Originally Posted by shadillac
Jim, for the size room I have do you feel I need 2 15"s or do you feel 2 12"s be fine?
Depending on how you set the room up, in my opinion, you'd be best served by two fifteen inch subwoofers placed near-field; on either side of the listening sofa position. One fifteen inch subwoofer driver has about the output of two twelve inch drivers so two fifteen inch drivers would have about twice the output (additional 3dB) of output. Irregardless, if the subs are place in corner locations, you'll get additional output; room gain. A sort of corner loaded free lunch.From Data-Bass,
here's a link discussing "room gain" that will give you more insight as to the benefit of subwoofer placement.
You have a long narrow room. Is this room open to any additional rooms? If open to additional space, if one is wanting full, deep, quality sound, you're going need more subwoofers. If you start with two fifteen inch subwoofers, you'll have a good start but to get where most wish to go, down the road it's recommended to consider adding additional subwoofers to help with issues that revolve around room modes and gain.
As to choices and what direction one should go, the number of Benjamins one has in their pocket will make most of their decision for them. And if this is the case, and there are but a few Benjamins to begin with, one should consider the best and largest single subwoofer they can invest in: no holding back. Buy a single fifteen inch subwoofer which expectedly will be placed nearfield and as soon as one is able, purchase a second, equal subwoofer with, due to your room size, an eye on additional subwoofers down the road.
(I need more power Scotty!)