I did it with a LS 1x12 ext cab to tighten up my other open back cab. It did exactly what I expected tighter, edgier and focused. The two cabs complement each other nicely. I only use the closed back with the open or when recording, by itself it can sound a little boxy, not bad though. I use it with a LSS and use ev sro alnico speakers. I have been playing with a cele. gold in the open back and the sro in the closed, right now this setup kills, what one speaker lacks the other picks up. I used 3/4 birch ply. and used a parts express round jack. I also got some coco tolex off ebay, cheep. I added a thin layer of wool batting to raise the Q of the cab. Its nice to not have butchered up the cab too. and it matches.