If you want to increase high frequencies on a mic, reduce bass frequencies

At your own risk.


Possibly the best way is an inductor in parallel with the mic's output, A Pleiades filter.


Or an inductor in series with a resistor and the total in parallel with the output of the mic.


Good dynamic moving coil and ribbon microphones will reveal great treble as the resonat frequency of their membrane, diaphragm or ribbon is not at high frequencies.