Sub usefulness in constrained placement situation

I used an HSU VTF-2 in the configuration you're describing, behind the couch, but with less space between it and the back wall than you're describing. It worked extremely well in my space. Give it a try. The sub fit perfectly underneath a very narrow, long table that was just the height of the back of the couch. I can't use that setup where I now live but I preferred it to my current configuration.

Thanks - I really appreciate the help and real world examples !! The end table idea is another option as well, though the WAF threshold will be higher there.....Thanks again.

I bought a DD-12 because of the need to control a difficult room, and because I only had a couple of locations to place the sub. My main speakers are Thiel 3.6's (as I said, major room difficulties, or else I would not need a sub) driven by Theta Digital Enterprise monoblocks. At first, I was skeptical as to how the DD-12 would fare in such company, but I have to say it showed its mettle in spades! Truly a fantastic product! Not only does it provide you with a great level of control over numerous variable, but it is just inherently a dang fine sub.

Accordingly, I would strongly recommend the DD series for your application.

Tom.