Ollo Audio S5X

Unparalleled warranty, ownership experience and Serviceability at minimal cost.

Before we get to Sound Analysis, this is something I want to talk about and also give Ollo credit where it’s due for setting something like this up. S5X comes with a 5 year warranty, which is unparalleled in this industry. That just shows how confident Ollo are in their build and parts selection. Another thing that I think differentiates Ollo Audio from all the other headphone manufacturers around the world is that the whole headphone is designed in a way that you can open it up and service it at the comfort of your home within a couple of minutes. All the parts you’d need can be ordered from Ollo’s Spare Parts Store individually. The prices have risen from what they were for S4X but they are still very reasonably priced. A pair of S5X ear pads are €37.90 and a pair of matched S5X drivers are €69.90. They can however repair the headphone for you too if you’d like to send it to them and have them service or fix it up for you instead.

Sound Analysis.

Drivability – SSX are rated at 50Ω with a sensitivity of 108dB SPL@ 1kHz. It is fairly easy to drive through smartphones, laptops and SE output of DAPs, though needs a tiny bit more juice than other 30-40Ω rated closed-back headphones like AKG K371 (32Ω) and Audio Technica M50X (38Ω).

Ollo S5X RAW Measurement.

Ollo Audio S5X

Note – This is a highly smoothed graph.

Summary – S5X is tuned to be a reference headphone, where it does some things quite in line with existing approach to reference tuning and some not as much. S5X has a very neutral bass presentation and good linear sub-bass extension till 20Hz, which is one of the nicest I’ve seen in this price segment for an open-back. Where most open-backs in this segment have a minor sub-bass roll-off, the S5X doesn’t. It has a very neutral and linear lower-midrange but around 6dB of ear gain, which is on the recessed side of Harman as well as Diffuse Field target and takes it away from absolute reference accuracy. The overall treble balance is fairly neutral, if not very slightly on the warmer side of neutral but with good extension till 20kHz. Tonally, I see it as an improvement over the S4X with a cleaner and more linear bass presentation and better treble balance. If you already own the S4X, the first thing you’ll notice in the S5X right off the bat is the soundstage. S4X had a rather average soundstage but S5X improves that and stages much better in comparison.

Let’s dive in deeper…

Bass – S5X has a very nice neutral bass tuning with good linear extension down till 20Hz, which is one of the strong suits of S5X as an open-back since open-backs in this price range generally have a sub-bass roll-off below 40-50Hz. It’s clean and accurate, something reference head audiophiles and pro-mixing and mastering engineers would appreciate. The bass has good speed and good centre imaging – all combined make for a bass presentation that is a fair and accurate representation of the songs. S5X’s bass presentation is cleaner and extends better than HD6XX’s, which has a sub-bass roll-off and then a tiny boost in mid-bass that adds in slight veil in the signature. But on the other hand, it falls behind in bass precision, clarity and sheer resolution that HifiMan Sundara has.

Midrange – Lower-midrange is very neutral and linear, which helps keep the mixes sounding clean and also helps keep the instrument body and tonality of the drum shells and baritone vocals sounding correct. Upper-midrange on the other is slightly recessed as S5X has around 6dB of ear gain, where around 9-10dB is considered to be neutral and tonally accurate. This makes for a slightly laid back listen with no upper-midrange shout, which is good for limiting fatigue in long sessions and might be preferable to people who like ear gain on the easier side of neutral but it is one of my main gripes with S5X as this is the main thing that takes it away from accurate reference tonality and an accurate forward presentation and definition of instruments. 1-2dB lower than Harman or Diffuse Field would’ve been perfect for a slightly easy laid-back listen but 4dB lower gets a bit low in my opinion and majorly affects instrument tonal presentation and definition.

Treble – S5X’s treble balance is slightly on the warm side of neutral but the upper-treble extends fairly well till 20kHz. I would’ve liked a bit more lower-treble to bring the S5X absolutely in line with a reference accuracy and a bit more upper-treble air wouldn’t have hurt either and would’ve added greatly to technical performance too. Again, the warmth is welcome for long studio sessions that go on for hours as you need ears working in top form without fatigue creeping in quickly, which is where warmer headphones help. But S5X’s treble being on the warm side reduces its micro-detail retrieval ability and absolute tonal accuracy when compared to headphones like the HifiMan Sundara 2020 or the DROP x DCA Aeon Closed X. Sure, both those headphones are then slightly brighter than neutral in their mid-treble tuning, but they come across more resolving in an A/B test even when calibrated to match the same reference target curve. That resolving character of Sundara and Closed X actually helps them shine a light on the smallest of details when listening intensely or when working on mixes as an engineer. That is a character I’d personally prefer over a warmer than neutral treble tuning. But to be fair, S5X is no slouch and once you get used to its signature, I found it to be quite good for production work – especially when crafting the instrument tonality in a mix or when EQ-ing to make everything fit together.

