It's the one in the side panel below the right rear window. I can post a picture if it will help. I poked around with it for a little while, but couldn't see how to get it out to determine the problem is with the speaker or the wiring. Any done this before? Thanks.
Check out the "Garage shop Manual" at Clarks Garage. He has a very detailed DIY on the process. It looks like there are two ways to go about it. I haven't had a chance to do this myself yet but it looks like it will be some work.
Clark's Garage
Thanks, Josho - it took me a few minutes of maneuvering though Clark's Garage's web site, but I found the right link, which led me to the instructions. Doesn't look like a fun job, but not insurmountable, either. I'll tackle it soon; I'm tired of hearing sound only out of one of the rear speakers.
Note that the 968 has a different rear window than the 944. The 944 is held in by the seal and the 968 is flush mounted.