Sound Analysis.

Drivability – Aeon Open X and Closed X have an impedance of 13Ω and 12.5Ω respectively and are extremely easy to drive from even the SE outputs of DAPs, smartphones and laptops. Though I’d recommend using a nice source to get the best performance out of both headphones.

Aeon Open X.

Note – I prefer both headphones without filters installed as they otherwise dull their overall performance in my opinion. The whole Sound Analysis as well as the Comparisons were written without the filters installed.

Summary – Open X is a fun tuned, fuller bodied presentation with a mid-bass boost and lesser sub-bass presence in comparison, around 5dB north of neutral boost in the 250-500Hz of lower-midrange which adds extra fatness and body to instruments but also some bloom, fairly clean and neutral 500-1kHz, forward upper-midrange with around 8-9dB of ear gain, fairly neutral lower and airy upper-treble presentation. The mid-bass and lower-midrange fullness take it away from reference accuracy and makes for a presentation that has a bit of veil but in turn also make for an easy laid back listen.

Let’s dig in deeper…

Bass – Open X focusses on a 5db mid-bass boost for extra punch over sub-bass rumble. It being an open-back design, the sub-bass reach isn’t the best and I can perceive a slight roll-off, primarily when comparing it to the mid-bass boost. The mid-bass oriented signature adds in boom, which may and may not be a good thing depending on your preferences. Reference heads would surely like to see this region cleaner and neutral but it does make for a signature than you can listen to at slightly loud levels for some fun with it ever coming across as intrusive. I personally would’ve like this region to be more neutral as the rest of the region, 500Hz and above, is extremely well tuned with a very clean and reference approach.

Midrange – Open X has added warmth because of the boosted mid-bass and 250-500Hz region of lower-midrange. This makes it a nice warm headphone that fans of fuller midrange will really like but also adds a bit of veil and bloom to an otherwise very well done signature. This fuller instrument body can be seen as addition of some romantic musical flavour for a nice and easy laid back listen but reference heads will take issue as it makes mixes sound slightly muddy and not as clean/neutral. The upper-midrange is quite well done otherwise. It has around 8-9db of ear gain which makes for a very nice and well defined forward definition of instruments. For me, a reference head, a wide EQ cut in the 60-500Hz range starts bringing Open X to perfection.

Treble – Open X’s lower-treble is extremely well done. It is very neutral and clean, which is even more appreciable if you turn the mid-bass and lower-midrange down a bit. Upper-treble is slightly airier than neutral with an airy boost around 16kHz, with very good extension till 20kHz.

Technical performance – Even with the warm-ish sound signature, Open X has impressive technical performance for the asking price. The boosted 60-500Hz does take away from absolutely good imaging and the soundstage it is capable of producing but it still has a well rounded soundstage, which is very slightly on the intimate side depth wise because of boosted mid-bass and fuller lower-midrange presentation. Open X isn’t the benchmark in detail retrieval in its price range but is quite good for its warm sound signature and shines MUCH better with EQ. It otherwise has good left to right separation with good layering and space between instruments. More about its performance with good EQ later in the review.

Aeon Closed X.

Note – I prefer both headphones without filters installed as they otherwise dull their overall performance in my opinion. The whole Sound Analysis as well as the Comparisons were written without the filters installed.

Summary – Aeon Closed X is a neutral-bright headphone and is better tuned than Open X in my opinion. Closed X has very good sub-bass reach and rumble, around a 3dB boost in the mid-bass around 100Hz, a slight dip around 200Hz, fairly neutral lower-midrange with very slight emphasis around 1.5kHz, forward upper-midrange with around 8dB ear gain, slightly warmer lower-treble and a fairly north of neutral airy upper-treble boost which lends it some brightness as well as a good sense of airiness and spaciousness. What is highly impressive in Closed X is that it is a closed-back with a very nice and spacious soundstage with excellent technical performance, that beats a lot of open-backs in its price segment.

