General Information


Drop + Dan Clark Audio
Open-back headphones
Individually serialized
Drivers: V-Planar planar magnetic, matched +/- 1.5 dB 30 Hz–5 kHz
Efficiency: 94dB/mW
Impedance: 13 ohms
Headband material: NiTinol memory metal
Ear cup material: Plastic frame, genuine carbon fiber inserts
Earpad material: Japanese protein leather (removable)
Input connector: Hirose 4-pin
Cable: DUMMER 4-pin (3.5 mm) to ¼ in (6.35 mm) , 6'5" (2 m) long
Weight (without cable): 11.5 oz (326 g)
Made in San Diego, CA


Latest reviews

Pros: Spacious at times, driver is detailed, EQ may be sufficient for some
Cons: tonally imbalanced, bass is to forward and wet [excessive overemphasized harmonics], lacks dynamic contrast

Introducing the Dan Clark Audio X Drop Aeon Flow Open X , I'd like to start by thanking Drop for giving me the chance to review headphone. This is a Dan Clark Audio Aeon Flow Open tuned by the Drop Team, so it's a collaboration! Having not heard the original tho I can't say what they've changed. Price is at $499 via Drop. I did receive this just before launch on a temporary in home demo with the understanding that I share my thoughts of my own accord without any compensation. Moving forward tho I'll be shortening the Aeon Open X by Dan Clark Audio & Drop to just simply AFO-X.

Overall AFO-Xs build quality is consistent with what we've seen and come to expect from Dan Clark Audio. Even the packing is identical to the original AFO except for the labeling which identifies it as the Aeon Flow Open X Drop Collaboration with Dan Clark Audio.

Tuning pads are included with the White 1 Notch Filter pre-installed, best of all the original Mr.Speakers headphone carrying case is also included!

Sound Quality
Overall I find AFO-X to have a thicker tonality with a beautifully natural mid-range and lots of detail. However it's tonal balance is a bit off and with really any piece of music consisting of more than 2 instruments the overall coherency tends to break apart. I'll also add the pre-installed 1 notch White filters didn't add anything worthwhile to my ears as they only smoothed the top end and further proved a detriment to the already warm tonal balance.

So all of my listening was done without them.

For this review I choose to stick with the SMSL SP200 for it's transparent presentation and truly colorless amplification. Given how much personality and character headphone brings I found it performed best with a clean powerful amp. I did try a couple of Hybrid Tubes and each had more drawbacks than real worthwhile benefits. Namely they overemphasized problem area's with AFO-X's response and presentation.

All listening for this review was done offline with 16/44.1, 24/96 or 24/192 offline lossless recordings, track list is as follows

  • Hotel California - Eagles [Hell Freezes Over] (Simply Vinyl 180g Rip)
  • Guess I'm Doing Fine - Beck [Sea Change] (MoFi UDCD 780)
  • Good Man - Ne Yo [Good Man] (Motown Records Deluxe Edition)
  • Drum Kit Dynamic Range Uncompressed: Test - Dr. Chesky [The Ultimate Headphone Demonstration Disc]
  • 7: Gigue - Eugene Drucker [J.S Bach - Sonata & Partitas for Solo Violin]
I don't have a definite opinion on "burn in" however I respect those of you that do and I do run about 5 days of 24/7 pink noise before I do any listening. I also like to spend a full day just exploring music before I start comparisons and any critical listening with the playlist listed above.

Synthesized low frequencies such as what we enjoy in modern Pop, RnB and Hip Hop are presented with both speed an authority. However I found that with both natural acoustic instruments and even electric stringed instruments the overall presentation was stuffy, sluggish and ill defined. There was a serious lack of definition and an overabundance harmonic overtones that resulted in a some what flat or smashed/squashed tonality.

So the bass lines in songs like the Hotel California and Beck's "Guess I'm Doing Fine" has insufficient texture or definition, how ever the powerful deep kicks on Ne Yo's "Good Man" had genuine speed and authority. An getting back to this idea of simplified less complicated and populated mixs, I did enjoy a few simply drumming tracks with AFO-X.

