What size are the factory-fit speakers in the 307?

[pinkneo]

Does anyone know the answer to this? Must have been playing my music too loud because my 307's front pair of speakers now rattle at the slightest hint of any bass! Looking to buy some new (better) ones, but need to know their diameter first, and would rather not pull the inside of the door apart - that kind of thing is best left to the professionals. So if anyone knows - sing out. Thanks!