Another design data point that has me inquiring. The 1st port resonance at the above spec'd enclosure and tuning is around 218 Hz. I plan on crossing the subwoofer over at 300-350 Hz and if I'm not mistaken a general rule of thumb is having the 1st port resonance pushed at least 1 octave above the crossover frequency which would never happen in this case. Makes me think I'm back to the drawing board a little bit for design. This sub would have to use the passive radiators or be sealed.