When it comes to subs, two is always better than one in terms of better and more consistent sound quality throughout the room, the caveat though it may take longer to get two subs mixed in optimally compared to one.
The more, the merrier in general, though with diminishing returns of course. Even 4 or more is not out of the question in some cases.
Once the bass levels are right no matter where you listen from in the room that you might care about, you are done.
If you listen from one location only, and bass levels are fine, then one sub may suffice just fine.
With one sub (ie no stereo), its more beneficial than otherwise to configure so sub fill in solely in lowest octaves that mains cannot handle otherwise in that sound becomes more directional at higher frequencies.
The more, the merrier in general, though with diminishing returns of course. Even 4 or more is not out of the question in some cases.
Once the bass levels are right no matter where you listen from in the room that you might care about, you are done.
If you listen from one location only, and bass levels are fine, then one sub may suffice just fine.
With one sub (ie no stereo), its more beneficial than otherwise to configure so sub fill in solely in lowest octaves that mains cannot handle otherwise in that sound becomes more directional at higher frequencies.