As the subject asks, what is the typical frequency where bass cancellation (super crests, troughs) from multiple sources becomes a real issue for music? The consensus seems to be that bass management is a really great thing for this, and running a single sub is better than multiple subs placed around the room (the exception being multiple subs stacked). This seems to be less of an issue for higher frequencies, since people don't discuss it much here, so I assume there's a threshold where it becomes an issue. What would it be? I expect that room dynamics will affect the answer, but, if you were to generalize... Thanks, Martin.