IMO, bass response is a subjective preference but IMO the default tuning is just right for me. I wouldn't even call it bass shy at all and IMO it's slightly lifted more compared to DF tuned IEMs such as the Etymotic ER2SR from what I recall. Bass dynamics ("how fast the on/off transients") is excellent and far better than HD 6XX ("smeared" transients). The star of the show to me though is the mids and treble which to me is definitely in the A+/S- subjective level. It's far better than Focal Clear OG (the word clear in the headphone is an oxymoron to me since its sonic presentation is not crystal clear sounding to me), and as good or better than the HD800S. Definitely on-par with HEDDphones (HEDDphones is superior in bass response for me than the Aeon subjectively and
objectively it has extremely low distortion in the bass frequencies as well), and I'd even go as far as closing-in to Focal Utopia's territory and some hint of E-stat characteristic to it as well, but the Dan Clark VOCE is clearly on another league of details, and Aeon 2 Open is better in "engagement factor" to me than the VOCE.
In short, I was grinning and headbanging whole time and such a bad timing that I get to critically listen to it during recession whereas I've heard the VOCE way back pre-pandemic times. I would go back to the store to demo it again over there next week but this time out of a 36dB SINAD amp just for schiit's and giggles.
I agree with your comments on the headphones I've also heard, and envy you on the many headphones you have heard that I have not. I gave up the chance to do that when I sprang for the DCA Closed X to Noire upgrade, instead of trying something with different strengths and weaknesses. I did it because I already so enjoyed the excellent tonality, separation and low distortion of the DCA planars.
A/B COMPARISONS OF NOIRE VS. CLOSED X HEADPHONES: I've been doing level-matched and EQ-matched A/B comparisons -- many of them -- between the Noire and Closed X phones, and am starting to add the HD6XX's to the comparisons. As you may know, the Noire and Closed X headphones are very similar, but the Aeon 2 generation of phones, which includes the Noire but not the Closed X, has a newer planar driver that was developed from the ground up. the Noire and Closed X both also have newer, perforated earpads. Further, the Noire has out-of-the-box tuning intended to enhance soundstage and "slam". The closed X's retail for $379-$499 on Drop.com; the Noire is $899 retail or $765 if you are a prior-DCA customer in the DCA Club.
I haven't finished my comparisons of Noire vs Closed X yet but I've got some prelim findings. The Closed X and Noire phones are obviously close kin and sound very similar. There are some specific differences that strike me as unambiguous. ("Unambiguous" = immediately obvious in sound-level-matched bi-directional A/B and B/A comparisons using at least three relevant music selections, albeit not double-blind. So this is still subjective, even if careful. I'm leaving out more subtle differences that are more likely to be subjective in a sighted A/B comparison. Here I'm also comparing the headphones primarily when EQ'd to the Oratory/Harman curve, although I also made some comparisons without EQ. Out-of-the-box and without EQ, there are differences in tonality. For EQ'd comparisons, I used Harman primarily to have an objective reference point. In real life, I modify the Harman tuning, touching up the lower bass, and restoring the Dan Clark bass "bump" in the 60-160 Hz region.)
The Closed X headphones don't have much if any soundstage unless the source recording has very well-recorded spatial cues from the source venue, and the musical image is usually between the ears. Drop advertises the soundstage of the Closed X, but I rarely hear the soundstage extend out further than the top of my forehead on well recorded material. That's not to say the headphones are less than enjoyable in many other ways. However, the Noire headphones do more consistently have a soundstage, especially for well-miked acoustical material. The Noire stage is often shallow and close, between 9 o'clock and 3 o'clock, but can sometimes have some real soundstage depth from 10 o'clock to 2 o'clock given good miking and a deep physical setting in the recording venue for voices and instruments. (I've experienced behind-the-head localization on the Noire with a mixing-studio-demo, but not with regular recorded music.)
In this respect, there is a bit of a preference trade-off involved between the Closed X and the Noire. If you are sensitive to soundstage and instrument image, the Noire can sound more natural on acoustic source music -- the sense of an array of instruments in real space with balance between instruments (as if listening from a position in an audience) is stronger, though less often dramatic. However, the "intimacy" of the Closed X headphones, particularly the close-in presence of vocals, can also be appealing, in the same way that closer-miking of a good voice can appeal. In an A/B comparison, it can make the mids of the Noire sound a bit more recessed, even if more balanced among instruments and well-placed in space. (By the same token, depending on the recording, some instruments or voices can seem too forward on the Closed X and perhaps more in balance on the Noire.)
