Mr H

I've lost my touch on box building, even with Subwoofer Design Toolbox. It's freaking all confusing now (maybe its the age)... lol. This box for example, how is something like this even calculated? Given how the ports are being shared. As for tuning, is it tuned for 30Hz @ 2.80cuft? I got the specs from http://www.manualslib.com/manual/293713/Mtx-Thunder-T9515-04.html Can anyone get me back into speed?