Fit and Comfort

Seen above is the Drop + Dan Clark Audio Aeon Closed X placed on a mannequin head to help show how these headphones would look on the human head. Note that the head is slightly under average sized, so account for the discrepancies accordingly. As with all headphones, getting a good fit and seal is crucial, so make sure to properly use the various pivot points, and the height adjustability of the headband and ear cups. This section is mostly a summary of the points expanded upon in more detail on the previous page, but I will point out that the Aeon Closed X weighs 326 g, which is absurdly low for a set of planar magnetic headphones. Part of this is due to the use of smaller, single-sided magnets but then there's also the svelte headband and plastic frame contributing. It's a very comfortable set that I enjoyed using for long periods of time, although I would have preferred the clamping force to be slightly higher on my average-sized head. This, combined with the pads simply being stuck on, meant I unconsciously kept wanting to press the pads inward to test how good a seal I had, only to realize it was fine. Passive isolation isn't the best here though, with minor two-way sound leakage occurring in use. I mentioned before how the ear cups and pads are both shaped to fit around and over your ears naturally and it thankfully does not go overboard as with the likes of HIFIMAN with its teardrop-shaped cups. Once you get the headband sized properly, this is a set of headphones which can be easily placed over your head in a couple of seconds. The suspension band can possibly be irksome if you find it shifts around on the top of your head, but you can tighten it further at the screws on either end. I'd also avoid using these outdoors much in the absence of any rated dust or spill resistance.

Audio Performance

Audio Hardware

I'd point to the DCA Aeon RT product page for more details about the driver platform that's been used here on the Aeon Closed X. Dan Clark Audio uses an in-house designed and manufactured, proprietary planar magnetic transducer with a relatively small diaphragm at 62 x 34 mm compared to the usual circular 90-110 mm drivers employed elsewhere. DCA claims the diaphragm is thus quite light and the transducer as a whole is efficient enough to where a single set of magnets will suffice to drive it, thus helping keep the headphones weight down. There's also the use of its patented V-Planar technology and first-gen TrueFlow motor optimization, which you can read more about here if interested. The newer Aeon 2 has updated tech but also costs more, to where I appreciate the Aeon Closed X/RT still being a thing. Drop and DCA also claim individually matched drivers used here with an impressive 0.6 dB matching from 100 Hz – 8 kHz! The Aeon Closed X is one of the more demanding headphones on the market though, with a typical planar magnetic characteristic of low impedance (12.5 Ω) and low sensitivity (91 dB/mW) making for a current-hungry set. I would have rather seen Drop go with the XLR DUMMER cable rather than this single-ended version, although a decent DAC/amp can still easily drive it. Between the power requirements and the 2 m cable, I can't say this is the best solution for portable use out of the box at least—maybe if you had something such as the FiiO Q7.

Frequency Response Measurement and Listening

I will mention that I have a general preference for a warm-neutral signature emphasizing a slightly elevated bass and smooth treble range, with detailed mids and good tonal separation. I also generally prefer instrumental music over vocals, with favored genres including jazz and classical music.


Our current headphones test setup uses a set of two custom in-ear microphones for the two channels. These microphones closely adhere to the IEC711 class, but have been tweaked to be more reliable in the >10 kHz frequency range, the precise issue with my previous setup, that is otherwise still very good and will continue to be used for IEMs and earphones. Two soft silicone pinnae are installed on the sides, separated by a distance matching my head, and multiple "height" adapters have been 3D-printed for further customization, based on fit, head size and shape. Each set of microphones has an XLR output I separately adapted to 3.5 mm. I used a transparent source—the FiiO K9 Pro ESS—for measurements, after confirming it was not a bottleneck in any way.

This artificial head simulator feeds the microphone lines into a reference USB sound card, which in turn goes to a laptop that has ARTA and REW running. I begin with an impulse measurement to test for signal fidelity, calibrate the sound card and channel output, account for floor noise, and finally test the frequency response of each channel separately. Octave smoothing is at the 1/12th setting, netting a good balance of detail and signal to noise ratio. The default tuning was used for testing, and no app or program-based EQ settings were chosen, unless specifically mentioned. Each sample of interest is measured at least thrice with separate mounts to account for any fit issues, and an average is taken of the individual measurements for statistical accuracy.


