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Ollo S4X Dynamic Headphones – Mix, Master & Listen

Ollo S4X Dynamic Headphones – Mix, Master & Listen

Who loves headphones? I surely do! This is why this website is named Audiophile-Heaven, and the headphone we’re reviewing today is not just for those who love music, but also for those who make music. For those hard workers who do their best so we can enjoy one of the purest forms of art. S4X from Ollo Audio costs about 400 USD / 400 Euro, so it will get compared to HIFIMAN Deva, Sivga P-II, iBasso SR-2, and Adam Audio SP-5. The pairings will include Singxer SDA-2, FiiO M11 PRO, and iBasso DX220 MAX



I had the chance to talk with Ollo Audio and their crew way more than I did with most other companies, so you could say that I know them in and out. The best part about Ollo Audio is their reliability. They are a company ready to stand behind their products, they are a company ready to love you and who really loves music. Most of their ideology is centered around producing instruments for music players and those who mix, master and record rather than appeal just to the Audiophile Crowd. I can say for sure that if you’re to have any issue with their headphones, they will help. The headphones are generally modular too, so they can simply send in a headband, driver or the component that is problematic, and you’ll replace it in less than a minute.

It should be noted that I have absolutely no affiliation with Ollo Audio, I am not receiving any incentive for this review or to sweeten things out. I’d like to thank Ollo Audio for providing the sample for this review. Every opinion expressed is mine and I stand by it, the purpose of this review is to help those interested in Ollo S4X Headphones find their next music companion. 


Product Link

You can purcahse Ollo S4X from their own website (Global) here: https://olloaudio.com/pages/s4x-reference-headphones



First things first, let’s get the packaging out of the way:

Ollo S4X has probably hands-down the worst package I’ve seen for a headphone in this price range. Really hard to put back and just plain cardboard, but that’s actually awesome! They make a big deal out of using recycled materials and being as environment-friendly as possible to help not just create music, but make this world a better place also. 

For this price point, the package is a bit disappointing in terms of contents too, most headphones tend to include spare pads, cables and carrying cases, but there’s nothing like this with S4X. Just the headphone, and a cable. The cable quality is pretty good though and should serve well, being easy to replace too if you’re a fan of aftermarket cables. 


Technical Specifications


Build Quality/Aesthetics/Fit/Comfort

Ever since I reviewed the Dan Clark Aeon Flow, I’ve been afraid of proprietary cables, but it looks like Ollo designed their S4X to have the cables easily replaceable. Not only that, but Ollo made sure they included a fairly good cable with their S4X, and good earpads too. 

The headphones are open-back and they are made to leak less than most open backs, and to isolate a bit more too. The comfort is generally good, but they are a bit small for my large ears. I would call the fit over-the-ear for most people, but be careful if you have really large ears. 

Driving factor is medium, they are somewhat hard to drive, but are very consistent across sources, sounding pretty much the same regardless of the source. I would recommend at least a FiiO K5PRO, or a Lotoo Paw S1 as the sources but better sources will give better dynamics and better punch. The detail levels and overall signature stays unchanged regardless of the source, and I appreciate that, as for a mixing / mastering headphone it is excellent. 

The headphones are made of wood, metal and dynamic drivers. This means that they are somewhat heavy, they feel very well build, robust and I would call them one of my top headphones. 


Youtube Video


Sound Quality

The overall sonic signature is forward, extremely detailed, clean, clear, slightly grainy, and pretty dynamic. The tonal balance is absolutely neutral, and the overall revealing abilities fairly outmatch the price you’re paying with S4x. The sound is generally a bit more characteristic of Planar Magnetic Headphones than Dynamics and really reminds me of Audeze LCD-MX4

The bass is really quick, linear, and not very warm. The whole sound is a bit thick in the mids, and has good substance, but there’s not a lot of emphasis on it. The amount of bass is good, but it is not overly much, and it only makes itself heard when it is intended to. If it wasn’t in the mix / master, the headphone won’t show you any bass. This is a good thing for mixing, mastering and making music, but they can be a bit boring and bland for listening. Metal sounds accurate, quick and detailed, Pop sounds really accurate, while hip-hop sounds like it would need a bit more bass. 

