12 volts on rear left speaker?

Could someone explane to me why I have 12 volts on my rear left speaker. Everything is unpluged, I am getting this at the plug that goes to the radio. The car is a 97 3000 GT

You either have something wired incorrectly or your vehicle is designed for one of the amp-on-speakers systems, like used in some Bose setups.Support the12volt.com

Ok, I did not think anyone would answer my posting. Here we go. When I bought this car only on speaker would work and that was a front twieater. So I bought a JVC for it. Eliminated the CD changer and factory radio cus checked all speakers with a D type battery and they all worked, also bought the connector that goes from the factory plug to the new radio. Looking at the factory plug someone had replaced the wire for the rear right speaker, after having problems with the car not starting I thoght maybe somethig to do with the radio so I started to look in the wires a second time to see if I did somethig wrong, everything looks good but I have 12V on the rear left speaker and .24V on the front right and .34V on the front left speaker. Why? does this car come with a built in AMP and if so where is it? This is a Mitsubishi 3000GT SL with an Infinity stereo system. Thanks in advance