Well! Out of the box it was dark. Mid bass with very laid back trebles! I was somewhat dissatisfied. But now bass hump is getting flatter and trebles have more sparkle and energy. Initial harshness in upper mids gone. There was little harshness in in the upper middle registers with busy tracks. Now its gone.
Its sound-stage and imaging is phenomenal for an IEM. I heard such sound-stage with Yuin PK1 and OK1 for small earphones. But for an IEM, this is crazy.
Something about its bass! Though it is still bass heavy, it is unique in its bass impact. The bass is clear and has definition. Layered! The heavy bass does not distort the rest of the frequency profile and almost layered around the performance. As burn in goes on; its bass has become more defined and fast. Mid bass hump is less prominent now. It goes really down too. Bella Sonus is a treat to hear. Although bass heavy, it does not give a boomy performance in classical, Jazz or acoustic music. That is unique too. If tracts are bass heavy it gives an insane bass performance. Though I am not a bass-head I really like bass of this tiny guy. My only complain is mid bass hump. It still need more taming there. I hope it it would achieve that with further burning.
Highs have improved and it gives a realistic high frequency response than a coloured treble response. I still like to see little more extension, energy and weight in this region.
I like the coherency of music too. It gives completely integrated detailed performance. It does not give you the idea of a synthetic performance with too much analytical and detailed performance.
If it was more balanced without being little dark, IE8 would have been the king of the IEM world without any doubt.
This is not a complete write up. I am burning it down with stereophile burn-in sequences. I am waiting my new W3 too. I returned my borrowed W3, after a short audition. When it arrives IE8 would be ready for head on clash.