rofl i tried it and this is what it told me
Given the input, SPL: 138.16 +/- 2dB
Upgrade to more power, also check out ebay for some funky pups, big output gain.
spl may be close though lol im running one memphis m3 of a mtx jh1200 in my tahoe so it may be around that but deffinitley not a reliable way to determine spl