Well, I flipped polarity on the low split output thats feeds my 15s and it sounded fine. (note the banana plus are in clear vinyl tubing for insulation). If you are talking about a strictly 2 channel system it shouldn't matter - as long as you have inverted polarity between the woofer with reference to the mid driver. But - in my room, its part of a multi-channel system, so I guess I need to go back and correct the woofer polarity, and invert the hi-split signal. Then check to see how it plays with everything else when playing movies in 5.1 mode.
Sounded great with music (2 ch, no subs) and for tonight's movie (Zefferelli's 1968 Romeo and Juliet - basically mono)