[mrluna]

Hello All, I have a 2015 M3 SGT. A while a go calls over handsfree are practically un-understandable sound is like if it was under water very hard to understand. However music sound is good. I brought it to the dealer and they said CMU was broken and needed to be replaced. Bought a used one on ebay and plugged it, however the issue is still present. I believe I need now to point either to the TAU or the bluetooth contol module. I am not sure where to start as I dont have a clue on what function each of them controls. Anyone has had the same issue? By chance you know if the TAU routes sound differently if music or calls? I noticed on the connection diagram that it has two different inputs. Any insights would be greatly appeciated. Thanks!

2

Hello All, I have a 2015 M3 SGT. A while a go calls over handsfree are practically un-understandable sound is like if it was under water very hard to understand. However music sound is good. I brought it to the dealer and they said CMU was broken and needed to be replaced. Bought a used one on ebay and plugged it, however the issue is still present. I believe I need now to point either to the TAU or the bluetooth contol module. I am not sure where to start as I dont have a clue on what function each of them controls. Anyone has had the same issue? By chance you know if the TAU routes sound differently if music or calls? I noticed on the connection diagram that it has two different inputs. Any insights would be greatly appeciated. Thanks!

Did you get this resolved? If so, how? I am experiencing the same issue. Music and radio are great. All calls sounds muffled/under water.

 

[mrluna]

The issue is actually the Bluetooth profile being used. Here is a short explanation:

HFP is the “Hands Free Profile.” This profile supports only low bit rate, “voice-quality” audio, using the CVSD codec at 8 kHz sample rate or the HSP 1.6 "wideband speech" mSBC codec at 16 kHz*. This profile is used for phone-to-headset communication and for phone-to-car kit hands free communication.

The Mazda CMU doesn’t support the HFP 1.6 wideband speech. What we are left with is something that basically sounds worse than a landline over old telephone wire.

If you use CarPlay or Android Auto, you can use the same microphone to make crystal clear calls (reception dependent).

Note that even the HFP 1.6 wideband codec isn’t amazing, but it’s far better than the original implementation. Ironically the CX-5/CX-9/Mazda6 with the Tom Tom nav touchscreen system (with the blue UI music screens), from around 2012-2015 supported wideband. My Mom had one and I was always really impressed at how clear her voice was over the Bluetooth connection. Now she has a newer Mazda3 and the Bluetooth quality is literally trash.

Hello. Can you help me understand what to do to fix the audio phone call issue? I have Android Auto but wasn't sure from your post if I need to change a setting. My audio on phone calls sounds muffled. Thank you!!