Thats a particular divvy bit of prat that afflicts otherwise brilliant early models of the Stereo Dimensional Array speakers from Polk. An interconnect cable conjoins the two speakers carrying out of phase versions of each amplifier channel to the opposite channel's speaker. That signal is passed to one side of the SDA array, maths and physics happens, and each channel's crosstalk is nullified before it can reach the opposite ear. Quite nifty, actually. Bob Carver, the genius, did it with electronics so you can have a similar effect in most any good system without towers that are near two yard