Me and a friend are about to acquire an Adire Tumult and really need to figure out a solid design for a ported enclosure. We're thinking of a tune somewhere between 20 and 30 hz...I realize that 20 hz would entail a huge portlenght. I don't have the PR option as after the tumult money will be scarce. I would also like to keep the volume to not much more that 4 cubic feet. Any Ideas...I'm looking for something around the Q.707 department.