'89 LeSabre Speakers

Hey everyone! I just got a crappy '89 LeSabre and after fixing the fuel lines I now have a crackling and popping Right Rear Speaker. I first off exchanged the RearLeft speaker with the Right one and it did the same thing, so it is either my wiring or my stereo, I wiggled both the connectors on the speaker and the stereo while it was on and the crackling/popping was the same. I'm gonna just buy new speakers and run a new wire from my stereo to the trunk, but I need to know what size speaker I have in the back, I know the fronts are 4x6

The rears are 6x9s. If you want something the stock stereo (if it isn't a Bose) can drive, go to meijer and get the scosche factory upgrades ( I have found that these work best).
It could be that the stereo is on it's way out, or has oxidation internally on the bal/fade adjusters (or the equalizers). Spraying a de-oxidizer (the kind used in computer apps, found at a local computer store) in the holes for these will clear it up for much less than buying new speakers.