it depends on the symetry of the room. if left and right reflection points are unsymetrical they will effect phase at listening position diferently. any diference in arrival time of given frequencies will shift the center image to the faster side. if the phases match perfectly the center image will be perfect, too
Center can still be better IMO…
-Center anchors the channel to the screen, and is much better for off axis listeners
-You can adjust the center channel level if needed
-For large screens (non AT) where the Left/Right speakers are far apart, the center really does help. A phantom stereo image can sound pretty good but just not as good as a discreet channel with native multi channel content.
Many rooms, like our living room, just doesn’t make sense to have more than 2 speakers and it does sound fine when taking a 5.1 signal and downmixing to stereo. But if I go down into the theater where a dedicated good speaker is used for a center, it just sounds much better IME.
It is interesting how many more 2 channel only people seem to be on ASR. Multi channel movies, tv series, and music can really be quite enjoyable. I find myself spending more and more time in the theater with multi-channel sources and upmixing 2 channel content than in my dedicated 2 channel room these days.