Hey Rick, when I did my dual center tests with the M22s I tried them in just about every conceivable configuration. The only time noticed any cancellation was when they were laying horizontally with the tops (tweeter ends) very close to each other. At one distance the SPL difference on either side of my head was so great it was almost nauseating, actually worse than having only one side of a headphone playing.

Otherwise the general impression I got was that dual centers in certain configurations created a neat “wall of sound” effect that was cool for movies and poor music recordings. However, for good music recordings with discrete instrument and vocalist placement it muddied the soundstage.

Dean

3M80 2M22 6QS8 2M2 1EP500 Sony BDP-S590 Panny-7000 Onkyo-3007 Carada-134 Xbox Buttkicker AS-EQ1