From the manual: Page 92 https://images-eu.ssl-images-amazon.com/images/I/D1s3YbL-KQS.pdf
Selects whether to spread the center channel signals to left and right when 2-
channel source is played. If you feel the center sound is too strong, set this
function to “On”. This setting is effective when “
” is selected.
Disables Center Spread.
Enables Center Spread.
Adjusts the center localization (broadening effect) of the front sound field. Adjust
this higher to strengthen the center localization (less broadening effect) or lower to
weaken it (more broadening effect). This setting is effective when “
Neo:6 Music” is
0.3 to 1.0