When Is More Subs Better?

[shotokan_teen]

I have around 4000 watts (for now) to play with. I am looking at either 4 Fi Q 15's or 2 DD9515G. Obviously, the DD will handle power better and probably hit harder because of more power to each sub. But the FI would have more surface area.

When is more subs (with less power to each) better than fewer subs with more power to each?

[wfeld]

what about 2 fi bl 18"

[95pimpalass]

I say 4 15'' fi Qs would be louder still if u can give all four of them a clean 1000wrms over the 2 15'' DDs that would see say 2000wrms each