Nickbuol
I have one of those SVS 20-39s, awesome sub. 8-M3s! Great speaker. What DIY sub did you put together?
I basically built a SVS 20-39 Pci clone, minus the cylinder.
I had an extra amp that I got from SVS when I was having some really odd issue where my SVS would randomly (after about 6 months of ownership and being connected to the same gear and electrical outlet) go to what seemed like max volume and a super deep note. I tried plugging it in elsewhere in the house and it would still do it. Even disconnected from everything but power it would still come out of standby mode and do it. They sent a new amp, didn't want the old one back... New amp did the same thing. I then just out of dumb luck bought a small single outlet surge protector... Problem went away. Now I had a spare amp.
Bought a Dayton Audio 12" Reference HF woofer (can't recall the exact model, but it is the one that a lot of people use with great success) as my closest option to duplicate the woofer in the SVS. Built the cabinet with the same internal cubic feet, found images online to guestimate the amount of foam fill material. Used the same size port, and configured it "port up, woofer down" like the SVS.
The only significant difference, besides being a lot heavier, is that there is no built in wood "plate" under the feet, so it technically fires straight down into carpet. I've toyed with getting a simple 1/8" piece of MDF and putting that under the sub, but others have told me that it really won't make much difference as the carpet isn't really stopping the woofer from performing well.
So it is a beast. If I ever sold by SVS and my "audio clone" of it, I would build probably dual 15" or maybe even 18" front firing subs. Maybe not ported either just for more of that "thump in your chest" feel. The dual sub setup with ported 12" gets nice and deep and does great with explosions or "muscle car rumbles" but I think that I would almost rather have the sharp attack of a sealed sub.
