Stop in for a cup of coffee

I have bought a brand new speaker for my 1965 Dart, and it has these flat contacts for the power. One is the regular size that is used for many things in a car, while the other is very narrow. Which one is plus and which one is minus? There is no information about that in the box with the speaker. I assume maybe all speakers are like this. I would maybe assume the wide one is ground or minus.

Bill