Rene,
Quote:
what if there are less speakers than chanels? In particular, what if there is no center channel speaker?
If there is no centre speaker, then the centre channel content is split evenly between the front left & right channels. This is done automatically as a function of setting the speaker configuration, so there's no need to manually control centre channel steering.

BTW, what do you mean by digital and analogue matrix modes? All the matrix decoding and surround processing in the 990 is done digitally. PLII, PLIIx, Neo:6, etc, have always been implimented in the digitial domain (not analogue) from the very begining when they were introduced.
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Sanjay