For years, I put up with boomy, one-note bass from a Def Tech PF15 in my combo 2-channel/HT system. Thanks to this board, I have added both a Paradigm X30 sub controller (for level and phase adjustments) and a Behringer 1124P FBD Pro with parametric digital EQ. The results after tweeking the Behringer were dramatic. Properly used, notch filters can turn a mediocre sub into a good one.
That said, I have since added a pair of Vandersteen 2Wq subs to my system, to augment the mains (Vandy 1C). What I have learned from this upgrade is that if you start with a good design, DSP or notch filtering is not as critical. With these subs (which have adjustable Q), blending with the mains (at least in my case) was easy and seamless. Bass is quick, taught, musical and powerful. There is no bloat, boom or sense that the sub is there at all; everything seems to come from the mains. These subs sit in corners (they are designed to be placed in corners), and my room is pretty lousy from an acoustic standpoint. Again, the difference is in the engineering. Richard Vandersteen looked at how most consumers will use a subwoofer, and designed it appropriately. More than just putting a big cone and an amp in a box. That's my $0.02 - YMMV.
That said, I have since added a pair of Vandersteen 2Wq subs to my system, to augment the mains (Vandy 1C). What I have learned from this upgrade is that if you start with a good design, DSP or notch filtering is not as critical. With these subs (which have adjustable Q), blending with the mains (at least in my case) was easy and seamless. Bass is quick, taught, musical and powerful. There is no bloat, boom or sense that the sub is there at all; everything seems to come from the mains. These subs sit in corners (they are designed to be placed in corners), and my room is pretty lousy from an acoustic standpoint. Again, the difference is in the engineering. Richard Vandersteen looked at how most consumers will use a subwoofer, and designed it appropriately. More than just putting a big cone and an amp in a box. That's my $0.02 - YMMV.