Oh ok I get it. So it wouldn't be possible unless there's speaker wires conected both to the stock and aftermarket radio, which would be really complicated.
I guess I'll simply buy a bluetooth ear. Thanks for your answers.
Ok I'm new to this site and english isn't my first language so I'll try my best...
I have installed an aftermaket subwoofer to the factory radio (through the rear speakers with an amp that I believe is connected to the radio) and it cannot reproduce the same frequencies as it did with my...