91 SE front speakers intermittent

Although my rear speakers are loud and clear, I seem to get sound out of the front left and front right door speakers just from time to time. I imagine if these speakers were blown outright they would never be active, so I figure its a wiring issue. Its an older car, so wear is expected. Any thoughts on where I should begin looking for wire fraying?

try at the speaker and the connector behind the head unit. if both places looks fine...only place left is somewhere between those two spots. in that case...its probably faster and easier to just run new wires to the speakers than trying to find the short.