It may have been my old thread possibly..
Glad you have found a solution. The original microphone uses an electret, but with a series HPF (High Pass Filter) in series to boost the upper audio response in the MH3. I found, even using the inbuilt DSP EQ that I couldn’t offset the over-emphasized bass that the audio appeared to have with no high pass filtering in-circuit. The above thread explains what I did to implement the same filter used in the MH3.
I strongly suspect the KX2 is the same. Given that, essentially the circuitry and audio DSP are almost identical in both radio designs..
Jonathan