Maybe this is like the Sony SA-WX700 "push-pull" sub? I think they're no longer made. They were inexpensive, and I bought one. Mine broke (as did many of them, I gather) after a year or so. I still have it sitting in a corner of my listening room, waiting for me to replace a condenser, in hopes that would bring it to life. I was pleased with it, while it worked, but I couldn't give you a good critique.
What I'm talking about is not push-pull. That Sony resembles an isobaric design. In a dual opposed the drivers would be push-push.
I'm seriously considering buying a pair of inexpensive (aka cheap) drivers and building a very basic enclosure just to see what gotchas I might come across.