Originally Posted by simple man
Why is that?
Normally, it will introduce phase cancellations when your main loudspeakers and subwoofer play the same bass frequencies. In the bass frequency region that are overlapped, they tend to become rather bloated/boomy sounding. Only your ears will tell you what sounds good, and if it's a problem in your room, with your setup.
Personally, with my setup, I tend to keep my sub in line with my LCR loudspeakers.
I've done a tremendous amount of experimenting and like what the "Plus" setting sounds like in my room.
Once I add another sub (or two), I will turn off the "Plus" setting.
I feel that it is better to have two or more subwoofers to begin with and NOT use the "Plus" setting at all.