The measurement I took of my (old type) ATH-M50 superimposed on Purrin's plot
Hearing these I could not understand why so many people liked them and thought they sounded pretty 'flat' and accurate as this very old version is nothing like that.
It sounds the way the plot shows.
Humongous (fat) bass with an 'overly warm' signature with the upper mids (clarity) lacking a bit.
The later models have changed quite a bit from the 'old' version.
Earlier I made an attempt to combine plots of different sites to see if they measured similar
the green and thin blue line show a +5dB in the lows compared to other Tyll's plot