well i did replace them with some Hertz tweeters and i even tested the originals too once they were disassembled and they seem to work

ye there were original volvo speakers there.
maybe only the ones with a seperate amp has the back tweeters cause on this one the tweeters are there (16/57 & 16/58)

well i have some problem with that i get no sound out of the tweeters in the trunk. I thought before that it was the speakers but now that I put some new one in it still does not work. the speakers in the rear doors work, I don't really know if the tweeters go from the same cable as they to the back...