IMHO, it's popularity comes from the concentric 12" driver. I have Emerald Physics 3.4s, floorstanders, OPEN BAFFLE, OUTBOARD XOs, 12" CONCENTRIC DRIVER WITH 1" POLYESTER TWEETER. Sadly, they are no longer in production, BUT, they come up FS occasionally at a fraction of the MSRP of these. The 2+ series additionally has 15" woofer/s