All the cubic feet numbers given in the supplied charts include the displacement of the woofer. Should this be doubled when putting 2 in one box? Make sure the construction of the box is solid and stable before building the rest of the box. These plans to build a subwoofer box are simple and are only meant to be used as an example for your own subwoofer enclosure. For the ported boxes, the displacement of the port … Per the informaton listed on the Crutchfield website the ideal box volume for this sub is .5 cubic feet. Each subwoofer is different and you will need to design a plan for your subwoofer enclosure. Yes, you can design a subwoofer box for deep bass by calculating the least depth of the subwoofer box, minimum height, and width of the subwoofer, determine the internal dimension, and volume required. Box Building Hints; Conversion Chart; Box Building Hints. All of these plans for subwoofer enclosures are based on a JL Audio 10W1 subwoofer. Spray adhesive onto all sides of the box… Step 3 – Cover and fill the subwoofer box. Cut a large piece of black felt, enough to cover the entire box. Plans to Build a Subwoofer Box. You should first make a sketch of the subwoofer box … I want to build a sub box for 2 JBL Stage 810's. I have built a 10" single sub box …