I have an M&K 12" sub (older, without any phase adjustment--either knob or switch; it just has frequency and volume gains) with some Dahlquist QX10's on the front. They are powered by a Yamaha 1200 (80wpc). The Yammy has three different setting options for the sub: sub, main, both. When I set it for "sub," it seems (looks) like the mains aren't cranking and I'm not getting anything to the M&K, when I use the "main" the mains totally crank--I'm impressed but afraid by the cone excursion (so far the Dahlquists have handled it with frightening ability, but I wonder what I'm missing without the sub), when I use "both" the mains calm down and sub is engaged, but the bass isn't any bigger than when the mains are getting the whole thing. Help! I'm thinking it is a polarity problem, but I don't know how to (or if I can) change the polarity of the sub.