It doesn't surprise me at all that he finds the PB13 is more musical than the old PC12U. If you look at the base FR of the old PB12U from Ilkka's measurements (linked on post 3), you'll find that the response at 80Hz is 6-8dB down from the output at 20-40Hz. In room, that balance may be further thrown off, yielding less than stellar perceived SQ. EQ can compensate for that to some degree; however, judging by the compression sweeps, the PB12U doesn't have much headroom to back it up from 50Hz on up.