WalledSonic

Designed my ported box in TermLab.  Calculation and measurement while I built the box is telling me I'm tuned to 33Hz.  Used an IM-SG to confirm box tuning is actually 26Hz.  Perceptively, I thought 33Hz really was the tuning frequency, but I was mistaking it for the onset of cabin gain (Starting around 32Hz and dropping around 48Hz).  

Lesson learned: calculations are approximations, and tuning frequency of a box is hard to discern by ear once its in the car.  Max port velocity and minimum excursion is what I should have been paying more attention to.