Hi all, just another mercedes audio related post

I have a 2019 C205 (C300d coupe) which after some research turns out has a midline sound system built into it. This kinda puts a spanner in the works as I wanted to add a subwoofer to the boot of the car and run an RCA cable from the headunit to the back. But with the amp being in the back it does make more sense to tap into the speaker cables there.


The problem is that there isn't any diagrams or schematics that tell me which cables are the R and L channels, so I'm hoping someone in the community can point me in the right direction? Or is anyone knows of a way to detect the R +/- and L+/- cables that would be helpful