Audio consumer, modding hobbyist and vintage headphone enthusiast.
I have owned collectively over 300 various headphones, headsets, IEMs and earbuds.
All measurements are made using a miniDSP E.A.R.S. binaural microphone jig: https://www.minidsp.com/products/acoustic-measurement/ears-headphone-jig
Fundamentally it is a binaural microphone/headphone stand with simulated silicone ear-lobe mounts.
It is the most simple all-in-one measuring tool available.
Cheap all-in-one solution
Not the highest quality materials and parts
Works well with free REW software
Silicone ears are too stiff resulting in poor seal of on-ear headphones. Human ears are more flexible.
Height adjustable headband mount
Silicone ears have 4 protruding screw-heads resulting in poor seal of over-ear headphones
USB - plug and play microphone functionality
No angle adjustment of the ears which can lead to a poor seal
Consistent results for large over-ear headphones
No simulated ear-canal
Inconsistent dip in graphs at 4KHz. Most prominent with closed-back headphones.
Some headphones require rubber bands around to apply more pressure to create a seal
No width adjustment. It is a very narrow head-size, like a child's head.
All headphones were plugged into the same source - audio-gd NFB11.28 TCXO: http://www.audio-gd.com/Pro/Headphoneamp/NFN1128/NFB1128EN.htm
Most measurements were made in High-Gain mode.
Some vintage headphones and sensitive IEMs and earbuds were measured on Low-Gain to avoid any potential damage to the drivers.
All graphs are made using REW: https://www.roomeqwizard.com/
All my graphs use the same scale.
All my headphone graphs use the 'Headphone Calibration' compensation files provided by miniDSP unique to my E.A.R.S. jig. All IEM and earbud graphs use the 'IEM Calibration' file.
The frequency response scale goes from 10-20,000Hz. I do this for 3 reasons.
Firstly, to make these graphs somewhat comparable to other measurements online created by other miniDSP E.A.R.S. owners/users.
Secondly, to make these graphs somewhat comparable to Tyll's graphs on innerfidelity.
Thirdly, there are too many online graphs that start at 20Hz. There is so much information and character of a headphone you can learn from seeing the lowest sub-bass performance of a headphone. Headphones that have a strong sub-bass down to 10Hz more often present music with grander 'scale' and dynamics. There are many headphones that start rolling-off strongly before 20Hz which is often why there is little regard given to these frequencies, but my experiences with hundreds of headphones taught me how important it really is.
While the dB scale remains the same for all graphs, the relative position or 'height' of one graph to another should not be taken as meaning anything, and as such should be largely ignored.
IEM and Earbud graphs are largely inaccurate because the miniDSP E.A.R.S. jig is simply not designed to measure these properly. I have tried to measure them as accurately as possible using as consistent a method as I can, however none of them should be taken with much authority.