This is a review for the 900s (using an iBasso DX90)
 
My dear and beloved triple fi 10 died recently, after 6 years of intensive use and a fair amount of abuse, So well done UE, and thanks for the worthy investment. 
 
After looking at a dozen of potential candidates for replacement (Shure, even the UE Pro 5, Seneheiser IE80, etc,) I decided to have a go at the UE 900s thinking "if no good I will return them". Well they are definitely staying with me! This review is mainly a comparison with the Triple fi 10.
 
I read in a review, that the UE 900s were a more mature version of the Triple fi, and I think that is the perfect summary.
As listed in the Pros of this review, the UE900s are just .... better than the triple fi 10 in almost every respects (soundwise). And I really really liked, the triple fi 10: But the UE 900s are better and I would also add that they are as much fun to listen with! 
 
I started my IEM journey with the super fi 5 Pro (I am not a UE sales rep btw) and they were awesome but lacked bass and were sibilant to the point of becoming painful sometime.
Then I got the Triple fi 10 and this was honey to my ears! The bass was deep and rich and impactful and gone was most of the harshness in the high end (still some).
But when comparing the Triple fi 10 with the Super fi 5 Pro (still going strong after almost ... 10 years!!), I did realize that the mids were very recessed indeed. Also with some album/recordings the Triple fi 10 boosted bass was getting tiring to listen to and resulted in an unbalanced/artificial sound.
 
The UE 900s are much more balanced and fix those two downsides that the Triple fi has: The mids are more present and richer, and the bass is less prominent and at the same time more textured. This results in a significantly smoother and more fluid sound. There are two other areas where I find the UE 900s better: The soundstage is massively improved, and the layering of instrument is much better: I can more easily isolate individual instrumentsin the soundscape than I could with the Triple fi 10.
Because of the additional clarity I also find myself listening to music at lower volumes levels. 
 
Many reviews praise the accessories coming with the UE900s. Well I dont agree at all and think it is a very poor selection; The IEM come with tons of tips, ok, but no cleaning tool, not adapter, no attenuation plug (for use in planes), and a lousy and totally unpractical carry case, which design seems to be an after thought. For info the case of the triple fi 10 is absolutely bashed after so many years of use, but way way much better than anything I ever had earphone delivered with. 
 
Few other things I personally think could be better are 1) the cable: you get two ot them, ok nice thanks, but I will probably need both because the braided design seems very weak and will probably fail sooner rather than later. The cable also tangle A LOT. Not to mention that the remote does not work with Android devices (I am fed up with this apple/iPhone electronic dictatorship) although you can step to the next track by double clicking the middle button. The volume buttons cannot be used at all.
 
2) the swivel connectors make it difficult to manipulate and fit the earphones. I could fit the Triple fi 10 in the dark with one hand, walking in the crowd or in a shaking plane without problems. I sometime feel it is like a mission to fit the 900: untangle the cable, spot the right hand side unit (the little red ring does helps), rotate the connector and maintain it in place while fitting the earphones .... I will get better at it, but it is awkward.
 
Comfort wise, I had absolutely no problems with the triple fi. but the flush design of the 900 is better aesthetically. However there is more shell in contact with the ears' skin, which means more cleaning to do and possible more chance of having the odd pressure points. 
 
So in short, I am almost glad the Triple fi gave up on me. I did like them because I have been using them for so long but I think soundwise the UE900s are definitely a step in the right direction. I am very happy with the replacement especially now the price is so low (less than 190 UK£). To summarize the difference and If you like paraboles, soundwise the Triple fi 10 are a BMW, the 900s are closer to a Mercedes. Classier, more mature, smarter. and considering the glorious reputation of the Triple fi 10, UE/Logitech have done a very good jobl.
 
I will definitely look for a replacement cable/remote and then keep enjoying listening to all of my tracks again and again! And maybe buy one of those awesome UE small case to house my new sound companions!

I bought the Dx90 to replace a HifiMan HM601 player. Main reason was that I needed more storage (HM601 only takes 32gb cards). And I though this is a good opportunity to get a better player overall. Well, it is sort of what I got.

(see update in paragraph below)
Quote of my previous appreciation of sound quality:
Sound wise, I honestly struggle to ear any significant difference with the HM-601. Tried switching between both using 16bit FLAC files and both UE triple fi 10 and Sennheiser Momentum over hear and honestly the sound quality and sound signatures are very close. i.e. rich, warm and very dynamic. After some burn in (30 hours) the DX90 seems a little brighter and more open, but only very slightly. I don't have any 24 bit FLAC to test though (the HM601 only takes 16 bits). But overall, given than the HM601 uses a single old DAC (Wolfson) and costs half the DX90, I really dont see all the hype around the dual Sabre chips.

####### UPDATE!!! After writing this review I though I would carry the test again (of listening o the same track/earphones on both the HM601 and the DX90. The DX 90 has now 30 hours of listening and I went through two battery charges using the burn in cable provided. And ....

WOW .... I am absolutely blown away by how different the two player sound now! The DX90 now sounds open, airy with a huge amount of texture and details across all the frequency range ... just unbelievable. I have never been a believer of the burn in effect but I have no other choice but to admit this phenomenon is indeed real at least on this device. The HM601 sound dark, heavily veiled in comparison .... I am just amazed so much that I go back to more listening right away! ######

Build quality is clearly better that the HM601 and very good in the absolute: good size/ratios too so a very pleasing device to handle. However the switches lack crispness especially the one for the gain that often get in between positions.Other than that, not much to say on build quality.

Now it is all nice to have a touch screen (which is quite nice and responsive by the way) but what is the point of having a touch screen with such a simple minimalistic software and UI???? The HM601 had twice as many options and functions as the DX90 and I can tell you that it was not much. But the DX90 is pathetic in this respect: no file operation (I crave for a file delete), no track tagging (the HM610 had a ranking function), etc. And the font used by the default firmware is just plain ugly (thanks to Lurker for the modified firmware), and there is a lot of wasted screen space from the ugly icons at the beginning of each files.

Nice touches are the provided silicon sleeve and the screen protectors which makes sens for a portable player and already saved my screen. The battery is another average point of the DX90 because it only last about a day of on and off listening, overall not as much as the HM601. The DX90 could drive the sennheiser momentum really well although they are not particularly high impedance. So overall, a nice player and a good deal if you get a good price. However I cannot say i am blown away.

NOTE:

See update above --- After some more burn in the sound seems gets much much better more and more refined, better clarity, better texture better soundstage, better everything.
I dearly miss the analogic volume control of the HM601. Digital volume controls just suck in general