most of it is the fit issues...
the double stock flange of eterna give me a good isolation but i notice that my left ear sound hollow and unbalance.... i thought at first the earphone broke down or something but actually it was my left ear lobe is bigger than my right.... so i didnt hear quite right...

its all just about the same, try shallow inserting but all i can hear was the bass thumping and i feel so fatigue, so i go for deep insert which my right ears dont have any problem but my left start to sound thin and hollow...  and the sound feels so unbalance....

only ck100 foam tips and custom sleeve that gives me balance to my left and right...
and sounded the bass was more controlled, less harsh on the mids and i can hear vocals clearly