Hi all. This is my first post on this thread. I'm less experienced in audio than most members of this forum. I see references to phase coherency of multi-driver IEMs, and whether they are coherent or incoherent. To my knowledge this has something to do with what time the signals arrive from each driver -- but I'm probably butchering that explanation. A number of reviewers have mentioned that the ZS10 has coherency issues. I have noticed that the ZS10 sounds muddled during fast phases of music, with a lot of different instruments and sounds at play. It seems like instrument separation goes out the window and everything muddles together into one noise. It's not bad outside of those cases. On the other hand, my ES4 doesn't do this. Is this phenomenon that which people refer to as a coherency issue? And is it the result of poor crossovers?