I've had a 15" L7 in a ported box that was great but my pair of 12"s move way more air.

 

I personally think 2 12" will be louder than 1 15 because of cone area. Generally, a 12" sub has a cone area of 113 square inches. So multiply this by 2.
113*2= 226 square inches.

On the other hand, 1 15" is 192 square inches.

So 2 12" have more cone area, thus moving more air

But the box plays a major factor. You could probably make 1 15" louder if you make a proper box

 

Whoa... what 12" sub has 113 square inches of cone area?? Must have some pretty thin basket and surround.

 

lol


maybe its has the invisible type.

i say 1 -15
but imho too many variables to determine that... you haven't even made a mention as to what vehicle its going into

but i figured as the name says... a dbking should already know this answer

 

build a really good box for 2 12s and then erpgrade subs n power down the road

 

my 2 kicker l5 12" in a custom ported box hit 145ish @ 36hz last time i metered it
amp v900xd rated at 1000rms at 14.4v 2ohm