This and That:
Comes with a really nice storage case that is however not spacious enough for the headphone with attached cables (unfortunately that's true for many manufacturer-provided storage cases (not enough space for the headphone with adjusted headband and/or attached cable); I like about my Sennheiser HD 800's and HD 600's case that they are spacious enough for the adjusted headphone with attached cable).
Comes with felt and foam tuning inserts to fine-tune the treble quantity to one's tastes. Easy to install and remove (they're just placed in the cups and removed easily; they will of course reduce the space inside the ear cups if installed). I'm not using any of them.
Cable decent but I don't like that it's fully sleeved with fabric (I'm generally not a fan of fabric-sleeved headphone cables).
3.5 mm plug on the cable's end and what I think are locking Hirose 4-pin connectors on the headphone's end.
I really like the design with the (genuine) carbon fibre faceplates and metallic blue paint. Quite unique and beautiful design and different from other manufacturers. I really like it.
Really high build quality.
At first I thought the headband had the same automatic height adjustment mechanism as my AKG K701, but it turned out to be a traditional, simple sliding adjustment mechanism. As the sliders sit rather tightly, it is thankfully rather unlikely that the headband height is adjusted inadvertently.
Soft ear pads. Clamping force neither too tight nor too loose for my taste. Very high comfort.
Good noise isolation.
Sound:
Low impedance sources (my RME ADI-2 DAC for stationary listening, mainly FiiO Q5 with AM1 module for PC listening), no felt/foam tuning inserts.
For what it's worth, I have got hair on my head and in my face.
Tonality:
Neutral with gentle sub-bass elevation.
Excellent tuning, extension, evenness and timbre. Beats a lot of other established headphones in these areas, and is comparatively fairly and reasonably priced for what it delivers.
The lower midrange and fundamental range is absolutely flat and doesn't have any hint of warmth (the deservedly popular Sennheiser HD 600 that is also among my all-time favourite full-sized headphones is somewhat warmer in the root and lower mids); here the AEON Closed really aims for uncoloured flatness similar to the Etymotic ER-4S or ER4SR.
While the upper bass is still flat, which is also mostly true for the high midbass, there is a moderate lift in the low midbas and true sub-bass (that lift is kept upright down into the very low sub-bass at 20 Hz without any roll-off) that adds just a bit of fun to the otherwise neutral lows when the recording extends this low (therefore its lows somewhat represent a fusion of the ER4SR (upper bass, root, lower midrange) and ER4XR (sub-bass, (lower) midbass)).
The mids are mostly neutral with a moderate recession in the upper mids/presence range, so there's no hint fatigue or exhaustion, but without being subdued or sucked out either. The timbre is natural.
The middle treble is a little in the background compared to perfect neutrality, but very even and realistic, with an upper treble response that is neutral again.
What's really charming about the treble response is how even and realistic it is; it lacks any sudden, unnatural peaks or dips and is very even - therefore, it is clearly ahead of my HD 800 in terms of timbre, realism and evenness, especially in the treble, and extends lower and more linearly in the lows as well.
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So yeah, tuned extremely well and evenly. And sounds mostly neutral. Great timbre, extension and evenness.
Resolution:
The AEON Closed is a detailed and well-resolving headphone, however its bass response is a bit untypical for planar magnetic headphone standards, as its lows are somewhat on the softer and also bit slower side, more typical of several dynamic driver headphones (it's not really sluggish yet, but definitely not as tight and fast as the lows of my HiFiman HE-400 or the ADVANCED Alpha, and my Audeze LCD-X that's generally a planar magnetic headphone with a somewhat soft bass response as well is a bit tighter in comparison, too).
Other than the bass that's on the softer side for planar magnetic standards, it is a headphone with really good speech intelligibility, fine treble details and really good and clean note separation as well as good bass details.
It may be ultimately not fully as technically profound as my HD 800 (e.g. tightness, note separation), but comes more than close enough for me, and is especially superior for me personally as its tuning, neutrality, timbre and bass extension linearity are (clearly) superior to the more expensive open-back dynamic driver headphone.
Compared to my HE-400 and the Alpha, my AEON Closed is also the more resolving as well as better separated headphone in the mids and treble (and has got the more realistic timbre as well, especially compared to the HiFiman), and therefore also ultimately outperforms mid-priced open-back dynamic driver headphones such as my Sennheiser HD 600, Beyerdynamic DT 880 Edition 600 Ohm or AKG K701.
Soundstage:
Surprisingly, the AEON Closed doesn't really sound like a closed headphone. It doesn't have the limited soundstage size, boxy feeling, lacking openness or mild reflections that most closed-back headphones have, and it doesn't suffer from the rather small soundstage that most planar magnetic headphones, such as my Audeze LCD-X, HiFiman HE-400 or the ADVANCED Alpha, produce, either, but sounds spacious, open, three-dimensional and large.instead.
To make it short, it doesn't appear like a typical closed-back or planar magnetic headphone at all when it comes to soundstage.
The imaginary stage is quite large and expansive - not as much as the huge stage of my HD 800, but it clearly leaves my head and expands towards my shoulders, with spatial depth to match, even though it is ultimately somewhat more oval than circular, wherefore it is a large, open sounding soundstage that is definitely not limited at all.
The imaging is accurate and precise; instruments have a well-defined border.
The layering capabilities of the AEON Closed, along with the separation, are good as well, wherefore it creates a three-dimensional, authentic soundstage.
Conclusion:
Not perfect but very close to it wherefore it has replaced pretty much all of my other open-back full-sized headphones for stationary listening.
In the past I haven't used any of my closed-back headphones for stationary listening at home as I didn't fully like their soundstage presentation for that purpose/listening environment - well, since I bought the AEON Flow Closed, I am indeed using a closed-back headphone for stationary listening, and thankfully it doesn't sound like a typical planar magnetic or closed-back headphone at all.