I've been toying with an idea for a sub. Do to a very strict WAF, I need to fit a subwoofer behind a couch that is pushed up close to a wall. It looks like about 9 inches of space between the couch and wall. I could build a box roughly 9 X 15 X 60... giving about 5 cu ft. One thought is to arrange 8 of the PE 6 1/2 drivers (PE 295-305) in a line array across the 9 X 60 top of the box. Tuned to around 35-40 Hz it doesn't look to bad, not great, but maybe enough for my customer. Looks like I could build this for around $150 w/o amp. The couch and the wall will prevent puting drivers on those sides of the box. The ends will be small (9 X 15). Comments? Thoughts, other suggestions?