I still read, very often, all those things about "fast bass" and how it is needed to have "accurate sound". Most refer "tightness" as the ability of a driver to quickly shuts up after a punch, supposedly, this "speed" will make a good sub because of the good definition on bass frequencies. Of course, this "sounds" right, but is a just a myth. If a driver is not able to start and stop fast enough it won't play certain frequencies. It is as easy as this. So, there is nothing such a "fast" or "slow" driver. The boomy (or sloppy) sound of some subs has more to do with their "Q" (how fast the slope of their cut frequencies act), the room in which they are located, the exact position in the room, and, lastly, with its harmonic distortion than with its proposed "speed".