My $.02: I am not a fan of adding a center with L+R info for 2 channels sources unless the L/R setup is suboptimum, such as with too wide spacing.
OTOH, with a real phase/timing-correct and discrete center signal, the overall quality of the entire frontal soundstage is improved. As I have often said, try comparing some of the RCA Living Stereo SACDs by switching between the 2channel DSD track and the 3channel DSD track to hear the difference. Another test is to compare the quality/stability of a mono recording on a 2channel L/R playback to a mono playback only on the center channel and realize that the same thing is happening to the center image on stereo vs. mch recordings.
Also, the reference to the necessity for a center channel predates HT and does not refer to a synthesized L+R center but to a discrete one.
None of these comments directly relate to on-axis vs. off-axis listeners.
Kal
OTOH, with a real phase/timing-correct and discrete center signal, the overall quality of the entire frontal soundstage is improved. As I have often said, try comparing some of the RCA Living Stereo SACDs by switching between the 2channel DSD track and the 3channel DSD track to hear the difference. Another test is to compare the quality/stability of a mono recording on a 2channel L/R playback to a mono playback only on the center channel and realize that the same thing is happening to the center image on stereo vs. mch recordings.
Also, the reference to the necessity for a center channel predates HT and does not refer to a synthesized L+R center but to a discrete one.
None of these comments directly relate to on-axis vs. off-axis listeners.
Kal