Hello everyone!
I just made this bass tube as an experiment and the results are amazing. It hits so hard the gain on the 60 watt amp is only at 30%. It was relatively easy to make. Just use your sub's volume requirements and follow the general shape you see in the pics. For example, my sub requires 1.0 cubic foot of volume with a 7.7 inch long 3 inch diameter port. The sub's frame and port volume are already factored in. Using simple math it was easy to figure how long to cut the 10" diamater tube. 1 cubic foot equals 1,728 cubic inches (12x12x12). 3.14159 (pi) times the radius of the tube squared (25) gives you the area of the tube's diamater in square inches (78.539). 1,728 cubic inches divided by the area (78.539) equals how long the tube should be. (22.01 inches)
I used pieces of an old entertainment center I dis-assembled to cut out the sides. For the port I used a cardboard tube from some pallet shrink wrap. You can use PVC if you don't have a cardboard tube. For braces I simply cut out four for each side from the scrap left over from cutting the sides. Mark everything carefully and test fit then glue in place. The liquid nails sets up pretty quickly so you won't have time to cut anything while glueing. Make sure everything is laid out before you begin. I did not use any nails or screws to assemble the tube. It is all glued. Make sure you set the braces in the glue and give it a few hours to get hard. Mine is rock solid and shows no signs of cracking. The only screws are the ones holding the sub. You WILL need a piece of fiberglass insulation minus the paper backing to stuff inside the tube. Don't fill it up. Just a piece folded in half close to the port tube will do the job. Keep in mind it will not hit as hard if you don't have the hatch glass closed. Even with my inside hatch compartment door closed it still hits very hard. I would imagine you could paint it with just about anything you wanted to finish it. The bass is tremendous.