This unit is equipped with two sets of speaker terminals (SPEAKER SYSTEMS A and B). One set of speakers can be connected to each set of terminals, and a total of two sets of speakers can be connected.
The same signal is output from the SPEAKER SYSTEMS A and B terminals.
When only one set of speakers is to be connected, use either the SPEAKER SYSTEMS A or B terminals.
You can use the SPEAKERS A and SPEAKERS B buttons on this unit to set which speaker terminals are to be used to output audio. Set according to the speakers connected to this unit. link