Technical performance – S5X has a good soundstage with good imaging – a significant upgrade over the S4X and headphones like the HD6XX. The reason why Ollo market it as an ‘Immersive Mixing’ headphone is because it stages the best amongst their lineup of headphones, much better than their previous S4X. It especially has good depth and even better depth layering when compared to S4X or even the HD6XX. It has good left to right separation, imaging and micro-detail retrieval ability but there are a couple of headphones like Sundara and Elex that have even more competitive performance in this price segment, which we shall talk about in the Comparisons section below.

Ollo Audio S5X Solo D

Ollo’s compensation graph with Ollo Target.

This is a complaint I have with Ollo. Even though they’ve published an excellent Measurement Report October 2022 as a PDF that includes measurement of all their headphones, RAW and Compensated to their Ollo Target, along with some other popular models from Audio Technica, Austrian Audio, etc., it’s a bit disappointing that they didn’t let us know what their Ollo Target actually is.

The graph below shows the S5X’s FR compensated to their in-house Ollo Target. It would’ve been great if Ollo would’ve made their target curve public and shown us how it looks, like Harman, Etymotic and Moondrop did with their own target curves. Since reference is such a loose term these days and target curves like Diffuse Field, Free Field and Harman are quite different in the way they look and sound, it is easier if we can see the target curve to know the kind of signature a manufacturer is trying to target for their products, why and how it is different from the existing target curves and the kind of research that was done to arrive at such a target. Without this information, we cannot know if the target really is a good reference target or not. The thing is that any compensated graph can be made to look good by making a target that is really close to the headphone’s RAW graph. With so many good reference target curves out in the open and even more reviewer preference target curves available in the market, the fear of IP infringement goes out of the window and making a ‘good’ target curve public can actually bring the brand much more popularity (like Harman’s did). So, a company making reference products should make the community and industry aware of their target curve and the basis of the research they did to arrive at it – to keep everything transparent, free from doubt and in fact help and contribute in the advancement of research in the field.

Ollo Audio S5X Graph (Compensated)

Comparisons with some Reference tuned headphones.

I can tell you right off the bat that S5X is a better reference headphone than headphones like the Audio Technica M50X, Beyerdynamic DT770, DT-880 Pro and DT-1770 Pro, AKG K702 and K712, Austrian Audio HI-55 and HI-65 that are claimed to be reference/monitoring/mixing headphones but aren’t really as they’re either tuned too wonky or too bright. Even if you’re looking for a closed-back reference headphone, I’d in fact recommend looking at the DROP + DCA Aeon Closed X, AKG K361 or K371 instead.

Ollo S4X.

When it comes to fit, S5X has very slightly bigger and cushier ear pads and a better feeling head pad which result in a much more comfortable than the S4X. Even though S5X is no heavy headphone, the headpad distributes the weight of the ear cups much better. Design wise too, I personally like the S5X more. Even though S4X was no slouch and had a very nice raw industrial design, S5X is a step ahead in evolution. The first difference that you notice between the S5X and the S4X is that S5X has a much more open soundstage with wider width and deeper depth. S5X HAS a more even, more neutral bass to lower-midrange transition with better, more linear extension down low to 20Hz. S4X has a very slightly boosted bass presentation in comparison. S5X has a more even lower-treble balance as well as better upper-treble extension. It’s the S4X that has a slightly more accurate and better forward upper-midrange definition whereas S5X sounds slightly recessed in comparison but I’m talking 1-2dB difference here and there in the 1-5kHz region. When it comes to technical performance, S5X has better detail retrieval, better left to right separation, better depth layering resolution as well as better imaging with instruments sounding further apart and better spaced out because of a more open soundstage. Even though I would’ve liked slightly more ear gain; a bit more gain in upper-midrange, S5X easily comes off as the more superior headphone and a worth successor to the S4X.