As before, you can find my headphone frequency response measurements on VSG.squig.link along with all the earphone measurements. Scroll to the bottom and choose different targets there, including two from Harman Kardon developed after years of R&D. The Harman 2018 over-ear target in particular, is a reference curve many headphone makers aim for now, but I find it too bass-boosted. As such, I am opting for the Harman 2018 curve with the bass target from the Harman 2013 curve, which is what is referred to as the "Harman Combined" target. Before we get talking about the sound signature of the Aeon Closed X, I want to briefly talk about the measurements themselves and the channel balance achieved here. Given the nature of the fit/seal here on my artificial ears setup, the upper mids leading to the pinna gain are more pronounced in person than they come off here. This means that the 600 Hz-5 kHz measurements aren't the most accurate representation above—especially when we consider the part where this Harman-derived target is from one particular GRAS rig used by the Harman researchers, and mine isn't a wholly-compliant GRAS setup, let alone that exact one. The takeaway here is that the channel balance is actually far better than it seems here based on the graphs alone. Indeed, I appreciate the driver matching done by DCA to where this is one of the least expensive headphones with this level of consistency I've tested to date.

Second, and more importantly, anyone considering or even having previously purchased these headphones should first try listening to them after removing the pre-installed 1-notch white felt tuning materials. Indeed, I dare say that even the least dampening black foam simply has too much of a compromise here to where I even classified the default, and best, configuration of the Aeon Closed X to be when you have none of them installed. The drivers already have dampening paper as we saw before and all the other add-ons aim to do is tame the treble response further in increasing order of effectiveness. While it may seem like a good idea to have a warmer or brighter sounding set depending on your preference, unfortunately the sound comes off audibly muffled. This is felt across the board, on a set that isn't the most dynamic to begin with!

Indeed, it's hard to describe the Aeon Closed X if you haven't listened to it yourself. This is a set that is tuned quite well overall and makes for one of the more balanced closed-back experiences too. The set is certainly not slammy or punchy in the bass and ends up more my preference, allowing you to appreciate leading and trailing ends of tones. Electronic music with uniformly loud beats will be good here and you will notice the relatively softer dynamics instantly whenever there's a track with different tones at different volumes being played. It can be hard to appreciate drum ensembles, for example. I can only wonder if DCA could have gone with even lighter dampening on the drivers, if at all.

But on the plus side you do get a cozy and warm tonality in the mids that works well for vocals. Add to this the comfortable fit I had, and it was easy to chill out to lo-fi beats and imagine yourself as that very character having these over the head while studying/working. Forward-facing vocals combined with decent imaging and a surprisingly wide soundstage makes for a set that isn't the most technically competent or resolving, and yet might be my favorite closed-back so far for general media consumption. Indeed, If this was easier to drive, I'd have certainly thought about taking it along for the ride before the Focal Bathys took over that use case. As you get to the upper mids and treble proper, you will start to notice the trailing tones now come off softer than the leading ones, to where there's an unevenness to the attack and speed which planar sets are expected to have. Indeed, the relatively clean sound before combined with decent instrument separation now feels almost lost to where I can't recommend this for analytical orchestral music renditions. It still does the job well, especially given the overall good tonality, for relaxing music again in the form of acoustic jazz, R&B, and even simpler classical music.


I don't have a lot of other closed-back sets here in the price range the Aeon Closed X operates in. As it turns out, the two seen above are also planar magnetic sets in the form of the Edifier STAX SPIRIT S3 Bluetooth/wired set with active DSP, as well as the more directly-comparable Monoprice Monolith M1070C. These both cost slightly less and have different features too, with the Monoprice set also offering another set of pads with a distinct tonality, and yet neither come close to the overall comfort and balanced tonality of the Aeon Closed X. The Edifier set relies on DSP to get you there to an extent and does have EQ presets but no custom EQ support to negate that benefit slightly. Indeed, I'd also say that the Aeon Closed X does bass and mids, and vocals + most instruments, better than the STAX SPIRIT S3 too. The Monolith M1070C is interesting in that I do think it's more resolving than the Aeon Closed X but goes with a mild V-shaped tonality bordering on the brighter side. Those who are fans of the DCA house sound and the use of dampening materials to curb the treble response will not be fans of the Monolith M1070C anyway, and that's before I mention the vast disparity in weight and comfort between the two. I'd certainly recommend the Edifier for its more versatile use, but the Aeon Closed X still takes the win for those simply wanting to chill out at a desk. I'll also mention that the HIFIMAN HE-R9 is being tested as we speak, but that's another set which no one would justifiably claim as balanced. It's a bass-heavy set that ends up muddy most of the way to be more like a premium Beats headset from a few years ago and once again appeals to a whole different market, if at all.