The star of the show and often the soul music are the beloved mid-range frequencies. This is where AFO-X really excelled, bring both a sense of warm naturalness but with insane speed, definition and presence. I was time and time again impressed with how accurately AFO-X presented the mid-range, even given the poor overall tonal balance and kinda flat often stuffy presentation I never found my self unable to enjoy and appreciate AFO-Xs beautiful mid range!

Overall I found AFO-X to be a little hot and splashy up top, this often bleed into the upper mids resulting in some emphasis on breathing and mouthy noise from singers in addition to an oddly dry or weirdly aggressive presentation. I'd be lying if I didn't admit to enjoying this presentation with a few specific tracks, but for long term use I wasn't really too impressed.

Detail and Dynamics
The mid-range was in particular exceptionally detailed with AFO-X, almost shockingly so, how ever problems with an excess in the lows often de-emphasized some of this detail. Which made it detail difficult to perceive but never impossible to find. Still as detailed as it is the overall dynamics or presentation of quite and loud sounds overlapping and within the same space was extremely damped or muted. Sadly AFO-Xs does not do much to truthfully present the full dynamic range of even well recorded and mastered passages of music.

Staging & Image
Despite everything I was surprised at how precise the image AFO-X presented was, movement both vertically and lateral was easily discernible. However, there was still this unpleasant boxy sound to it all. Not to mention if there was a kick drum in the mix it's sound alone ate up around half the audible space presented. Still my critical listening tracks are split between a Drum & Bell, just Vocals and a "Shaker Test" and while I respect it's technical performance within these given Test Tracks that technical prowess does not translate well beyond very simple straight forward compositions and music.

AFO-X vs ESP 95X

I'll start by admitting the overall tuning goals here are different, AFO-X is characterized by it's engaging warmth and body where as the Koss 95X is more or less dis-engaging or tuned to by far more linear and transparent. That as a listener I find myself more engaged while listening when my system as a whole has less emphasize. 95X certainly embodies that mindset tho quite a few who have heard it don't quite agree and find it "boring." That said;

Compared to AFO-X, I found 95Xs presentation of Mid-Range Frequencies to be;
  • Not as rich or sweet
  • Equally as detailed
  • Resolved a little more depth within a given stage/acoustic space
  • Never stuffy
    • There where times while listening with AFO-X that singers in particular sounded incredibly boxy. 95X had NONE of this boxy or stuffy sound
Compared to AFO-X, I found 95Xs presentation of Low Frequencies to be;
  • Recessed
  • More vividly detailed and textured
    • AFO-X simply lacks detail, resolve and texture in the lows for many stringed instruments
Compared to AFO-X, I found 95Xs presentation of High Frequencies to be;
  • Not as forward or in your face
  • Better extension or more balanced/resolving envelope
    • Clean, Clear and well defined leading edges and decay from that initial attack
    • Vivid sustain and exceptional clarity when presenting the trailing edge of high frequencies
  • Drier
    • As in not as "wet" sounding
Overall technically and for my personal tastes I found 95X to be superior overall, the only Genre where AFO-X was more enjoyable was EDM given it's fuller and more prominent sub bass response.


With these two there are tonal differences but I find the Mid Range to be the strength of each with each bringing a richer or wetter presentation to mid range frequencies.

I am happy to admit that technically the HE 4XX doesn't quite compete with AFO-X. AFO-X has better resolve and provides a more spacious and precise image. Tho I do prefer the overall tonality of HE 4XX more so, so I perceive a lot more detail with HE 4XX where as I do have to listen for it on AFO-X. An indeed when I'm listening more critically it is apparent that AFO-X is technically better.

Compared to AFO-X, I found HE 4XXs presentation of Low Frequencies to be;
  • A touch emphasized
    • But not as boomy
  • Better tonality
    • With Texture proving easier to perceive
Compared to AFO-X, I found 95Xs presentation of Mid-Range Frequencies to be;
  • Not Quite as Tactile
  • More even or correct timbre without being drier or lacking warmth/wetness
  • Not quite as detailed or resolving
Compared to AFO-X, I found 95Xs presentation of High Frequencies to be;
  • Touch more forward
  • Not quite as detailed
Staging tho is a bit... flat compared to AFO-X, HE 4XX often lacks a real sense of defined space. Things that are in front can come across as above, where as AFO-X does a better job at preserving and presenting a more three dimensional sense of space. The Chesky Binarual Disc is a nice listen for this kind of presentation and thankfully most of the time with actual Music AFO-X translates this precision.