Stepping back to consider this further, I mentally divide soundstage and imaging capabilities into (1) those that are based on spatial cues in the source recording; and (2) hardware or signal enhancements that introduce the impression of greater space or soundstage between the signal and the ear. The former would include simple miking techniques that capture delay/reverb from a given listening location, tonal differences such as a U-shaped frequency curve, etc. The latter would include open-back, angled drivers, and phase or other signal enhancements like cross-feed. The Noire exhibits the first case (showcasing spatial cues in the recording) and in my case, does more noticeably improve the soundstage when the recording earns it. The tonal balance, including recessed mids, really seems to work in giving me the feeling of being in the audience with a balanced presentation of all the musical forces. "Recessed mids" sounds like a negative, but when I set up two EQ's to A/B, one with normal Noire mids and another with higher emphasis on the mids, I am very surprised by how often I prefer the first, even with genres or performances where I woudn't expect it. (YMMV.)
That said, the open soundstage of the Noire may partly originate from factors other than the frequency curve. I still consistently prefer the Noire's soundstage even when both Noire and Closed X are both EQ'd to Harman/Oratory. I can't explain whether this arises from some inherent imprecision in EQ-matching using by-the-book Oratory EQ's on headphones that individually vary, or some other difference in the execution of the Aeon 2 design of the Noire vs the Aeon 1 design of the Closed X.
I would add that video-streaming with Noire phones very frequently produces a pronounced soundstage, perhaps suggesting some kind of ambience enhancement by NetFlix and the other streamers. (If anyone knows more about this, let us know.)
Both the Noire and the Closed X do a good job with instrument separation, with separation defined as being able to distinguish details of timbre and attack/decay among instruments in congested material with overlapping instruments. However, the Noire can sometimes do a better job sorting out the timbre of instruments with a long decay; e.g. a recessed acoustic bass line behind an ensemble of instruments. This also gives the Noire a feeling of better detail on some notes or instruments, as well as separating the instruments from others, simply because some notes or resonances seem to linger just enough to catch my attention on the Noire in an A/B comparison to the Closed X. It's sometimes notable, other times slight. The Noire does better when "separation" also includes locating instruments in physical space, although this is a psycho-acoustic phenomenon that may vary between people and also is affected by cues in the recording. Again, this is a preference item; some people may not be as sensitive to the physical imaging, or may listen to genres where it matters less. Finally, the Noire is simply somewhat more resolving in A/B comparisons, although both Closed X and the Noire taken separately are very satisfying on this score.
A difference between the Noire and the Closed X that I didn't expect relates to attack/decay with percussive transients. If you listen to electronica with the very common synthesized drum strikes and rim-shots, these transients often involve a very fast attack and decay with little resonance. With these transients, the Closed X often sounds extremely fast, like a sharp snap of high voltage electricity, while the Noire can sound more like a cross between snap and a handclap. If you then compare this to acoustic transients like actual drum strikes and rim-shots, or wood-on-wood sound effects, the Noire does better on picking up the timbre of the drum-strike spreading across the drumhead, or the timbre of the wood-on-metal rimshot, or the resonance of the wood-on-wood. I'm still working on this but the Closed X sometimes feels faster and snappier on percussive transients, and the Noire may be better on capturing the realistic decay of acoustic instruments, including percussive transients. Whether this simplistically translates into across-the-board better "slam" for the Closed X vs greater resolution and separation for the Noire isn't clear yet; I will do more comparisons with more instruments and music when I can find the time. [PS months later: both Noire and X can have snappy attack on percussive transients. The Noire, I believe, simply captures more resonance on the decay and sustain for acoustic sources, while the X is a little more damped.]
"Does it make sense to upgrade from Closed X to Noire?":
1. if you want bang-for-your buck, the Closed X gets you most of the undistorted bass, resolution and separation of the DCA Aeon series headphones at a much lower cost, especially if you aren't that sensitive to subtleties of imaging and soundstage, or if you don't listen primarily to acoustic material.
2. On the other hand, if you really know that you appreciate the DCA headphone sound, listen to acoustic sources, and tend to perfectionism even at a cost, the Noire may be worth it, especially if you use the DCA Club discount.
3. This choice kind of depends on your "listening style": if most of your listening is "experiential"; that is, focused on the music, you might not notice the difference in the phones much because their virtues are mostly shared virtues. But if you are often also an "analytical" listener who mentally dissects your audiophile experience, then you may sensitize yourself to the real, albeit modest differences between the headphones.
4. Finally, there seem to be some listeners (and I am one of them) who dislike having their music located between their ears most of the time, whether or not they also specifically crave a large soundstage with precise imaging; and the Noire will be preferred for them.
5. Oh, and the portability of the Noire is a real plus if you use them mobile (which I do daily).
As noted earlier, these comparisons are based primarily on both headphones being EQ'd to Oratory/Harman. (Exception: some soundstage comparisons involved native EQ rather than Harman EQ.) Without EQ there are other tonality differences and it is worth noting the 60-160 Hz bump in the out-of-the-box Noire headphone FR to modestly increase bass and perhaps "slam" in a frequency band in the upper bass that also often sports drumstrikes and other percussive transients. But both headphones share extremely clean, undistorted and pleasant tonality down to the sub-bass and some brightness without EQ. You can EQ them easily or use the supplied earpads to adjust FR.