The 7.2 spec is for a 2 channel (stereo) subwoofer not double the amount of sub. I have seen that you don’t necessarily “overwhelm” yourself with bass, but it becomes muddy, boxy and/or unpleasant if not throttled or tuned/phased properly. Also the problem that I have every so often is that when the ability to severely augment the standing wave at the subsonic level is present, it can have a canceling effect, where you get less or nothing. So too much bass can go past being unpleasant and just plain cancel itself out. You will need to find that “happy medium” of the room and work with it to get optimum bass which may not be as much as you would like due to the fact that the room many not be able to accommodate your wishes. More speakers is not always the solution. But this day and age technology and the newer ways of baffling sub cabinets can produces killer bass with very little. It just takes the right kind or setting thereof. Not more speakers. But . . . . personally I love bass that can stop your heart and love my Klipsch MCM W Bin with two 18” Horn Loaded Cetec-Gauss drivers. Now that’ll stop your heart . . . break windows . . . crack concrete . . .

To clarify the last post is wrong. Low frequencies don’t have modes, small rooms have nodes and these modes are the result of soundwaves that interact with one another.

Room placement is also very important and there are two ways to compensate for low frequency problems when employing room placement techniques; move the seating area to a position where the seating is in between the peak and null points of the modes (you can determine this in an scientific, but effective method of walking around the room to find spots where the bass is louder) or you can move the sub to different positions within the room until a satisfactory position is found.

If more bass is required the sub can be placed in the corner where it can get boundary reinforcement from the two sidewalls, the ceiling and floor. This type of placement can add as much as 18dB increase in output.

Second subs are added to a room to smooth out standing waves (soundwaves that meet at their 1/4 point). Usually two subs are employed opposite one another or in positions parallel to one another.

The perfect scenario for a room using multiple subs is the use of four (to create identical mirror points).

In a small room there are many cases where one sub is enough to effectively handle the low frequency requirements in a home environment, especially when EQ solutions like the Audyssey technology is used in conjunction with a basic home theater system.

I’m afraid he’s wrong about 7.2 not necessarily being better, and the additional subwoofer would not be overwhelming as long as the sound is balanced properly.  For example, if the level was reduced to near zero, would two subwoofers overwhelm?  That demonstrates the error of that claim. The comment about the second subwoofer helping reduce nodes is correct; low frequencies have nodes, which are a real problem that is not fully addressed by placement.  The fact is that the MORE subwoofers, the less the effect of nodes. Of course, the sound needs to be balanced with the rest of the speakers as I noted.  A simplistic analogy would be one sub acting like one pebble tossed in a pond - the waves act like nodes.  Then drop two pebbles: the waves will be a bit more diffuse, a good thing.  Toss 10 pebbles; the waves will be much more diffuse.  Of course, the hit of even a second subwoofer is actually on the pocketbook, otherwise, its all pluses for sound..

Here’s a different approach., a midbass woofer.  You didn’t mention the current sub that you’re using (or I just missed it).  Depending on the low frquency extention of your current subwoofer and the crossover point of your main speakers you may be able to fill a hole in the secnd octave.  HSU research offers a midbass woofer to handle 40 Hz to 80Hz allowing the subwoofer to handle 20 Hz to 40 Hz.  The reviews I’ve read claim that it makes an astonishing difference in the impact of a surround sound system.

Get another sub.  Put against the wall that is 90 degrees from the your current sub you have now.  You have just eliminated most of the wave nodes in the room.  Also try to keep them out of corners(with two subs you will not need the “corner loading”).