Perception and Measurement of Headphone Sound Quality
Reply #18 –
All made using professional head and torso simulator equipment costing thousands of dollar, yet the graphs differ. There's simply no consensus on measurement and calibration standards at the moment.
Your links are broken and I disagree. Look at the raw data. Differences at the very low end are due to seal problems (see different raw curves at innerfidelity), difference at high frequencies are due to placement.