Because the wiring on the stock systems is all set up with wiring harneses, which wires on the head unit are the left and right speaker wires. I ask this because i am in the process of wiring an amp and sub to the factory system. i have everything figured out except i have this Line out converter so i can have RCA preouts for easier instalation. I need to hook up a couple wires to the left and right speaker wires, and i dont know which wires are speakers wires. any and all help is apreciated. Thanx.