I'm going to give this a shot. I'm a long Time Lurker, first time posting on here.
I have had the JVC HA-FXT200LTD for about a two weeks now, but before I begin, all this is subject to opinion I stake no claims in being an audiophile I just love to listen to music.
The questions I have seen on this forum so far is mainly how do they compare to the HA-FXT90, since I have both I will try and do my best in telling how I think they compare and differ.
For the base comparisons I listened to them with my fiio x1 no eq. The songs I choose were; Sawano Hiroyuki[nZk]:mizuki - A/Z: mp3 320kbs, Lindsy Stirling - Crystallize: mp3 320kbs, Tchaikovsky - 1812 overt: Flac.
To me the HA-FXT200LTD sound much cleaner, there is a distinctive difference in the clarity.
The Highs
The highs of the HA-FXT200LTD are better while not being sibilant or harsh: I don't think that they are overpowering. They are clearer and cleaner while having more detail.
The HA-FXT90 when listening to the same songs sound, like they do fall behind a bit, the vocals seem a bit lackluster.
The details in the HA-FXT200LTD are loads better than the HA-FXT90, in the 1812 I could her some of orchestra breathing, while I could not with the HA-FXT90. It Freaked me out I thought there was someone in my room breathing behind me.
The Mids
The mids are not as recessed as the HA-FXT90. They are definitely more pronounced.
I read a lot people like to say that the HA-FXT90 is V shaped.
The HA-FXT200LTD I feel like it is more U or maybe W, it has better dynamics to me.
The lows
The lows of the HA-FXT200LTD seem to extend a little better, it rolls off better and extends a bit deeper, however; because there is a bit more bass it can sound muffed at times, although it heavily depends on the song and whether you are EQ'ing it. The bass can be bit overpowering on some songs which I think can cause the song to sound muffed by the bass. A fix to that though is to eq it. With more bass though it does effect pop songs, female vocals sound like the treble has been turned down. Its clear just not as clear as it seems like it should be.
The lows of the HA-FXT90 are just not as good as the HA-FXT200LTD but the benefit to that is if you listen to pop or rock it doesn't sound so treble lacking.
Sound stage
The overall sound of the HA-FXT200LTD is much better than that of the HA-FXT90, it feels good to listen to them I truly enjoy the sound signature of them. I do like to listen to my music with a custom eq setting because I do like a bit more treble, probably because I'm losing my hearing.
Now Don't get me wrong the HA-FXT90 are still great sounding IEM's, is it worth the upgrade? I think so. But I Liked the sound of the HA-FXT90, so when I found that there was a newer model I had to get it. I like both IEM's but i would choose the HA-FXT200LTD because they sound better to me.
P.S. I have been told that I also suck at explaining things, so If you have any questions please ask me.