FWIW,
My own experience would suggest a few things, all of which have already been mentioned, but none of which may be clear from the debate:
If you lack bass management software in your system, an array of four optimally placed subs is likely to provide significantly smoother bass response at your listening position than an optimally placed single or dual subwoofer set-up. If you DO use bass management, the delta in performance between more subs and fewer subs at your primary listening position is likely to be smaller. IME (and I did try a decidedly poorly controlled A/B comparison at one point), a single (or pair of) bass managed sub(s) may well provide smoother response than a quad array of non-managed subs at the primary listening position.
However, you may still have smoother response over a large listening area with a "non-managed" quad subwoofer array vs a pair of managed subs - since bass management software IME optimizes response in a smallish window. As to optimal placement of such a quad array, you're on your own. Expert opinion seems to vary, so - if you end up with four subs - you should probably experiment with both in-corner and non-corner subwoofer placement to determine which sounds better.
As a practical matter, for a 2 channel, music only system, bass management software is still rare. In this case a quad array is likely to be the better choice. Once you introduce bass management software, the incremental value of additional subs is less dramatic. Of course, everyone has their own particular sweet spot on the curve of diminishing returns.
Since you're using an HT system, it's likely that you already have bass management software. If that is the case, the primary advantage of adding additional subs is the incremental gain in clean output capability at any given frequency. Even the best subwoofers' distortion increases dramatically with SPL at very low frequencies (tho the best models offer mighty impressive performance in this regard). A single monster - like the 1812 - may provide more than enough output for you. Still, two 1812s will get you more. So, in this respect, (assuming the use of identical subwoofers) more subs are better than fewer subs. But IMO, the real question here is.... overkill. How much clean output capability do you really need?
Well...,
How loud do you listen?
How big is your room?
How deep is the is the lowest frequency you care about reproducing cleanly?
IME, I'd say that a pair of high quality, high output 12" subs (SVS, Rythmik, HSU, etc) probably does the trick for most listeners in most HT rooms that have bass management systems. However, it's just not possible to say with certainty that it will be enough for you. You can always start there and add more if the need arises.
Good Luck,
Marty
My own experience would suggest a few things, all of which have already been mentioned, but none of which may be clear from the debate:
If you lack bass management software in your system, an array of four optimally placed subs is likely to provide significantly smoother bass response at your listening position than an optimally placed single or dual subwoofer set-up. If you DO use bass management, the delta in performance between more subs and fewer subs at your primary listening position is likely to be smaller. IME (and I did try a decidedly poorly controlled A/B comparison at one point), a single (or pair of) bass managed sub(s) may well provide smoother response than a quad array of non-managed subs at the primary listening position.
However, you may still have smoother response over a large listening area with a "non-managed" quad subwoofer array vs a pair of managed subs - since bass management software IME optimizes response in a smallish window. As to optimal placement of such a quad array, you're on your own. Expert opinion seems to vary, so - if you end up with four subs - you should probably experiment with both in-corner and non-corner subwoofer placement to determine which sounds better.
As a practical matter, for a 2 channel, music only system, bass management software is still rare. In this case a quad array is likely to be the better choice. Once you introduce bass management software, the incremental value of additional subs is less dramatic. Of course, everyone has their own particular sweet spot on the curve of diminishing returns.
Since you're using an HT system, it's likely that you already have bass management software. If that is the case, the primary advantage of adding additional subs is the incremental gain in clean output capability at any given frequency. Even the best subwoofers' distortion increases dramatically with SPL at very low frequencies (tho the best models offer mighty impressive performance in this regard). A single monster - like the 1812 - may provide more than enough output for you. Still, two 1812s will get you more. So, in this respect, (assuming the use of identical subwoofers) more subs are better than fewer subs. But IMO, the real question here is.... overkill. How much clean output capability do you really need?
Well...,
How loud do you listen?
How big is your room?
How deep is the is the lowest frequency you care about reproducing cleanly?
IME, I'd say that a pair of high quality, high output 12" subs (SVS, Rythmik, HSU, etc) probably does the trick for most listeners in most HT rooms that have bass management systems. However, it's just not possible to say with certainty that it will be enough for you. You can always start there and add more if the need arises.
Good Luck,
Marty