Opened mine because the voice mic was not working properly. The mic was almost muted, it did just let some scrambled peaks through.
After replacing the voice mic, things got better but the sound of my QC 35 II is still far worse than in this review, check from minute 2:35.
Even in a quiet environment my speech is almost not understandable.
So Bose put some effort in using two decent mics for noise cancellation but two cheap MEMS mics for speech, one for monitoring
environmental noise, one for picking up the voice. I assume, if both are mismatched, the sound of speech gets degraded.
I made some test calls and covered the "monitoring" MEMS with my finger, my voice got a tad clearer - but just a tad.
Switching ANC On-Off has no effect.
Any Idea how to improve this? Because there is no need in buying a new headphone...
In the pictures:
-Speech-Mic-Main-PCB:
The main PCB with DAC etc. with the ANC-mic on the left and MEMS on the right (U500)
On the back (not visible) is a 30-pin connector to the
Speech-Mic-Connecting-PCB.
-
Speech-Mic-Connecting-PCB
The connecting Board between MEMS Mic, the NFC board and also the drivers.
It connects to the main pcb with a 30-pin connector (on the back, not visible).
FM+ / FM- / FMB on the left are the connections to the MEMS-mic.
Only FM- has a direct connection to GND. No other "direct" connections to the "solder-blobs" on the right.
(I used the short circuitry function of my voltmeter.)
I wonder if FM+ / FM- are connections to the MEMS and also to FB+ / FB- on the Main PCB
FB+ / FB- are close to a recess rather in the middle of the picture.
-
Speech-Mic:
The MEMS for picking up voice. The marking reads MU20 6A04.
-Wiring:
Just to show that I replaced the connecting PCB ( it has some resistors and capacitors on the back)
together with the mic for speech.
And yes, the wires can very easily be mixed up. No Idea how they manage this in the factory.
-Assembled:
The main pcb back in place. Re-soldered like it was before.
On the left you can see U500, the monitoring MEMS - mic.
Do you see the the white and black wires connected to FB+ / FB- ?
To me, black would normally be the color for - (Negative)
But I checked a video where a QC 35 II is disassembled and the wiring is correct , white negative, black positive
Any clues how speech could be improved? As the MEMS for speech is on it's own passive pcb,
can it be replaced? Maybe with a condenser mic?
All the best, Herbert