Originally Posted by grunt66
The short answer for wanting two subs is to even out the sound I am hearing from the sub. Presently the sub is to the right of me and I can tell the sound from the sub is to the right while listening to music. Hopefully by adding another sub the sound will be even and sound like it is coming straight at me. I do more listening to music (70%) then movies (30 %). The output of the Monolith 15 is great and I do not need more volume.
Okay, I understand! I'm also a little bit susceptible to bass localization, so I know what you are trying to accomplish. Well, if you like the sound signature of the Mono 15, and have enough output, but can't accommodate a second one due to the footprint, then I would probably consider a a pair of Rythmik ported subs. I would stay with ported in order to get the <50Hz and <30Hz SPL, and the low-bass tactile response you are used to.
But, I would consider a pair of Rythmik subs because they will have a sound signature that is similar to the Monolith's. The SVS subs will have a little deeper/thicker tone. Since you say that you are 70/30 music to movies, I might stay with the slightly clearer sound signature that you are already used to, and a pair of Rythmiks should be excellent for that.
My personal choice in this case would be a pair of FV15HP's. You might be able to get by with less, but I would always advise people to have more bass (and especially low-frequency) output than they think they will need, in order to avoid future upgrades. Two FV15HP's would give you excellent overall performance at a lower price than the dual PC4000's. They have a little bit bigger footprint than the PC4000's, but they are much smaller than the Mono 15.
They are 18" wide by 24" deep by 24" high, although the grille and heat sink on the back add another couple of inches. They can, however, be turned sideways if necessary. (They will operate perfectly well no matter which direction they are facing, just as the down-firing PC4000's will.)
That's my recommendation, and I would try to make that size work. Cabinet volume is important for low-frequency performance. But, if you decide that you still can't accommodate the FV15HP's, then I might give some consideration to the Rythmik LVX12's. Two of those might give you sufficient output in your smaller size room, although I do believe in some degree of overkill when possible.
I should also clarify the fact that I personally like the sound signature of SVS subs, but my use of them is exclusively for movies. I like the slightly deeper-toned subs for movies. But, where someone else is already accustomed to a slightly lighter/clearer sound, for a primarily music application, then I think it is wise to consider Rythmik subs. They are specifically known for having a lighter/clearer sound signature.
I hope this helps!