JL Audio 13.5” Subwoofers

There's no replacement
for displacement. 
13W1v2 can move 64% more air than a 12W1v2.
13W3v3 can move 54% more air than a 12W3v3.
13W6v2 can move 69% more air than a 12W6v2.
13W7 can move 39% more air than a 12W7.