Which frequency to adjust if voices/mids give me a headache.

It’s the amp dirac can not fix it the m10 has a digital a amp that sounds clean yet thin we sell the m10 and that us how it sounds listen to a n aim Ampang you willbe shocked at the difference

Dave AND TROY

Audio intellect nj

nad and naim dealer

@audiotroy the NAD M10 V2 is a PurFi Class D and is not a digital integrated amplifier.  Come on Man you're an NAD Dealer??  

If the irritation seems to be brash or brassy, I agree with the 1.5k to 1.6k give or take 500 Hz. assessment. If the irritation is more shrill, I find more often than not that the offending frequency is around 3.1k. It could also be both regions.

You may want to start with a larger reduction like 6 db or greater just because it is easier to hear bigger changes and then add them back in as needed after you find the offending frequencies.

Treat your room and buy better front end equipment and amplification. Anything else is a band aid.

I've done Dirac room correction and both sets of speakers still bother me a bit.  These are not bright speakers I know.  

@wrecked Since you've done room correction the cause of the irritation may not be brightness. Higher ordered harmonics caused by electronics are perceived as the ear as harshness and brightness, and yes, can be enough so that you might get a headache.

The thing about that is the room can measure perfectly flat while this is going on. Since you already know the speakers aren't bright, if it were me, I'd be looking at the electronics. Solid state amps (in general) are well known for this (which is why tube amps are still around after 7 decades of transistors...). There are solid state electronics that aren't bright due to distortion.

So again if it were me I'd try a different amp and see if you get different results.