I heard about the Beyerdynamic Headphone Lab app from David, on Mixbus Tv, on Youtube. I have a Beyerdynamic DT 770 Pro, 250 OHM headphones, which I bought at a thrift shop(!), for a very low price. I just used the app, today, using the setting that matches my headphones. I may change the settings to see how other headphones would sound, later. It is a clean sound. I need to figure out how to use the other functions of the app.
For non-BD headphone users, it’s perhaps worth mentioning https://autoeq.app/ - a free website which can generate compensating EQ profiles for many different models of headphones, and output presets for several equaliser plugins (as well as generic values).