A lot of the FR graphs you see come from reviewers and enthusiasts who have their own measurement device called a MiniDSP EARS. Not only are these data technically problematic, but what you see is always a massaged presentation made by combining the actual measurements with some unspecified reference for “neutral” called a compensation curve. Without knowing exactly what flavour of neutral is being used, the results are essentially meaningless.
The most useful graphs are done with extremely expensive equipment and provide the raw data in graphical form:
1. InnerFidelity is the gold standard for that, but sadly the guy has retired so no new headphones are being measured there. But for anything older than a year or so, check here:
(-- Ignore the red and blue line curves. These are adjusted via a non-standard compensation curve. The grey curves are the raw measurements.)
2. A very recent source to come online is Oratory:
https://www.reddit.com/r/oratory1990/wiki/index#wiki_full_list.3A
(-- Here the orange curve is the raw data.)
3. Finally, there is Rtings.com at:
https://www.rtings.com/headphones/reviews
(-- Click on any review, then scroll down until you find the raw graph for that headphone. Click on the little graph for a bigger one.)
You don’t ask how to interpret the graphs, so I assume you’re good to go on that. If you had asked I would have referred you to: