So, I sat down today with all the three headphones I currently own and proceeded on to compare them on a couple of my favorite tracks, dipping into other media as well.
The TL
R takeaway is that the HEX has a beautifully soft, marshmallowy sound, with a nicely enveloping (sub) bass and some body to boot, but an overall presentation which might not be ideal for every single track or occasion.
To break this into a lot more detail, let's start with the bass. The HEX has a very tasteful sub-bass that sounds nicely potent but well integrated with the rest of the frequencies. It gets a little softer as we move higher up away from the sub where some of the softness of the sound takes away a bit of the punch in mid and high bass, but still preserving good weight overall. The degree of which this actually has effect is song dependent; songs where bass is focused lower sounds marvelous (including sub in movies and games as well!) whereas where a tighter, higher and punchier bass is needed the HEX stumbles a little. In comparison, the 4XX has a tighter, punchier response with less impressive sub-frequencies and overall weight. The CB-1 is pretty much all bass, all day, every day, as much as you want. It is not complete bass-head, but it is very tastefully tilted, with decent tightness and great heft.
Mids continue to be deliciously smooth with the EdX. instruments sound very inviting with a tiny bit of warmth to them, but very realistic feel as far as body and timbre goes. Instruments that rely on attack however, are softened to a degree (guitars, aux percussion are most obvious) and lose a bit of presence in the mix. Vocals either sound excellent (when mastered neutral - bright) or soft, lacking in plosives and syllables (when mastered dark). In general, bright mixes sound excellent, while dark mixes usually lose too much energy on the HEX. In comparison, the HE4XX and CB-1s have more energy across the mids but also sound less even. They both sound best with darker to warm-ish mixes and in general guitars and perc never lose energy; if anything, it can sometimes get overbearing.
The treble is very well done on the X IMO. I don't perceive any deficiencies that would strike me, and they can sound nice and airy when a recording has that. They do still impart some softness up there as well, so instruments that have harmonics into the highs and cymbals lose an additional bit of presence there. The 4XX and CB-1 are on the treble happy side in comparison and they have no problem extending high, with the HE4XX more so having a certain sheen to things which can be either a curse or a blessing, depending on recording.
In regards to soundstage, the EdX deviates a lot from the other two as far as it is portrayed. Whereas the 4XX and CB1 have decent width but lack depth and height, the X is the flip-side of that, somewhat limited in width but very deep and high. This either sounds great or not so great. In some songs I still get a fairly spacious, well-rounded experience while in songs that are recorded to sound intimate or just don't have much width, the image collapses inward to the center a bit. It is certainly a different experience from my two budget headphones, though so far I am not sure how I feel about it and I probably prefer more width over depth when all is set and done.
Separation of sounds is generally excellent on the HEX, save for those songs that don't have even panning distribution. The experience is generally very detailed but wholesome and showcases a lot of the strengths of the headphone; that is a very smooth, breathy and musical presentation that is very easy to enjoy. The HE4XX does reasonably well in separation and so do the CB1 but it is nowhere near as effortless or natural as the HEX.
Finally, the timbre of the HEX then is one of flow, naturalness and musicality. It is virtually impossible for the headphone to sound harsh and it can bring some gut to the bass too which makes it great for movies and games (getting used to the staging does take some time) as well. The HE4XX is mostly reference sounding, but has nowhere the smoothness or overall finesse of the HEX and can get bright and edgy. The CB1 has great grunt in the bass and brilliant focus in the treble, but can sound a bit splashy (not unlike the HE4XX) and nasal in the mids, with a bit of a V-curve to the presentation.
In terms of value, the HEX certainly brings something new to the table that neither of the other headphones have, though I find myself wishing it imagined closer to conventional headphones which might be my main issue with it, with the somewhat selective dynamics possibly tied to this in a way (being focused more inward than outward).
As things stand, I am still not quite sure whether the X stays or goes. I will continue to listen and will update you guys accordingly :]
UPDATE - soundstage shenanigans should be disregarded. Almost all my criticisms disappear by switching back to the stock cable... The details don't stand out as much anymore (more diffuse before) but the tonality is awesome!
UPDATE 2 -with the stock cable, it is almost like a different headphone. Bass now punches rather well, there are improved dynamics, the vocals have a tiny bit more edge to them too, but they're still nice and smooth... I think I learnt a big lesson about cables today and honestly, it almost made me sell the headphone because of that. Really glad I did not.