One or two subwoofers?

Adding subwoofer to two-channel system. Main speakers are a MTM two-way design flat to about 45hz (Northcreek Catamounts). Hoping to get down to 25 to 30hz with subwoofer. Looking for fast, tight response to match main speakers. Subwoofer will be integrated through Tact room correction pre-amp with sub-outs for up to two subwoofers. Room is medium, about 10' x 17'. Have read elsewhere that two subwoofers are best. Is this true and, if so, why? I thought low bass was non-directional, so no loss of stereo effect by using one. I'm willing to crowd the room with two subwoofers if necessary for best effect, but would prefer just one. Your thoughts? Thanks in advance.
Hello Lavoy,

If sound quality over a large listening area is your top priority, consider using two (or more) small subwoofers. This will not give you the loudest deepest possible bass for your dollar, but there are acoustic issues that can be addressed through multiple subs that cannot be addressed with a single sub.

In my opinion, room acoustics is a dominant factor in low frequency sound quality, and maybe the most dominant one. Room acoustics may well play a much larger role than the relatively minor differences between one good subwoofer and the next.

By having two or more subwoofers positioned asymmetrically around the room, each sub's room-induced pattern of peaks and dips will be different for any listening position in the room. The net result will be smoother bass than what you could get from one unequalized sub. And equalization only works within a limited listening area.

For this approach, you want subwoofers that have a steep (fourth order) crossover so that you have placement flexibility - otherwise you may be able to hear the subs' locations.

I can go into more detail about this scattered multiple low frequency source technique if you'd like. I use it in a system of my own design.

I wholeheartedly agree with Duke. Some good reading on the subject is found here:

As well as elsewhere on that site. The documentation there leads to a very strong argument for using subs regardless of your main speakers’ ability to reach the lowest octaves. It all depends on your room, and the placement options for your mains and subs. It could be that the best place for your mains is not the best place for the subs, so the mains shouldn’t necessarily try those frequencies. Always though, this all depends on your ability to tune to subs properly to integrate with your mains.

In my set-up I was surprised that the speaker designer suggested simply orienting one sub 90 degrees in relation to the other. I tried a lot of positions that looked really nice, but this suggestion ultimately gave the best response. Maybe it was just coincidental, since I really didn’t have many placement options.
Build the Tact subs! if you are using a Tact 2.2x or 2.2xp... they are designed to work in this combination.

Otherwise I would say buy one high quality sub if you can't buy two high quality subs.. Crappy subs aren't worth owning.. nothing can fix what they can't do...