We wanted to do something a little different for a recent show, so the evening before we decided to make a box for 3 Critical Mass LS 152 subs. I started it at 6pm on Friday evening, didn't have enough cloth, and used a airline blanket to replace the felt (LOL) and finished it at 5:30pm Saturday for the show that started at 6pm.
It is a sealed box
I got going and forgot to take pics in between the stages, but you will get the point.
They are being powered by a Sundown SAZ 1500d