The QS series are "quadpolar". They have midrange drivers on the top and bottom baffle wired in phase, and tweeters mounted on the left and right baffles as with dipole speakers. There seems to be some controversy over whether the tweeters are wired in phase or out of phase (and may have changed in the last two years).
In any case, the QS series (QS4 and QS8) are considered to be very good with music, with a nice balance of directionality and ambience. They are fantastic for movies, but admittedly may not be ideal for SACD/DVD-A.
