Hmm...
I'm curious how the Westone 4 would compare to the CK100.
Why you might ask?
I own the UM3X and the CK100 and have used a majority of the other high end earphones (although no W3 nor the newer SE535). For a Westone like sound, the CK100 has been the only other eaprhone that I've used that seem to use the same/similar drivers for a very similar presentation of sound. I basically see the UM3X and CK100 as brother and sister. The UM3X is huskier, more muscular while the CK100 is more delicate and chearful, but the core presentation is presented in a similar way, more so than any other earphone. The CK100 sounds nothing like the CK10 or CK90Pro but moderately like the UM3X.
Now I see the UM3X as warm and bassy. The upper midrange is recessed which creates a bass driven signature. It's mostly a bass shelf, very flat, limitless in extension, and balanced but slightly heavy and always overshadowing. Mids sound natural but overshadowed by the lows. Treble rises and matches the bass level but this creates a peak after the drop in mids which can at times sound quite colored and oddly emphasized with certain information. The top end sounds rolled off, not super extended (limitless) like the Triple.Fi 10, RE252, CK10. EQed, the UM3X gets significantly better and more balanced, but the treble doesn't carry quite the same energy and presence as the low end, and the treble driver doesn't seem to be the best pick of the litter to cover the spectrum(likely less of a need due to the UM3X being geared as a tool rather than consumer music. The level of detail, dynamics, and texture are quite high. Sound has a sense of power and presence that is largely unmatched by most other earphones. One thing the UM3X does really well is both show sound and the absence of sound, something most earphones can't pull off. It is pretty stark in what it shows you. If the source information is flawed, you will see it clearly. If there is noise or hiss, it's noticeable. Basically it is super revealing. The sound stage is in your face pulling you right up on stage so to speak, very wide, great depth, but you feel very close.
The CK100 is significantly more balanced. It sounds very even, more musical. The low end is more subtle of course not being dominant, but bottom end carries presence, impact, and extension. It's actually still different than an EQed UM3X, but it's more similar than different versus most other brands/models. Something like the Triple.Fi 10 provides more punch and a fuller note but also less depth on the very bottom end which loses some of the visceral sense versus the CK100. The midrange is flat which brings out the upper midrange making vocals natural and lively. Female vocals really sing. It's not midrange peaky like the SE530. Treble is well balanced and extended, a gentle sloping hill around 10kHz but nothing like the sharp 9dB cliff of the CK10 or mountain of the Triple.Fi 10, mild enough where tip choice can get you where you want. The treble has a "refined" sound to it, controlled, open but not super edgy or with too much bite, less raw energy than say the Triple.Fi 10 or RE252. The big difference in overall presentation of sound versus the UM3X is that the CK100 is less textured. It carries less articulation and isn't as stark as the UM3X. The note is still hearty and largely presented, especially for a BA based product, but it doesn't flesh out the note as significantly as the UM3X. The presentation becomes slightly more delicate from this. The sound stage proportions are better with the CK100. It's more rounded, natural. Both have good pinpoint placement, but the CK100 sits you farther away in what sounds like a much more appropriate distance. I always feel that sound stage requires good note texture. We need those subtle variations to really flesh out the space, placement, distancing. The UM3X is relatively aggressive and forward but sticks sounds in an exact spot, good enough where you could almost break out the tape measure and tell a person how many feet every sound is from each other. The actual shape of the sound stage is skewed though, close and wide. The CK100 has less texture but is very clean in details. Placement is pinpoint, but space isn't fleshed out as completely. The presentation is more balanced and does make the sound stage space more correct though. The CK100 is sort of a partial step towards the SE530 in a way. The SE530 had pinpoint placement due to a super clean note. However the SE530's note lacked texture (very short decay, familiar "BA" sound, which made distancing and sense of space very poor. The CK100 is a partial step towards this, but the notes are still hearty and well bodied rather than thin and analytical like the SE530. The CK100 thankfully also doesn't sound unnaturally laid back (for what is an extremely dynamic earphone) from a high lack of note thickness like the SE530. Instead, the CK100 sounds more delicate in signature but still natural and well-bodied.
From the way the Westone 4 has been described here, it seems to step a lot towards the CK100. It is better balanced than the UM3X and Westone 3. It is more laid back than the UM3X, hinting at a little less texturing or less dynamic range. The midrange and treble are much improved pointing to better balance and extension, like the CK100 has over the UM3X. The Westone 4 has lighter bass (more balanced with mids) but retains good punch (retains note heft) which the CK100 does also. In the end, I am quite curious if the Westone 4 ends up being quite similar to the CK100.