>>>I understand that adding a second sub can cause cancellation in certain areas of the room, even if one is wired or switched out of phase. This can be corrected for by moving them around, shifting phase, etc, but there will still always be some cancellation somewhere.<<<
That's very likely,but only if the subs are placed apart from one another. If someone wants to increase the headroom(or lower distortion for
a given volume),than adding a second identical woof, and placing it near the first will give you a 5 to 5.5dB increase in potential volume...with no additional *cancellation* issues to concern yourself with.
If you placed 4 subwoofers very near one another, they would for all intents and purposes...interact with the room boundaries as one large
>>>Would it not be smarter, since subs are nondirectional, to pick ONE AND ONLY ONE sub which is big enough to drive your room? That is of course not considering things such as budget and space constraints, etc, this is strictly from a performance perspective.<<<
Ayup. Very often...a single POINT SOURCE for bass leads to the smoothest bass response over a variety of listening positions. Now--a single *point source* could be ONE enclosure,or it could be a half dozen enclosures tightly packed in a good corner.
I'm probably splitting hairs little here(if so, I apologize)...but there's really very little *downside* to adding additional bass headroom in someone's HT. In fact , I'd guess the majority of HT enthusiast are "bass-shy" if they like to listen to DVDs anywhere near reference levels.