kick panel= 5.25"
door= 1" tweeter
door= 3.5" (not in all models)
rear deck= 4"
rear deck= 1" tweeter (HK option)
The number of speakers depends on which audio trim the car came with. The premium has 8, and the HK system has 10. The 318i/is/ti versions came with only 6 speakers unless a higher package was selected, while most 325/328s basically had the premium as standard, as I have yet to see one without the 3.5" in the door.