SonarWorks Reference 4, a trial. I tried out the trial after Saint recommended it at the start of Ultima.
Essentially it uses a super-sensitive microphone to record the output from the headphones (or speakers if you have to badass version) then calculates the difference between the flat line (red) and the actual output (blue) to set an equalizer and bring the output as close to the flat line as possible (purple).
Unfortunately half of the audio-using apps on my computer have issues with it. When it works, it sounds amazing.
Now I donāt have a studio room and hyper-sensitive microphones, but they are kind enough to have tested a great many headphones in their own studio and provide the averages for those headphones. Those are the graphs I posted.
Thereās also one for the QuietComfort line, but I would have to import it and like I said, itās getting into domestic arguments with my apps every time I start it. But if you want me to, youād have to tell me which ones you have, Hermit.