Something that I've had pretty good success with in the past is a 3:1 ratio bass tube - basically, a tube on the front of the woofer 3 times longer than a tube on the back of the woofer; this can be easily built as an enclosure. For a 6.5" woofer, I would take the size of the woofer, and multiply it by the ratio; so the front tube/path should be about 19.5" long, and the rear tube/path 6.5" long (don't go crazy here - a 21 foot by 7 foot tube won't make it sound better).