BMW 1 series 2013
Discussion
The E50 5 series' used a fibre optic system that was a nightmare to upgrade without huge modifications, I believe it was linked with iDrive. Speak to your local audio installer. One near me recommends using an amplifier that takes the input from your factory head unit and modifies the sound from there. If your car happens to use standardized wiring then it's much simpler and will likely end up in a good head unit and some decent speakers.
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