Let’s dig in deeper…

Bass – Closed X has really good sub-bass extension down low and a slight bump in mid-bass around 100Hz which balances the upper-end airiness really well. The bass presentation is very clean, with a bit more oomph than neutral because of the boosted mid-bass. The bass is fast and is very well separated in the centre.

Midrange – The lower-midrange is very clean and ‘almost’ perfectly neutral. The upper-midrange has around 8db of ear which enables a very nice forward presentation of instruments. I would’ve loved a dB or two more of ear gain but this is still very well executed. Both vocals and instruments are presented with very good midrange tonality, though there is a touch of thinness because of boosted upper-treble.

Treble – Lower-treble is slightly warmer than neutral. I would’ve liked a bit more gain in the 6-10kHz region because of me being a sucker for absolute accuracy but most people won’t notice it as warm because the upper-treble is boosted significantly above neutral and makes up for the warmth in the 6-10kHz region. As a result, Closed X actually ends up sounding a neutral bright headphone. It would’ve been great if the DROP + Dan Clark could’ve tamed the upper-treble a bit because the 16-17kHz boost are almost 13-14 dB above a reference target curve like the Harman target. So, a bit more lower-treble and lesser upper-treble would’ve been perfect but that’s where EQ comes in and fans of headphones should get into the world EQ-ing too because it can greatly enhance one’s experience. Headphones are not as easy to tune as IEMs and EQ-ing really works wonders most times.

Technical performance – Closed X has exceptionally good technical performance for a closed-back of its price range. In fact, I’ll go as far as saying that it is the best at its price. It has excellent left to right separation, depth layering and imaging. It has a proper soundstage for a closed-back and actually stages like open-backs of its price range. It has really good resolution and depth layering for its price too – makes it quite easy to focus on reverb trails disappearing into the background.

Open X vs Closed X.

In a way they are tuned closely but some of their quirks make them very different sounding headphones, targeted at very different kind of people. Closed X is a neutral-bright headphone whereas Open X is a fuller bodied, slightly warm sounding headphone. Closed X has better low-end extension with better rumble and a small mid-bass boost around 100Hz that adds in a bit of extra punch to bass. Open X on the other hand has a slight sub-bass roll-off and a boost in the 60 to 500 Hertz region which boosts the mid-bass as well as instrument body and results in a much north of neutral, fuller bodied signature. It doesn’t just add in a lot of warmth but also a bit of veil and boom which takes Open X away from what could’ve been a very well done reference signature. Besides this, both the headphones have a very neutral lower-midrange post 500Hz and a nice, forward upper-midrange with around 8dB of ear gain. Open X has slightly better, more neutral lower-treble tuning, where Closed X is warmer. Both have a very airy upper treble tuning but because Closed X does not have the added warmth in the lower-midrange and ends up sounding brighter than the Open X as a result. In terms of technical performance, Closed X has a more open, airy and spacious sounding soundstage with better left to right separation and a better separated center image. On the other hand, Open X’s soundstage sounds slightly intimate with the stage depth not going as deep as Closed X’s. Closed X’s soundstage really has impressive depth in comparison along with impressive width for a closed-back. Closed X because of its brighter treble tuning, has better micro-detail retrieval as well as better layering and separation between instruments.

Performance with Corrective EQ.

If you’re a fan of headphones and still haven’t gotten into the world of EQ, I highly recommend that you do because it can add wonders and take the performance to the next level, something you can’t do as significantly with source pairing or otherwise. If you’ve never EQ’d before or don’t know where to start from, you can just start with using AutoEQ presets in Soundsource or Wavelet and take it from there. AutoEQ EQs the headphone to the Harman target and you’ll see a substantial improvement in tonality right away.

In the Aeon Open X, just EQ-ing out 60-500Hz by around 4-5dB, adding a bit of sub-bass below 60Hz and taming of the 16.5kHz upper-treble peak leads to it sounding much more accurate and more in line with the Harman target because the rest of region are very well tuned. You’ll see the technical performance coming across much better because the Open X is a very capable technically but the bloom because of the boosted 60-500Hz overpowers it and doesn’t let it shine as nicely.

