All you guys... please, please stop fretting about firmware 3.0.
It is - in my humble opinion - the most 'correct' sounding firmware for the X3 yet. And soundwise it is a huge step from 2.1 to 3.0 and a smaller step from 2.14b to 3.0.
For all the doubters, here is a little summary:
Sound of 1.x - 2.1:
- flat and constricted stage, soloists seem to take a few steps back from the microphone
- diminished upper bass, mids and lower treble -> leaving deep bass and high treble
- dynamics suffer from muted mids
- far from the original sound of the files it plays
- perceived frequency response feels unbalanced
- not very colourful sound, definitely not audiophile
Sound of 2.14b - 2.xxb:
- holographic stage
- stage is slightly instable, instruments move around a bit
- less deep bass and high treble - because upper bass, mids and lower treble are back
- much more balanced perceived frequency response
- more details
- perfect dynamics with some slight added aggressiveness
- very colourful sound
- some slight 'glare' at high mids / low treble
Sound of 3.0:
- holographic stage with correct dimensions
- stage is completely stable, instruments are 'glued' to their places
- perfectly balanced perceived frequency response (maybe there´s a touch of warmth)
- the same amount of details as before - they´re just not so much 'in-your-face'
- perfect dynamics
- neutral sound
- glare completely gone
In short, after firmware 3.0 this simply is the best portable player I own. And I own many, which, in some cases, have been superior to the X3 before (using firmware <2.1). I have no idea, how FiiO could change the sound without me being able to measure it but it´s a fact that they did. And the improvement is so huge that I feel that every review written to this day should be rewritten... because they´re all wrong now.
The X3 now is not only the best DAP I have, it´s also one of the best sources I have. There´s only one device that´s better: the Xonar Essence STX. And the difference is not that big. This truly is remarkable, especially after I considered selling it until a month ago because of its mediocre sound quality. Firmware 2.14b already shattered the idea of selling, firmware 3.0 crushed it completely.
IMO, Astell&Kern, iBasso and Sony can pack their bags. And FiiO too... because, in all honesty... I feel that the X3 is superior to the X5 (judging from what I´ve heard when I had the preview model).
When not talking about sound the firmware has so far been a delight. Fast, responsive, free of bugs. If there´s one thing I don´t like too much it´s that the cover art is resized to (I assume) 300x300 px and cropped because it doesn´t fit. But that´s it.
Very well done, FiiO.