bromo

yes sir. impedance rise is highest around box tuning (for ported boxes of course) No, in a ported enclosure you will have two impedance peaks and the tuning frequency is in between them. Like this one would be tuned to ~31hz.

Your sketch up design is made with .5" panels, while your calculator is .75". Also with a design like that I would calculate each side as its own slot port box using 3 of the box panels.

http://vault.alpine-usa.com/products/documents/OM_SWR-1222D.PDF

For a sealed box I'd pick right in the middle of it at 2.3ft^3, then you can experiment for yourself and throw blocks of wood in there to take up space or polyfill to make the sub think it has more space. Find a combination that you like then keep it that way.

whoops must have misread the dimensions. So its 6.05ft^3 after displacements the tuning is going to be higher then the calculator says because of the volume difference. It will also be higher with the 45 in the port shortening the port length.

Internal volume is wrong which means the tuning wont be that either. internal width of 33.25" * internal depth 22.5" * internal height of 14.5" = 10847.8125in^3 / 1728 = 6.28 - .42 sub displacement = 5.86 ft^3