I really have a lot to say since I put ATH-E50 in my ears.
I don't think that I'm capable of making an in depth review but really want to say something about E50 which has fallen behind E40 and E70 review/comparison folk.
After the treble-monster CK10, and for a short time using of V-shaped AKG comes with Samsung Note 8, E50 can exactly be named as mid-centric iem. This was my first expression when I put these in my ear first and it was a bit 'disappointing'. Still when I put them after a while and press 'play', I feel the same, I will explain why I feel this way. Though this is not ALL of course.
I listen almost every kind of music, mostly trance, jazz and classical. I also like listening pop and acoustic from time to time, and I've tried with almost every genre so I think this would reflect what the characteristic of E50 is - at least for me.
Bass: I've spent 10 years with ATH-CK10 and it was a dual BA iem. E50 is half - single armature, but double the amount of bass! I'm not a bass-head, but really started to wish some more bass than CK10 had as years have passed. But I'm also not fan of uncontrollably bloating bass as some V-shaped dynamic iems have. I can easily say that CK10's bass response was very quick and right, now E50 does the same without losing control and mid-bass 'hump. Beside these, maybe it's not stretching, but a tad punchy when it's given in such way. Really fine. It is mostly enough for anyone who is not a bass-head like me but in some cases you wish you had some more maybe(?). But be sure, wishing more makes you an enthusiast of 'fun iem', so this one is not for you I think.
Mids: As I said above, for the first impression when you come out from another characteristic iem, it makes you feel like 'these mids are really forward'. But as you listen for minutes/hours I think your ears get used to its style and start not to think in this way. Yes, still it's a tad warm, especially when I compare it to analytic and cold mids of CK10 accompanied with airy trebles. But it is really really close to natural and very much detailed. Hence, my disappointment leaves its place to a listening joy. You can easily hear/recognise finger moves on guitar strings and piano, also excellent vocal details in every aspect. Splashes, coming closer or taking her/his head away from mic, stress on words etc. Sooo nice and also so hard to imagine how E70 would be much better on this. Even if I haven't listened to it, I can understand why they call it as a studio monitor king at that price level.
Treble: Not as much as airy and sparkling like CK10, it is there with right amount and detail. Due to its mid-centric character. E50 is way successful at lower treble compared to CK10, and by E50, I realized that my ears got tired of such 'almost sibilant crazy trebles' which gives pure satisfaction while listening to trance and cause 'hiss' sound constantly. Trebles of E50 are also not stretching up high as you understand, however it has a deeper stage than CK10. Again excellent cymbals, female vocals and other details. I really appreciate their success and love this way of Audio Technica.
All in all, this is a complete balanced iem with a tad forward mids, but not the warmest, also not far away from being analytical and cold. This may cause question marks in some folks' head. I'm just trying to make an another description of 'balanced', forgive me
This is absolutely an unforgiving iem in means of source and record quality. While I'm listening to new releases (still depending on their recording materials) and electronic stuff, it's not a problem but if you are listening to some old records and if you hate hearing 'mistakes'... bye bye happiness
Actually if the price was not an issue, this would have been my main reason why I avoid buying E70, though now I'm caught by E50. I really didn't expect to meet 'almost a complete studio monitor' at this price level.
If you are looking for some fun iem, stay away from these. But if you really want to listen to music as it comes out (or should I say 'in the way it is given to you'?), you should buy these. Especially jazz, acoustic, classical, instrumental lovers should do!
Apologizes in advance due to lack of information and grammar. I admit that it only reflects my own impressions in my very own and poor world of sound.