Focal Elex.

The Focal Elex too is tuned as a reference headphone but there is a stark difference between how they sound. Elex’s build is as premium, if not more than S5X’s. Elex also has a way more comfortable fit in comparison, with earpads completely engulfing the ear and the clamp force being easier and more comfortable for long sessions. But where Ollo beats the Focal is their 5 years warranty and the modular-ish build that allows you to easily service the headphone at home. When it comes to sound, Focals have this unique ability to sound more dynamic and punchier than most headphones and Elex is no different. It has more to do with the amount of air they push than mere gain in the bass region because even the most neutrally tuned Clear and Elex that have a very linear bass tuning without a boost, sound as dynamic as other Focals. Elex has better extension down low with better sub-bass rumble as well as better mid-bass punch. Both have very clean, linear and neutral in lower-midrange but Elex has slightly more ear gain; a more accurately forward sounding upper-midrange. The S5X sounds very slightly recessed in comparison. Both headphones are slightly warm in lower-treble and have fairly similar upper-end extension but I hear Elex’s treble presentation being more natural and accurate to my ears. Elex has a slightly more open sounding soundstage as well as better depth layering and stronger imaging. Both are fairly resolving headphones but Elex has slightly stronger instrument definition owing to it having more accurate ear gain.

HifiMan Sundara 2020.

Sundara 2020 again is a reference headphone but with a planar magnetic driver, unlike the S5X which has a dynamic driver. Sundara was initially launched at $500 but can now be found selling around $300. There is absolutely no match in terms of build quality as the S5X is a much more premium and better built headphone. Sundara on the other hand is a much more comfortable headphone as its earpads completely engulf the ears with a fairly light clamp force. Coming to sound, S5X has better extension in sub-bass and extends properly till 20Hz whereas Sundara has a sub-bass roll-off around 50Hz. Both have a very neutral, linear and clean sounding lower-midrange but Sundara has better ear gain; more neutral and accurate sounding forward upper-midrange. Sundara is more neutral in the lower-treble region, slightly brighter in mid-treble region of 10-14kHz and airier post 16kHz. Both have a good soundstage for their asking price but Sundara has slightly wider boundaries. Sundara comes across more resolving of micro-details, majorly because of its brighter treble tuning but S5X is no slouch and does it fairly well for its own signature. Sundara has slightly better left to right separation and layering of instruments. When it comes to reliability, HifiMan has had infamous history of bad QC and their headphones not ageing as nicely. Ollo Audio on the other hand offer a 5 years warranty on the S5X along with a build that is not only more premium and better built but is also quite easy to take apart and service at home if ever required. So, if that’s a priority, S5X could be the better overall product but when it comes to a more accurate reference tuning, Sundara takes the cake.

Ollo Audio S5X + Lamp


There is no dearth of good reference headphones under $500. This is in fact one of the most competitive price segments when it comes to headphones but S5X holds its own and offers a good value proposition for its asking price of €449. It has a fairly neutral, well balanced signature. It does have its caveats, especially the slightly recessed ear gain and slightly warmer lower-treble when compared to reference targets like the Harman target and a technical performance that is bettered by headphones like the Focal Elex. But where it does better than most in its segment is build quality, reliability and warranty. With good light weight, Walnut wood earcups, well made metal headband, a head pad that distributes weight really well and fairly comfortable earpads – this is one of the better, if not the best crafted headphone at its asking price. Where it kills the competition is the unparalleled 5 year warranty and a modular build which gives you the ability to take it apart and service the headphone yourself at home. This really shows how confident the brand is in its product and the kind of no-BS ownership experience they want to provide their users, which is even more important in the professional world where one needs tools they can rely on at all times. IMO, Focal Elex and HifiMan Sundara do better when it comes to reference accuracy but S5X is quite close and with all its pros combined, it is a fairly easy headphone to recommend otherwise. Definitely check it out if you’re looking for a monitoring or mix-referencing headphone with a worry free ownership experience!

Gear used for testing and review.

  • DAPs – iBasso DX240 | Shanling M6 Ultra
  • Desktop Setup – Universal Audio Apollo with DROP THX AAA 789 Amp
  • Laptop – Apple Macbook Pro 15″
  • Phone – OnePlus 7 Pro

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.

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