wiring a crappy sub

I have an old kenwood cd player with no frills, just front and rear connections and a home theater sub that im not using that beats pretty good for its size, and I'm wondering if theres any way to hook the sub up in my car. I talked to a friend about it and he said the difference in AC and DC power would blow the sub. I dont have any pre-amp outputs on the HU, and the sub just has + and - wires, so how would i wire it? I know I know, i should just spend the money and get real subs if im gonna do it, but i thought i might as well try it for awhile. So, is it possible?