Here are measurements from 3 separate units of Mage Audio modded DT770s taken using the minidsp EARS. The plush earpads of the DT770 make positioning moderately difficult, but these are pretty consistent measurements across multiple units. Having a wide variety of modding resources available to compensate for stock unit variations and channel imbalances helps a lot.
Here is the Right channel of the stock DT770 Pro 80 Ohm for reference:
Black Mage Right channel FR:
MrSpeakers Aeon Closed Right channel FR for reference:
Sennheiser HD650 Right channel FR for reference:
Let me know if you have any questions. I hope this has been helpful and informative!