Headphones

I am going to preface this with the fact I find IEF neutral/harman target upper mode to be shouty for vocals especially. I might be particularly sensitive in the 2-4 Khz region compared to some people. Since a lot of iems target those targets it ends up a lot of the times them not being for me. Which is why I almost always prefer a recess comparitive to the targets there. Now onto why it works for classical for me.

While the bass lacks impact and isn't anything special. It is present enough and detailed in a way that sounds natural. Works for classical music but not as much for say more dynamic Rock music.

The Mids are present, detailed again and rather naturally timbred. The forward upper mids gives more "excitement"/"energy" to a lot of instruments. So along with sounding natural if you aren't too sensitive to it it can make the music more fun. On the not classical music side faster paced Rock, and metal prefers slightly recessed upper mids since that extra energy in the upper mids can make guitars too aggressive and be too much or shouty. Some people do prefer that extra energy and aggressiveness so ultimately it is taste. But I wouldn't use this IEM overall for the more energetic/aggressive genres. Vocals aren't the

What the upper mids does is give a relatively good/smooth transition to the treble. Monarch MK2s treble is good is pretty detailed. It's 5khz is fatiguing to mu ears but your mileage may very on what parts of treble you are sensitive to. It isn't as airy as say the Symphonium Helios treble or as detailed as the U12ts (slightly unfair comparision as U12t is $2k new but can be gotten for $1200 used).

Overall I would say it has a nice timbre to it that works well for classical, live orchestral, acoustic music. But its upper mids, weak bass impact, not amazing but not bad vocals puts it off from working for faster music or vocal focused tracks. But I am sensitive to forward upper mids (and treble in general) so you may not face the same issues.