Some words about Nicehck ME80:
1) Soundstage is meh, kinda gets to sides of your ears, but feels forced, like if sound was just pushed from the center to the sides of your head. nearly all my IEMs have better (can't say bigger - IEMs will always sound like something inside your head without an exquisite amount of dsp's and equalizing) stage. Examples: KZ ZS6, MDR EX800ST, HIFIBOY OS V3.
2) Awful treble and mid peaks.
3) No bass below 50hZ, pressing them against the ear reveals boomy, trash low-frequencies.
4) Resolution in treble is... there?. Yeah, it doesn't really help.
5) Good build quality, they do look good.
I can describe their sound as cheap. They do provide sound, that is all.
A pair of 8$ Sennheiser MX170's sounds a lot better. Please don't buy them, as they still sound like cheap earbuds, I'm pretty sure you have something better in your collection.
About burn-in - it never happened to any of my dynamic IEM's. They may change the sound for me, but that's purely psychological, my sound perception changes several times throughout the day, which clearly shows when I'm listening to KZ ZS6 or MDR EX800ST.
Wasted 10$, bought them just for fun, and they didn't disappoint - they are just as bad as I thought. Same goes to **** PT15, only thing is: I expected a lot more from them after reading some reviews.
Good things won't be sold as cat-in-the-bag.