In the Aeon Closed X, EQ-ing down the 100Hz mid-bass boost by around 3dB, filling in the notch around 200 Hz by 2dB, adding around 2dB of upper midrange in the 1.5-4kHz region, a bit more lower-treble in the 5-10kHz and EQ-ing down the upper-treble can lead to the Closed X sounding way more neutral, highly improving the tonality and making the technical performance shine even better.

For starters, you can use jaakkopasanen AutoEQ settings to EQ both headphones to the Harman target curve.

Aeon Open X Parametric EQ settings. 

You can use filters 1-5 or 1-10. Apply preamp of -3.4 dB or -3.7 dB, respectively.

#	Type	Fc (Hz)	Q	Gain (dB)
1	LowShelf	105	0.7	1.6
2	Peaking	155	0.78	-6.1
3	Peaking	2411	0.47	3.3
4	Peaking	5661	4.57	-3.2
5	Peaking	9415	2.96	2.1
6	Peaking	263	2.53	-0.6
7	Peaking	430	2.13	0.9
8	Peaking	759	3.5	-0.8
9	Peaking	3185	3.98	0.6
10	HighShelf	10000	0.7	-3.7

Aeon Closed X Parametric EQ settings. 

You can use filters 1-5 or 1-10. Apply preamp of -4.5 dB or -4.5 dB, respectively.

#	Type	Fc (Hz)	Q	Gain (dB)
1	LowShelf	105	0.7	-1.2
2	Peaking	106	1.06	-2.6
3	Peaking	186	2.38	1.4
4	Peaking	303	0.95	-1.9
5	Peaking	2130	2.4	4.4
6	Peaking	1065	4.45	1.2
7	Peaking	5610	5.95	-2.9
8	Peaking	6703	5.88	2.1
9	Peaking	9514	1.97	3.9
10	HighShelf	10000	0.7	-6.5

Comparisons with other headphones.

There are way more well tuned audiophile grade open-backs than closed back headphones. Closed back headphones are more difficult to tune and get right, which is very visible with the scarcity of extremely well tuned closed-backs in the market. Since Aeon Closed X has an excellent soundstage for a closed-back headphone and is very well tuned, I’m going to compare it to some of the best tuned popular headphones around $500 mark, regardless of them being an open or closed back design.

Closed-Backs – Aeon Closed X vs AKG K371.

There is no competition here to be honest. Closed X destroys the K371 left, right and centre in every aspect! Closed X has a WAY more comforatble fit which is actually a proper over ear design and where one’s ears don’t touch the driver assembly. K371 isn’t and the fit can

K371 can be seen as conforming to the Harman target slightly better but man does the Closed X beat it in every aspect otherwise. First of all Closed X as a closed back has a proper soundstage. K371 sounds like having no soundstage in comparison. Closed X has much better left to right separation and a clearer, better isolated centre image, better imaging, better depth layering as well as better imaging. To a lot of people K371 can come off a bit dark up top, which is why a lot of people preferred the K361 instead. Closed X has better bass performance that not only has better resolution and separation but also has a more accurate, quicker transient presentation. Both have really good midrange presentation but I’ll give it to Closed X for having better and more even upper-midrange presentation. K371 has slightly better lower-treble quantity but Closed just aces the upper-end airiness which greatly contributes to Closed X’s open, airy and spacious sounding soundstage as well as better micro-detail retrieval and the overall separation, especially relaying the space between each instrument.

