The LM12As I have (apparently discontinued) are biamped; the PM12As (current replacement) aren't. I don't think that's a necessity or even necessarily an advantage for those cabinets. Is there a reason you consider it important? I've used both of these cabinets (the LM and PM series) and really don't hear a difference.
Regarding frequency response and SPL -- these are claims that, like "so-called power ratings" are often...uh..."optimized" by advertising departments. I've run basic frequency response analysis on about half a dozen of these cabinets (sine sweep, mostly) just to see what was there for EQing purposes, and the Carvins do far better than most of the higher-end cabs in that regard. None of them are flat, of course, including the far more expensive QSC K-series, but in terms of what you can get out of both the top and the bottom (with the bottom probably a bit more important), they're excellent. As for SPL -- note that the sensitivity ratings on the passive versions of the Carvins are very high, meaning that you'll get a higher SPL from one watt than you will on those with lower sensitivity ratings. Add to that the higher actual power available, and you have a louder speaker with lower THD than the competition. Was there something I missed?
