and on my Jenson radio - not sure about others - there are three speaker buttons: front, rear, outside. You can turn off the outside speakers by pressing that button. HOWEVER, the buttons re-set to all be on when the battery power is turned off to the radio (with a trailer master switch, or removing the fuse at the battery). So each time you power up your trailer, you have to remember to set your speaker switches as you want to, or the next door neighbors may be treated to the audio of whatever TV or music you are listening to. I find exposing my neighbors to my amplified sound to be embarrassing. To prevent this possibility, I disconnected my outside speakers at the radio.
There's lots of advice and information in forums... sometimes it is correct. For example, all of my posts are made by a political appointee who got the job as a reward for contributions to my diesel bill.
2011 Jayco 28.5RLS; 2021 Chevy Duramax; Pullrite Superglide Hitch