I can't spend to much on that point, only because I don't know the mind of the speaker....But in my mind that's not what he meant! What I took from it is that you can get a *sense* of a wider stereo effect by reducing the Mid in portion to the sides.....loosely speaking he is right but technically there a better explanation of the effect which you posted.selig wrote: On the second I noted they claimed reducing the mid signal created a wider stereo signal, which of course is impossible because as you reduce the mid you are left with a mono signal with one channel 180° inverted from the other. You totally loose the stereo panning at this point! For example, a high hat panned hard left would now appear in both the left and right speakers with the mid signal removed, which is not at all "wider" as one might expect.
On the demo track I uploaded when M/S was activated on the GQ7 the track felt or sounded wider, by reducing a few Mid freq bands. That's what I think he was getting at!