There are two reasons for going with multiple subs :

1. Getting more bass capacity than you can get out of a single sub.

2. Room resonances (modes) often give you uneven bass response, and even worse give you different bass response at different points in the room. Having multiple sound sources helps... generally you would have the two subs in different parts of the room for best results.

Reason #1 tends to be related to room size; larger rooms need larger subs and eventually you hit the limits of what a single sub can do.

Reason #2 is largely independent of room size; often small rooms can have worse response curves than large rooms.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
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