AFO-X vs LCD 2 Classic

Now these two headphones do share a some what similar warm thick presentation. Both even share a similar price and topology!

Compared to AFO-X, I found LCD 2Cs presentation of Low Frequencies to be;
  • Weighty when needed
    • Never too excessive or boomy
  • Thicker with Synth Basslines
  • More resolving,
    • With better detail and power!
So just better, while AFO-X presented Synth Basslines with more speed and didn't quite capture the fullness or warm tone that ole school Dub Step often has. Again the Dub being in reference to Dub Music an offshoot of Reggae which saw a heavy use of round wound stung bass guitars which often had a warm cozy bass line. AFO-X was sometimes too punchy so kinda off to my ears. Ironically tho with actual Bass Guitars AFO-X consistently lacked punch comparatively and sounded TOO warm and cozy...

Compared to AFO-X, I found LCD 2Cs presentation of Mid-Range Frequencies to be;
  • Slightly recessed
  • Not as rich nor as full
  • Lacking a little texture/edge
  • Presented with better depth relative to the acoustic space
Compared to AFO-X, I found LCD 2Cs presentation of High Frequencies to be;
  • Slightly recessed
  • Equivalent extension and detail
Now what I like about LCD 2C is it takes quite nicely to amplification like the Schiit Lyr 3, and such a pairing maintains a lot of LCD 2C's strong points but add's a little richness without a massive loss in texture or edge. Where as with AFO-X anything outside of a clean solid state will only further detriment it!

AFO-X vs HD 600

Simply put I found HD 600 to be simply better across the board, while not as spacious in terms of width the image it presented was more cohesive with better precision. HD 600 had far more detail, transient response is incredibly vivid and dynamic contrast was vastly improved.

Tonally even tho HD 600 is rolled off it presented more detail and texture in the low frequencies, relative to about 40 hrz. There was and is just a sense of clarity, precision and naturalness with HD 600 that is lacking in AFO-X.

Compared to AFO-X, I found HD 600 presentation of Low Frequencies to be;
  • More textured an detailed within limits of response
  • Vivid
  • Rolled off
    • Only obvious and problematic with deeper synth bass lines
I'd say the only genre of music where AFO-X excels and HD 600 falls short is EDM that feature a lot of heavy deep bass lines.

Compared to AFO-X, I found HD 600 presentation of Mid-Range Frequencies to be;
  • Lively without a lack of naturalness
    • Vocals have a more defined body and place within the recorded space
  • Textured with a clean envelope
    • Slight upper mid-range forwardness adds presence and texture without being detrimental
  • Slightly drier
    • Or lacking added warmth/wetness
Compared to AFO-X, I found HD 600 presentation of High Frequencies to be;
  • Well extended without added emphasis
Sadly the only thing preventing HD 600 from being hands down a better buy is it's lack of low bass extension as the roll off can really be a detriment to some genres of music. However with all acoustic music and anything above about 40 Hz I do feel HD 600 is better.

An I'll also add that HD 6XX/650 will likely compare similarly except it'll have that slightly wetter/richer mid range and improved low bass response.

AFO-X vs Mr. Speakers and Dan Clark Audio Family of Cans

Right off the bat I'll start by saying I don't feel AFO-X is in even the same league as the new Dan Clark Audio Aeon 2 Closed. A2C has a tiny smidge of warmth and fullness but provides a significantly cleaner, more nuanced and resolved presentation. It's both technically and tonally better in every regard to my ears.

Original AFC and Ether CX prove to be better comparisons, with CX proving to be subjectively about as Open as AFO-X to my ears. While AFO-X has a nice open airy sound at times, it's overly forward ill-defined bass stifles any perception of "spaciousness."

Where as with CX there isn't quite the same openness but there's also not this constant stifling boxy low end either. I also felt CX was equally as detailed in the mid-range with better top and bottom end resolve and more or less equivalent dynamics. An while CX is not as rich as AFO-X it isn't too lean by comparison to my ears.

