I think it might be better to figure these as sealed enclosures and just make some slightly different boxes for any ported design you guys might want. I do think a couple of these could be used for a ported box with no problem though.
Keep in mind, the following picture does not show the front baffle that covers up all the seams.
The smallest sealed box is 14" x 15" x 16" deep with a double thick baffle. It nets around 1.25 cu ft. I figure it could be used for most 10's and some 12's. Bracing does go along the rear panel, but it can easily be cut out for plate amp installation.
Next up is a sealed box 16" wide x 19" tall x 18" deep with a double baffle. Notice an extra horizontal brace. Net volume is around 2.25 cu ft. Good size for many sealed 12's, some ported 10's? This is plate amp installation friendly.
Stepping up to the bigger boxes. 18" wide x 23" tall x 20" deep with a double baffle. This size gets 2 vertical and 2 horizontal braces. Not volume comes in around 3.5 cu ft which should be great for sealed 15's and some ported 12's. Again, installing a plate amp will be easy.
The box for the 18" was going to be 22" wide, and it still can be. But I went ahead and had them make it 23" wide x 23" tall x 20" deep and of course with a double baffle. There's an optional brace that can be used to tie in the front portion of the box even more than the previous photo showed. This box is not as plate amplifier friendly because I figured most people would be using pro amps. I can always get them to change one of the shelf braces to allow for an easier plate amp to be installed if needed. Anyway, this box nets a very nice 4.5 cu ft. If we decide on 22" wide, that would drop to a little more than 4.25 cu ft after we subtract off bracing volume.
If anyone can think of a different size or shape that might make sense, please let me know. I'm not the best at modeling subwoofers so if anyone would like to see a ported design for a specific driver, I'll do my best to get things rolling.
If anyone would like to make suggestions on some very common models that should have a specific enclosure......sealed or ported......I'll see what I can do.