Official Bavsound how-to video for G30, including all HK speaker locations:
Definitely more of a PITA than the F10, especially the doors:
- extra gaskets are required to feed the speaker wires out to the side;
- the door handle trim is a pig to prise out;
- the newfangled clips round the edge of the door card are prone to breaking and/or not resetting properly. Make sure you have at least a couple of spares per door available before you start.
Replacing the centre speakers isn't technically difficult, but it's ridiculous (of BMW, not Bavsound) that you have to risk scratching up $1000+ of idrive screen and dash trim just to be able to get off the centre grille.
You can also see how the guy struggles to find a point to insert the trim tool under the rear shelf speaker grille. That struggle is real - I gave up after 15 minutes of getting nowhere, but will retry now I've seen the video.