I'm happy with using just one B&W ASW825, which has an ultra-rigid. Rohacell® sandwich cone at 12 inches. At one point, I had 2 of them, but ended up deciding to use the second one for my little recording studio and just one for my stereo. It's a non-ported design and sounds nice and tight, much quicker than it's bigger brother, the ASW855, which uses a 15" driver.
bwgroupsupport.com/downloads/specsheets/bw/ASW825%20InfoSheet.pdf
bwgroupsupport.com/downloads/specsheets/bw/ASW825%20InfoSheet.pdf