Lost sound in couple of speakers in 2007 X5

[wwu123]

I was driving our 2007 X5 (E70) the other day when suddenly the stereo sound went somewhat flat and mono. After careful listening to each speaker, it appears the front right and left speakers (the ones mounted in the front doors) both went silent at the same time. The front center speaker in the dash, as well as all the speakers in back, sound fine. We have the standard audio system which I think is the 10-speaker system.

I suspect a wire or connector jiggled loose over time and finally came off. Similar thing happened to the driver door control panel, and I had to pry it open and re-plug in the connecting cable. Can anyone advise where there might be a connecting point where both left and right speakers go through one connector, as it would be unlikely that two separate connectors gave way at the same time? I'd like to minimize the number of trim and door panels I have to take off, so if I can target the highest likelihood failure point, that'd be easiest.