Kr4...I beg to differ with you about the effectiveness of deriving a center channel from a 2-channel source. In many recordings where there is a soloist, he/she was originally recorded as a discrete channel, and was subsequently mixed equally into Left and Right. When you derive a center channel what you are doing is unmixing so as to restore what was there originally.
I have used a center speaker for almost forty years, and have used many different techniques to drive it. Some work better than others. Of course, a discrete recorded center channel, SACD or DVDA, is best, but with some recordings the derived method comes close.
