i highly recommend https://github.com/jaakkopasanen/AutoEq for headsets - though i have not added any of these to pipewire as it seems others have done [i still prefer foobar2000 with APO + Peace + AutoEq]

Nice. Tried with Koss headphones and despite 3 entries (with custom earpads? audiophools are insane) for my model it all sounded the same to my ear when flipping EQ in player. I thought it was broken until I found Advanced and switched Target to Flat - instant difference for the worse :) Same when selecting wrong headphones resulting in bad sound with EQ enabled. Either Im deaf or my super cheap Koss KSC75 dont need additional processing to sound good.

and trying with cd quality audio? from my recollection (using a bose qc 25 in passive mode) from my first setup it changed it a little but i cannot describe it nowadays, i concluded the difference was "better" and kept it for (too?) many years now. funny thing i do remember was adding AutoEQ in twice - once through APO and once through Peace. but i notice it now more when im not listening via my headset, its subtle.

sounds like a win though on the Koss KSC75 regardless though, just makes em more portable to other devices for you