I thought the Monolith would have been a good cost effective upgrade. Perhaps more in power & depth of bass but not so much in quality?
I dont often disagree with Ian, but I will on this one.
Offering a whole 12dB of extra output at 20Hz, with 50% less distortion at the same frequency, plus a response flat to 18Hz against the SB12s 26Hz, the difference isn't in the least bit subtle and a clear demonstration of big box superiority when it comes to effortless reproduction of deep bass.
The Monolith also offers cleaner output at every frequency and volume beneath 50Hz too; It is a better sounding sub and the more you turn it up the wider the gap sounds. For the likely £100 outlay (after flogging the SB12) it would be an extremely cost effective upgrade and better than any SVS with music up to the 13Us.
You can clearly do better than both subs yet mentioned, but it costs. The B1 (the pick of the B Series) is a very nice sub with a very high standard of finish and well worth a long hard look, especially if you're looking for something to underpin the FB1s with music that is reasonably discrete in terms of size and add a dollop of low end over what you've already got.
That's not to say the 13Us aren't good with music - they're easily SVS's best music subs yet because the same set of criteria that satisfy good movie reproduction, satisfy good music reproduction. No, it's that their awesome room wobbling movie ability (and this is
way in advance of the B1) comes with a significant size penalty and the finish and detail is relatively basic to hit the aggressive price points they occupy. Again, it's not bad (but it's not REL), but there is a lot more of it to look at!
For pure movie use without compromise, the 13Us are a no brainer, but if there are other considerations, they're not the only answer.
Russell