the best one i see in this photo right now is the air pod....

burn in dont exist

but hey atleast im not doing drugs.smoke.alchool.beetle nuts (common in taiwan)

im just interpret freuqency response as like the brightness of a rainbow..the more detail the headphone are the cleaner and higher the resolution of a rainbows are

let say for example...a v shaped headphone it brighter on both end of the spectrum but that doesnt mean the quality of both end are better..it just that contrast is more towards both end then a neutral one

fr can correlate to technicality but it never is the full picture

if it a health issues

GO SEE A DOCTOR NOW GO GO GO GO GO GO

no seriously the longer you left it untreated the worse it gonna get

technicality exist but mostly we cant measure them and it subjective because it kinda differs between ear to ear

but stuff attack and decay exist and we can measure that by using impulse measurment or square wave measurement

however the rest is mostly material and aerodynamic science stuff