I'm not sure what the overhead compartment with the mic looks like in the X5 but on the M3 there are two slots in the overhead console. On the left (driver's side), there is the sunroof switch. On the right (passenger's side) there is the mic. This seems counterintuitive to me.
Reading about someone's DIY Bluetooth installation, they just swapped the positions of the sunroof switch and the microphone so that there was better voice quality, and this seemed to do the trick.
I'll be getting mine installed next week and will ask the dealer to do this. If not, I'll do it myself. Let me know if you can do this, have tried it, and how it works. I'll try to dig up the link for you.
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