The term "speed" is a pet peeve of Legacy guru Bill Duddleston. He said in an interview something to the effect that if "bass was faster, it would be treble." I'm guessing that when a person says a sub is "fast" or "slow" they're unwittingly describing room interaction or the phase being very out of step with the mains. Not all subs have phase controls, either.
At any rate, I'd take a good small sub to a bad large one any day. A good example I can give concerns two subs I had years back. I had a Cambridge Soundworks sub, sealed with an 8" driver. The subs was very clean & tight, and could go quite low (you get some room gain at the low freqs, but it's of course room dependant), althought it would bottom with a loud CLACK if you pushed it to high volumes. In contrast, I also had a 15" Advent sub (with a Sunfire amp). Only reason I bought it was morbid curiosity. It was being closed out for $150. The thing was a total POS- the enclosure was very thin partical board with pretty much no stuffing/damping! A rap on the top with your knuckles was like smacking a cardboard box! It would put out a lot of sound, but it didn't go terribly low and the bass was incredibly loose: it was the very definition of boomy. EQ couldn't help, nor was placement the problem.
Of the two, the Cambridge was much better (I actually returned it and got the sealed 12"- it was a superb sounding sub, but alas, it died on me some time later).
That said, a few years ago I bought a pair of Hsu TN-1220's, and I couldn't be happier. I've owned many subs over the years, but once I bought the Hsus I knew I was done sub shopping.
Not that I'll
never try to upgrade...
