I built some in a crude way decades ago, but more recently wanted to modify an enclosure to hold subwoofers. Dunlavy recommended joining the DIY Loudspeakers list, and I did, and got a discount on the subs I bought and a lot of good advice. You'll be buried in email, but you can delete most of it. I don't have the Web address, but you could do a search and find it. If you can't find it, get back to me and I'll try to find it in my chaotic records. There are a lot of RFEALLY knowledgeable people writing for the list, as well as the usual assortment of flakes (as far as I can tell). Good luck!
