http://www.adireaudio.com/tech_papers/spl.htm Try your subwoofers using their formulas. I was deeply surprised. One of the subs I was considering claims 88 dB SPL. It came out as really having 83 dB SPL. Other one claimed 90 dB. Came out as 89.5 dB SPL (nice!). And the last one I tested claimed an astounding 96 dB SPL. Guess what. It pumps out 88 dB SPL! Interesting read. I wonder what your opinions are about it. Javier.