Circuit/System Description
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The radio head unit provides four discrete channels to the speakers. Each channel consists of two wires that connect to a speaker. During normal operation, the radio applies approximately 5-6 volts to the plus (+) and minus (-) terminals at the speaker. The terminals attach to the speaker voice coil.
In order for the speaker to produce sound, the amplifier in the radio will raise the voltage on one terminal and lower the voltage on the opposite terminal, then quickly reverse the polarity. The constant switching of the electrical signal causes the voice coil and speaker cone to move rapidly in two directions. The movement of the speaker cone produces sound.