I am reading where some companies are recommending more than one sub. Why? Is it to play the bass louder?
Two (or more) subs will play louder than one, but the main reason multiple subs are getting recommended is to achieve smoother bass response in the room. Although bass frequencies are omnidirectional and, in theory, one sub seems like it should be enough, in practice two or more subs placed strategically in a room work better.