Ha, ha, ha.
Disco, don't believe fungusman. Electricity doesn't flow through a thicker wire quicker.
And ozzyo99 has got it backwards. A thicker guage wire doesn't increase resistance. It decreases it.
Reduced wire thickness increases resistance. And more resistance in the wire decreases the volume that comes out of that speaker. So you'll get less volume out of the speaker on the side where the wire is thinner. But it'd have to be a lot thinner to make enough difference to be noticeable in a car.