So I listened to S-EM6 today. I also took time to run some measurements on it as well I don't know but it seemed that the unit I had was somehow faulty.
Anyways... S-EM6's sound is a continuation of the Ear Sonics' sound signature. It has all the best futures of SM3 v2 and SM64 combined. What really impressed me was bass, which is really "big" but in a good way it goes really really low and has that fine deep texture. Next thing was soundstage - simply wow - one of the best from Universal IEMs. It has spaciousness and airness of a regular custom IEM. And the resolution - also wow - there are layers and layers of sound. Very impressive.
Highs remind a lot of SM64 - they can sound a bit harsh but overall are quite extended and detailed. Mids are typical for Ear Sonics - close, slightly intimate and a bit thick on the low note and bright and light on higher notes.
These are almost all very positive impressions.
What was possibly 'faulty' about the unit you had? Was it something that was revealed by measurements as opposed to listening or did it correspond with the not-as-perfect highs?