Sennheiser HD6XX.

vs Aeon Closed X – Closed X extends very well till 20Hz down low whereas HD6XX has a sub-bass roll. Both have a slight mid-bass emphasis but Closed X’s boost is very slightly more. Both headphones have a very neutral and clean lower-midrange but HD6XX has a slightly more forward an upper-midrange, with around 2dB more of ear gain. Both headphones are slightly warmer in lower-treble but Closed X is much airier in upper-treble. Closed X completely beats the HD6XX in technical performance with a much bigger soundstage, better imaging, better left to right separation as well as micro-detail retrieval.

vs Aeon Open X – Quickly, HD6XX has better and more neutral tonality but the Open X has much better technical performance. Let’s go into more detail. In term of fit, even though HD6XX Both have a sub-bass roll-off but Open X has it lesser and has slightly better extension down low. Hd6XX too has a slight 2dB mid-bass around 150Hz but Open X takes it to the next level and has a 5db boost in the region. HD6XX’s mid-bass boost already lent it slight bloom but that is exaggerated in the Open X more. Open X’s lower-midrange sound fuller because the mid-bass continues into the 250-500Hz and as a result instruments have extra fuller than neutral instrument body added in. HD6XX sounds more neutral in the region. HD6XX has the more accurate upper-midrange too with 2dB more ear gain than Open X. Open X’s midrange though has much more resolution and better layering but more on that later. HD6XX has slightly warmer than neutral lower-treble where Open X is more accurate. Both headphones have an airy peak around 15-18kHz but Open X is airier in the region and that helps lend it a very slightly airier tonality than HD6XX. Where Open X completely beats the HD6XX is technical performance. Open X has WAY better left to right separation, better imaging, a better isolated centre image, better depth layering as well as overall micro-detail retrieval. This shines even better when you calibrate both headphones to the same reference target, something like the Harman Target. With EQ and corrected tonal issues, Open X shows it superiority even more and comes.

Hifiman Sundara 2020.

vs Aeon Closed X – Even though Sundara has quite a comfortable fit, I actually prefer the fit and comfort of Closed and Open X much more. Even the build quality of both the DCA headphones is MUCH better than HifiMan Sundara’s. Sundara has a very neutral signature, quite like the HD6XX but with better treble extension. Closed X on the other hand tries to follow the Harman Target. Closed X has much better low end extension till 20Hz whereas Sundara has a slight roll-off below 50Hz. Otherwise, Sundara has a very neutral bass presentation otherwise whereas Closed X has boost in mid-bass around 100Hz and a slight cut around 200Hz. Both have a fairly neutral midrange but Sundara’s upper-midrange has slightly more ear gain and sounds a bit more forward as a result. Closed X’s ear gain is very slightly lesser by around 2dB. Closed X has slightly warmer lower-treble but much airirer upper-treble than Sundara in comparison. Both have really good performance but Closed X wins in this department with a slightly deeper soundstage, better left to right separation and imaging as well as better depth layering. It being a closed-back can be an added advantage for people who’d like to have a headphone to use in noisy places with some privacy.

vs Aeon Open X – Sundara is a more neutral, reference sound headphones whereas Open X has a fuller bodied presentation because of boosts in both mid-bass and 250-500Hz of lower-midrange. Open X has very slightly better reach down low though both headphones aren’t the best at sub-bass extension. Sundara has a more forward upper-midrange because of about 2dB more of ear gain in the region. Sundara is very slightly brighter in lower-treble and mid-treble but Open X is airier in upper-treble. Open X has slightly wider soundstage boundary ends but otherwise a more intimate soundstage depth wise, primarily because of a fuller bodied presentation. Open X has slightly better left to right separation but otherwise both headphones perform similarly in terms of raw detail retrieval. Sundara can come off as having better micro-detail retrieval because of its relatively brighter signature.

