First of all I'd like to mention that my previous DAP was Sony X1050 and this review mostly will be loosely based on comparison with it.
 

 
 
 
UI and features:
I don't want to talk much about features and user interface. UI is pretty simple and responsive, slow at times. Coming from x1050 finding tracks takes much more time and while still good overall UI and navigation is nowhere as good as sony's, no surprises here.
Another clear downside from walkman is battery life which is still more than 20h after 6 years of using on sony, twice as much as X3 II. 
Bugs:
Couple of times when the player was in a sleep mode it was producing very loud hiss in left headphone which caused battery drain. After connecting to pc the problem disappeared.
Even though in the menu u can change it, in the list it always shows file names rather than title of track. I hope I'm doing something wrong and there is a way to change it.
 
Sound Quality
I compared sounds with no EQ or any sound effect applied on any of the devices. Volumes matched by my ears. Gain setting was low and it was tested with easy to drive headphones (<48 ohm). Since the differences in sound signatures is very big there was no point of performing blind test.  This section of review is very much depended on my personal taste.
 
Overall sound signature / Details:
Sound signature is quite neutral, it is neither very warm or too digital. Compared to Sony x1050 it is colder with more open sound. Vocals are farther than I'd like, in my opinion it doesn't allow you to feel enough emotion from the singer and uniqueness of voice of artist is kind of lost compared to sony X. Instruments sound very clean and detailed, well separated from each other. Though there are things for what I prefer x1050. On Sony you can almost feel the smell of wood when listening to acoustic guitar or violin, When listening to Violin Concertos of Mozart on X3 II you feel like you are sitting near the stage and on x1050 you feel that you are the one who plays violin, if it makes any sense. In one word sound signature of sony is more Organic or more Analog maybe (costing little bit of soundstage though).  
In noisy environment I had to push volume up on Fiio compared to sony because walkman's forward sound signature doesn't take your attention to background noise as much as fiio's open sound.
Soundstage
One of the most important part of the sound for me is soundstage and X3 II performs very well in this regard. It is very wide and uniformly distributed in the space. It is much wider than sony though it never comes as close to ears as walkman does, but overall soundstage is a noticeable improvement over Sony.  Imaging is also better than x1050 and if it had little bit more forward vocals I would rate the soundstage as excellent for my taste.
Bass
Bass quality is quite good, it is very clean and fairly textured, though it doesn't extend as much as x1050's bass. On sony bass is little bit more forward with more punch and better extension with a noticeable margin. On the other hand Fiio has more clarity better texture and faster midbass. 
Mids
Mids are very clear and colorful, has little bit more clarity than x1050 and again it is little bit laid back similar to vocals (which is kind of part of mids anyway). What I liked was how it performed in upper mid section, which didn't have any harshness was bright enough and caused very little sibilance even with sibilant IEMS.
Highs
High extension is remarkable, it isn't brightest DAP u can find but it has very well controlled smooth treble with sufficient sparkle. Compared to sony highs are less present and also less grainy but extends bit more, on x1050 highs are little bit boosted which causes more sibilance with some headphones compared to fiio. So overall highs are very enjoyable and detailed with almost no grain.
Noise floor
I know some people say there is noticeable hiss but since I've been listening to very "hissy" sony for 6 years there is nothing to complain about. Fiio has much, much less noise which is barely noticeable for me even with fairly sensitive IEMS. I have to admit that I was always surprised that people were complaining about noise floor because I didn't care about it even on my walkman but now that I got used to clean background of X3 II the hiss on Sony kind of bothers me when listening at complete silence and darkness (yes, darkness is very important for feeling sound quality for me).
 
EQ/sound effects
The problem with EQ is that once you apply it the volume drops significally so it is hard to say how much it affects quality (in case of sony EQ decreases soundstage and extension of treble). One thing I can say for sure is that sony's clear bass has more pleasant impact than fiio's 6 DB equalizer. Anyway I don't think difital EQ is good enough nowadays for audiophiles, what matters for most of us is an untouched clean sound.
 
Amp section / Conclusion
As I mentioned all my headphones are easy to drive and I couldn't see advantage of fiio X3 II over x1050 in that regard, volume level on low gain is exactly the same as Sony's (bear in mind that Fiio output impedance is much lower i.e. it needs more power to match volume of sony), so other than much less crosstalk and background hiss there are no other advantages of amp power for me (probably there will be if I buy high impedance headphones). Before buying I also was considering Sony A15 but decided to keep my x1050 and buy fiio for little bit diversity.
 
