorbing shelf liner in between) and voila! It made the bass much cleaner and more linear-sounding.