Focal Elex.

vs Aeon Closed X – There is one thing that Focals are tough to beat at and that is dynamic punch. The sheer amount of punch the Elex has is seen from the get go in an A/B comparison between these two headphones. Elex is a more neutral, slightly warmer sounding headphone whereas Closed X is more a neutral-bright, much more open and airy sounding headphone. Elex has better sub-bass rumble and punch. Both headphones are fairly neutral in their lower-midrange presentation and are similarly forward in their upper-midrange tuning. Elex is more neutral in lower-treble but Closed X in much north of neutral airier up to, which is responsible for its leaner tonality too. In my opinion, when it comes to stock signatures Elex has better tonality overall because of a more neutral signature whereas Closed X is more exciting and energetic because of its airy upper-treble tuning. But it’s the Closed X that has better technical performance out of the two with a cleaner, more open and airier soundstage, better left to right separation and better micro-detail retrieval. Elex is no slouch though and is more dynamic, has better imaging and sense of instrument realism.

vs Aeon Open X – Right away, Elex comes off as the more neutral, natural and more accurate sounding headphone in comparison. This is primarily because of the big wide boost the Open X has from 60-500Hz. It results in north of neutral mid-bass punch as well as fuller body, which takes it away from an accurate reference tuning. Elex has better sub-bass rumble and even though Open X has the mid-bass boost, Elex has more dynamic punch out of the two. It’s just a thing Focals are really good at. Post 500Hz, both are quite well tuned headphones with a forward upper-midrange and neutral lower-treble tuning but Open X is much airier post 15kHz. Yet, it’s the Elex that comes across cleaner because of its more accurate and neutral tuning. Elex has a cleaner and slightly more open sounding soundstage with better imaging whereas Open X’s soundstage’s depth sounds more intimate because of the boosted mid-bass and extra lower-midrange fullness. Both have good left to right separation but Elex has a better separated centre image. Elex also has slight better micro-detail retrieval but that could be because of its more neutral tuning sounding cleaner and clearer in comparison.

Conclusion.

This was one big review to finish but I had a really good time taking both Closed X and Open X through the paces. Both have one of the best headphone fit designs in the world, where their earcups are made to the shape of an ear and have very comfortable earpads with good padding and depth – which make them one of easiest headphones for long sessions. Both are headphones targeted at different audiences – Closed X for fans of neutral-bright reference-ish tuning and Open X for fans of fuller bodied, warm signatures.  They both have really good technical performance for their price segments, especially the Closed X, which is one of the best tuned, VFM closed-back headphones you can get in the market today! If I had to choose one between them based on their stock signatures, I’d go with the Closed X myself. EQ adds on greatly to both headphones, especially the Open X, which sounds really good with a bit of sub-bass added in and the 60-500Hz wideband boost EQ’d down as the rest of the FR is very well tuned. All in all, I can recommend the Closed X as a must try headphone for everyone, especially people looking for close to reference tuning in a closed-back and the Open X for fans of fuller bodied signatures. Give ’em both a shot if you get the chance!

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Gear used for testing and review.

• Desktop setup – Universal Audio Apollo + DROP THX AAA 789 Amp
• DAPs – iBasso DX240 | Shanling M6 Ultra | Lotoo PAW6000
• Phone – OnePlus 7 Pro + HiBy FC4 / iBasso DC03 Pro / iBasso DC05

Artists I like and listen to.

• Rock – Foo Fighters, Linkin Park, Switchfoot, Imagine Dragons, Daughtry, Green Day, MuteMath, X Ambassadors, Dave Matthews Band, Vertical Horizon, Our Lady Peace, Lifehouse, Fall Out Boy, Breaking Benjamin, Muse, ACDC, Audioslave, Rage Against the Machine, Biffy Clyro, I Am Giant, Normandie, Paramore, Slash & Guns N Roses, 3 Doors Down.
• Pop Rock – John Mayer, Coldplay, Paul McCartney, James Bay, Hunter Hayes, Niall Horan, Keith Urban, The Bros Landreth, Bryan Adams.
• Progressive Rock/Metal – Porcupine Tree/Steven Wilson, Karnivool, Tool, Dead Letter Circus, Periphery, Lamb of God.
• Pop/Soft Rock – Ed Sheeran, Adele, Taylor Swift, OneRepublic, The Script, Gavin James, Magic Man, Maroon 5, Bruno Mars, Charlie Puth, Dua Lipa, The Weeknd, Oasis, Panic! At the Disco, TwentyOne Pilots.
• EDM – Chainsmokers, Zedd.