Sonos Amp and Port may optionally output mono instead of stereo. Dual Mono is ideal when speaker placement is not suitable for stereo listening (e.g. open spaces or outdoor configurations). When in this mode, a mono signal is sent to all speakers regardless of connection to an L or R terminal.
On iOS or Android:
Open the Sonos app.
From the Settings tab, press System.
Select the room where Amp or Port is located.
Press Stereo/Mono.
Press Dual Mono.
