According to SVS the PB12+/2 has the PB13-Ultra beat for "output" for the first two tuning points due to it's dual drivers. But then down at the last tuning points is where the Ultra can beat it a bit.. So choosing an uprage.. It's been daunting, as there is so many great choices out there these days including Axiom...
It's not just about the output or low tuning but flat response as well and the PB13 is very flat, I haven't seen any FR graphs of the Pb12/2. I know the PB12-nsd has a bit of a bump in it's FR around the 50-60hz range which I found annoying.
