Port Volume Included in Total Volume?
 

I think I may have screwed up my subwoofer enclosure...

Its 17.5" cubed. .75" MDF. When I punch that into the Rockford Fosgate subwoofer box wizard it says the internal volume is 2.37cu.ft. Now, for arguments sake, lets say I had a port inside that box that was 2x10x20, or 400cu.in (.231cu.ft). Is that volume subtracted from the total volume of the enclosure, or is only the displacement of the MDF used to build the port subtracted?

you need to add everything that will displace the volume that you need for the proper tuning of your enclosure. So if you needed 2.37 ft3 just for the volume of the box you would need to add the .231 ft3 for the port (not just the MDF) to the total giving you 2.6 ft3 INSIDE the box. And dont forget the woofer displacement too.