No Sound in rear door speakers

[unhguy86]

Hi all, this is my first post as I just purchased a 2000 Disco2 over the weekend. Everything seems good so far, but I purchased it knowing that the rear door speakers were not working. This included both HK tweeter and woofer speakers on both the passenger side and driver side rear doors. The sub in the tailgate work fine and all speakers up front check out.

Does anyone know the best way to start troubleshooting this?

Thanks,
Chris