I'm trying to use a TRRS headset with my Macbook Air 2017 (Catalina), but the Air is only recognizing it as output, but ignoring the microphone as input. The headset is HTC-branded (it was included with an HTC smartphone). I did a sound check and the Air isn't picking up sound from the HTC headset mic, nor is "External Microphone" appearing as an input source.
Other relevant facts:
- The HTC headset mic works fine when plugged in to an Android smartphone (not the HTC phone it came with, but a Pixel), and it also works with a Macbook Pro 2019 (Catalina).
- I also have an iPhone TRRS headset whose mic works with the Macbook Air - "External Microphone" appears as an input source. It seems like the Air can tell the difference between the headsets beyond the fact that they are both TRRS.
Is this is a known issue for certain Macbook models? Is there something I can try, to get the Air to recognize the HTC headset mic?
Armed with the info from @tetsujin re: CTIA vs OMTP, I used a multimeter to discover the ground in both headsets. I measured resistance between the tip & second ring, and between the tip & sleeve. Only the tip & second ring registered resistance, so they're both CTIA. There was one difference: the HTC resistance was 18 ohms while the iPhone headset was 36 ohms. I have no idea whether that makes a difference to the Macbook Air.
Also, since the Macbook Pro 2019 recognizes the HTC headset mic, I assume that it has to be CTIA (my brief research leads me to believe that TRRS sockets only accept one standard, not both).
I vaguely recall having the same issue with another Macbook Pro (2016 I think; I don't have this anymore) that didn't recognize the mic unless the headset was an Apple one, even though Android phones could recognize the mic for both headsets. Which leads me to believe older Macs were possibly treating Apple headsets differently, but newer ones don't distinguish any more.
However, none of this gets me any closer to a solution.