Compared to AFO-X, I found Ether CX's presentation of Low Frequencies to be;
  • Not as forward or powerful
  • More detailed & textured
  • Cleaner audible extension
  • Not "flat" sounding
Compared to AFO-X, I found Ether CX's presentation of Mid-Range Frequencies to be;
  • Still rich but more balanced
    • Not as "thick" or "syrupy"
  • Without audible stuffiness
    • does NOT sound like it's coming from within a box or small cramp space
  • More detailed
Compared to AFO-X, I found Ether CX's presentation of High Frequencies to be;
  • Slightly recessed but with cleaner more audible extension
  • Not as wet or splashy
AFC on the other hand is quite different in terms of presentation from AFO-X. I felt AFC was never quite as "open" sounding as AFO-X could be however, AFC had better precision and cohesion within the audible space.

Compared to AFO-X, I found AFC's presentation of Low Frequencies to be;
  • Recessed
  • Cleaner sense of power and extension
  • More detailed/textured
  • Not flat sounding
Compared to AFO-X, I found AFC's presentation of Mid-Range Frequencies to be;
  • Noticeably drier
  • Presented with a more vivid vibrato
    • For both vocalists and horns especially
  • More detailed
Compared to AFO-X, I found AFC's presentation of High Frequencies to be;
  • Equally extended
  • Similarly wet or splashy
  • Not as open or airy
Overall I still prefer AFC at this given price point despite it being a closed back.

The big question tho is how does AFO-X compare to a my personal favorite headphone with a similar presentation?

Let's start with it's strengths, compared to my PreFazor LCD 2.2 AFO-X is;
  • More open or spacious with regards to the "width" or the perceived space
    • Only when there isn't any low bass spectra in the mix
      • So what with a third of my music...
  • A bit more natural with Spoken word and some vocals
    • Assuming the vocalist doesn't have a deep voice
    • Watching a few TV shows with AFO-X wasn't bad, more often than not vocals sounded more correct with AFO-X than PreFazor LCD 2.2
An that's pretty much about it, AFO-X is and can be spacious but it's loose ill defined and overly forward yet still flat bass really kills the perception of "space" and air for me.

Technically my 2012 PreFazor LCD 2.2 is;
  • More detailed
    • Easier to hear and discern transits
    • Presented a cleaner envelope
  • Sharper more distinct dynamics
    • Both Macro and Micro
An tonally;
  • Even more power in the lows without any loss in detail/texture or definition
  • Thick rich mid range with good presence and "bite"
  • Dark or recessed top end yet still presents a more natural sounding extension
Now oddly enough with vocal heavy Music PreFazor LCD 2.2 sounds fine, just spoken word like what we find on TV for some reason comes across a bit odd on it.

Granted, not every one will be able to find an equivalent sounding PreFazor LCD 2.2. Non the less, I just don't feel AFO-X really measures up to my personal standard for how an "organic" or "natural" tuned headphone should sound.

Again given it's many many flaws I can't quite say AFO-X gets my recommendation. It may have brought improvements over it's 1st gen counterpart but I don't feel it's competitive enough in today's market to merit my recommendation.


Comprehensive and interesting review.
For context, I bought the AFC last year, and enjoyed it so much, that I was regarding it as my 'find of the year'.
Then for Christmas I snapped up the 95X - I had been thinking about exploring a pair of electrostats for a while, and when Drop offered them at the EU warehouse closing down price of €290, it was a no brainer.
Only been using the 95X for a couple of weeks, but quickly started to think of them as my second 'find of the year'.
I expected the 95X to easily be the fastest, but surprisingly I am finding the AFC to be just as fast. The AFC seems just slightly better for the double bass, but the 95X seems to just provide slightly more space around percussion such as cymbals. Both are similarly enjoyable for listening to acoustic jazz, but maybe the 95X edges ahead for recordings where there is space between the players on stage. In contrast I too find the AFC to be slightly better, when listening to music with a large proportion of electronic instruments such as synths.

However the AFO-X had set me thinking, about whether I would find it kept the good aspects of the AFC, but added the extra space between instruments provided by the 95X.
Your review has provided the evidence/answers for me.
Enjoy the AFC and 95X for the present, but consider the A2O when it becomes available in a couple of years.