I'm putting together a wee setup for my mother and I'm using old speaker cable I was given by a friend. The cable I have for my setup has a clearly marked + and - on the cable, but these cables don't. It has a row of arrows pointing up the the length of one side, and some rectangular blocks running up the other. Could it be that the "blocks" are negative cable, and the arrows the positive? Sorry if this seems overly obvious.