I have the HK 3485 and it states this right in the owners manual.....
"Speaker 1/2

ress the left side of this button to enable the
HK 3485 to output audio to the speakers connected to the Speaker 1
Outputs,and press the right side of the button to enable the Speaker 2
Outputs.You may enable or disable both sets of speaker outputs simul-
taneously.This feature is a convenient way of hearing audio in more
than one room at a time,although the same source material will be
played through both sets of speakers. "
