FWIW, going by PSA's output comparison, in 12Hz tune, the FV15HP is at parity with the XV30f in the 20-32Hz, and falls behind by ~2.5dB from 40Hz-63Hz. Of course, if we use the numbers for the FV15HP's native tune (18Hz), you'll get average figures of 122.5dB from 20Hz-32Hz (1.5dB better than the XV30), and 128.1dB from 40Hz-63Hz (a deficit of 1.2dB), both reported at 1m peak and converting to Pascals for averaging. Not too shabby in my book considering on the face of it you're looking at a sub with a single 15" driver versus another boasting twins.