Why are the left and right discrete rear channels phase shifted by +/- 45 degrees?
To ensure non-EX sounds (effects intended to only be reproduced by either the left or right rear speaker(s)) the l/r surround channels are encoded with a phase shift of +/- 45 degrees. This limits l/r surround information collapsing to the rear surround (which would create a rear mono-blob type effect), and also keeps the sound from being pulled to the Extra channel (which is phase shifted by +/- 90 degrees.) I would propose Dolby included the phase shift to offset the limitations of Dolby Pro-Logic which detects signal dominance to adjust output gain levels. I dont foresee any apparent negative effects from the surround channels being phase shifted as this occurs in Pro-Logic and in a way with THXs decorrelation effect.
