this headphone go now cheap around 25 eur. there is since some time a 681 EVO out. it cost ~ 30 eur. have somebody measure the new version so can compare with the old ?. there is from the headphone simulation program morphit from tone booster a profil for this. on their page they show the 681 and the 681 EVO.
here is report 681 that it have less bass, morphit too boost much bass for 681 but the EVo seem have more bass and it reduce bass. the screenshot are correction curve. i currently have a sony zxr 310(support on morphit). this is on ear and have very few stereo width. thats smaller as the JBL 104 BTW. I have a panasonic RP HT 030 have much more stereo width but is not support in morphi(i report 1 year ago to add) . So i can not simulate the Stax good .
I hear a stax in real life, I like the sound, and this have much stereo width even if the stax sound reduce alot of 2.5 khz. so my sony can not do it.
I notice that every headphone produce more bass, when more mechanical pressure from headphone is on head. so my question is too. have the evo version more preasure on head as the old version ?. i like a headphone that have fewest pressure ear. if bass is weak i can correct
https://www.toneboosters.com/tb_morphit_v1.html