Considering the fact that it is almost in same class that X1050 was 6 years ago I expected little bit more from X3 II. The sound quality overall is better than of Sony but there still some aspects in which I prefer sony's sound  and overall difference isn't big enough considering that you lose some features and versatility of UI.  All in all The DAP is excellent for it's price tag 200$ in US but it isn't as spectacular for the price I had to pay in Europe (235 Euros).
 
Overall, excellent built quality, great accessory pack, big soundstage and clean sound guarantee the success of the player.
 
I tested sound mainly 44/16 WAV (since sony doesn't support flac) and 320kbps mp3 (still perfectly enough for testing sound signature), for diversity the player was tested with songs of Radiohead, Iron maiden, Tool, Mozart, Eminem, Katie Melua (for female focal tests) and so on...  
Thanks for reading...

 

 
Hi, My last headphones before these were sony XB90ex, so my review will be loosely based on comparison with xb90.
Firstly since I paid $50 more than xb90ex (95$) my expectations were bit high. xb90 had 16mm driver and I really liked it and the second I put h1 in my ear and pressed "play" I felt that they were small 9mm drivers, don't get me wrong, I didn't literally feel the size of the driver but it has somewhat thinner sound, the sound that you can tell it comes from earbuds, which wasn't the case when listening to xb90.
 
Soundstage:
xb90 had huge soundstage so the first thing that disappointed me when I tried XBA H1 was the soundstage. while it's still larger than low-priced headphones(< 70$) it is nowhere as wide as xb90's (though it's better than ex310's). Even though the sound is pretty much front oriented it still never comes very close (I like when sometimes it feels like sound comes inside your brain), neither it goes too far, so i'ts kind of 2D.  On the other hand instrument separation is very good, I would say better than xb90, highs and lows don't distract each other, I think 2-way drivers have something to do with this. Overal I'd say that soundstage is pretty flat, when I listened to xb90ex after these it was like returning in heaven after living on earth for a while.
 
Bass:
compared to xb90 subbass somewhat lacks, generally bass is good and high enough for me and majority of listeners but that subwoofer feeling of xb90ex is gone. Good thing is that it is by no means under or overpowered. Bass texture is decent, Midbass is punchy and fast, maybe bit better than xb90's. 
Overral bass performance is slightly inferior compared to xb90's.
 
Mids:
Mids are definitely front-oriented, bright and very clean. Female vocal is real joy to listen. I think generally this is the easiest area for IEMs to perform and there is no point to talk much about it. In one word, mids are very pleasant to listen.
 
Highs:
before burning in, highs were harsh, bright and there was sibilance, after burn-in the harshness smoothed and sibilance faded away (not completely though), in fact it got too smooth for my taste. Arguably inferior performer compared to xb90ex in this area, which had fairly smooth but bright treble. The good thing is that it's smooth and quality is good, it's just not bright enough for me, it feels like it cuts frequencies above 12 KHz.
 
Amp:
I used them on my walkman x1050 which has great sound quality regardless its age. Since the impedance of the headphones is 40 OHM which is much higher than most earbuds (majority have 16-24 ohm) I thought amplifier would be necessary but the difference isn't that much, Even without amp these earbuds sound decently, Though the sound is somewhat hollow, with amp it gains some midbass and sound gets more full.
 
Conclusion:
Overal these earbuds are noticeably cleaner and more detailed than XB90EX but flat soundstage is dealbreaker for me. When you listen to these you don't feel anything special, I mean it doesn't have specific signature like XB90 which has very 3D sound with excellent subbass which is very much like bass of expensive overhead headphones.
Xba h1 earbuds are good but very overpriced IMHO. I would take xb90ex over H1 without any second thoughts, they are overall as good performers and much cheaper than these. I think real price of these should be at most $100.
One more thing, the left headphone is slightly quieter than the right one but I'm the only one who notices it but still it drives me crazy. I played with balance on PC and measured around 0.8 db difference. I thought it was my units fault but then I so test on goldenear and there was the same situation.
This review maybe was too critical, they're not bad at all, at least instrument separation and clarity were excellent for the class.
I was planning to write bigger review with photos that I spent much time to take but unfortunately the editor doesn't allow me to insert them.
Thanks for reading.