1997 C280 w/Bose
 

Hello. Can someone tell me why the rear speakers in my C280 are somewhat different. Looks like one has two speakers and one has one speaker in it? Thanks so much!

Same here...
 

I have a '97 C230 w/o bose, but the speakers are the same configuration in the rear. I've always wondered why there are three. If I remember correctly though, the numbers on the back of the speakers are the same for two, but different for one of them, suggesting it's a different type of speaker. My guess is the extra speaker is specifically for bass?
But, I figure the hole for a fourth speaker would be a great bass port should I decide to buy subs.

There are 2 stereo speakers on the rear deck... one on each side. The third, driver's side rear deck speaker is for the optional (prewired) Speakerphone speaker.