Generic ported box for a 12 inch subwoofer.
Box will be 33 inches wide, 15 inches deep, 16 inches tall. 
Box is 2.55 cubic feet before sub displacment. 
Mounting depth of 10.25 in.
Tuning frequency after typical displacment is 33hz 

This is a word document with all the information you need to build this subwoofer box, including pictures.