I'm just starting a box to put my 12" L5's in... tryin to get rid of them.... was gonna go with 1.75 ft^3 tuned to 37 hz... I'm using WinISD for box specs, and it says it'll hit 90 dB, don't know if i can trust this, but seems low for these kicker "spl machines"... any other box suggestions for these things?