The midrange is somewhat forward, especially if you’re coming from colored or “fun” headphones. In reality, it is one of the most neutral midrange that I’ve heard, but this can be a bit odd at first. The ratio is the most rare one, the midrange being the most enhanced part of the sound, with the bass coming after, and the treble being the least emphasized. The mids are really clear and detailed, but they don’t sound crisp. Everything is a touch smooth, kinda like how Chord Mojo presents music. The dynamics are good, characteristic of a dynamic driver, but the midrange can present transients both a bit smooth, but also with a bit of grain, textures being a bit stronger than what I’m used to. The presentation emphasizes detail and clarity, and the mids are a bit thick too, so everything can be listened for many hours in a row, and Ollo S4X reveals mistakes in master and recording easily. 

The treble is the least interesting part of the sound, being fairly smooth and unenergetic. This is good if you’re working with music for many hours in a row, but it can be a bit bland and flat if you want a bit of sparkle. To be honest, I enjoy Ollo S4X the most at night, when I don’t have much energy left, and when I want to relax to some good music. Jazz music sounds the best, Classical is awesome too. Metal, rock and punk lacks that top end punch / edge, while pop sounds a bit too focused on voices for my general liking. 



The best comparisons I could find are with Sivga P-II, HIFIMAN Deva, and iBasso SR-2. There’s a ton of competition in this price range, and Ollo S4X is nicely aimed at a niche, the ones who do music production too. While writing this part, I also decided to add Ultrasone Signature Studio, which has the same sound as Adam Audio SP-5

I would consider Audeze LCD-MX4 the closest headphone to Ollo S4x in terms of overall signature / tuning, but the difference in price makes the comparison a bit useless. If you’re curious, MX4 has more detail, but if you look at the prices of both, and listen to them next to each other, changes are you’ll go home with S4X and rock them on. Makes you wonder what’s up with “4X” and “X4” being in the name of both. 

Ollo S4X vs iBasso SR-2 (400 USD vs 500 USD) – SR-2 is more comfortable, larger and easier to recommend for long hours of listening. They come with more extras and the sound is more laid-back, more natural, and with much more treble sparkle. The bass is actually a bit smoother on SR-2, and S4X makes itself remarked for actually having a bit more detail and revealing textures more. The soundstage is larger on SR-2, with a more precise stage for S4X. I think that if you want an easier experience, you will surely go for SR-2, while if you want a more precise ergo less musical experience, S4X should be the one for you. 

Ollo S4X vs Sivga P-II (400 USD vs 400 USD) – Sivga P-II is more comfortable, with better overall ergonomics, better overall build quality, and better default cable. The sound is more detailed and cleaner on S4X, with a smaller soundstage, but more precise instrument placing. By comparison, Sivga P-II sounds much larger, with more emphasis on musicality, more overall bass, more impact and better dynamics. The treble extension is also a bit better on Sivga, and the whole listening experience is closer to a live interpretation, while S4X is clearly a studio experience that’s hard to miss. 

Ollo S4X vs HIFIMAN Deva (400 USD vs 350 USD) – Deva has a much larger design, with larger and more comfortable cups. It also leaks much much more, and isolates much less, despite being bluetooth enabled. The soundstage in particular is impressive on Deva, with a much larger presentation, better instrument placing and more air / space between instruments. The sound is thicker, more precise, more impactful in the lows and mids for S4X. S4X reveals more details, and it reveals textures better, but also reveals mistakes in production and mastering much better. Deva sounds musical, open where S4X sounds precise, detailed and clear. 

Ollo S4X vs Adam Audio SP-5 (400 USD vs 500 USD) – Adam Audio SP-5 is the only headphone in this list that’s a fair match for S4X because both are designed for studio usage. Adam Audio SP-5 is the same headphone as Ultrasone Signature Studio, and they both have dynamic drivers also. The comfort is considerably better for Ollo S4X, with a better overall design, softer earpads, better default cable. The package of both SP-5 and Siggy Studio is much better. The sound of Adam SP-5 is extremely bright, with very little bass, and a brittle midrange. The whole signature can have a larger soundstage than S4X, but the S-Logic technology only works for some people, while for others it doesn’t. The whole detail level is better on S4X, the sound is more natural and more even. It tends to have more textures and can be listened for a longer time on S4X. Adam Audio is considerably brighter with more emphasis on treble impact, and if you’re afraid that your mix has too much highs, it is a better can to use, but S4X is a better fit for most studios and creators who want to just make, mix and master music. 


Recommended Pairings

The pairing list will include iBasso DX220 MAX, Singxer SDA-2 and FiiO M11 PRO. You could pair Ollo S4X with virtually anything, but smartphones generally won’t do and will be too quiet and weak / lifeless to sound good. I would go with more portable sources too, like FiiO M6, or a high-end DAC/AMP seen in music production like Mytek Brooklyn DAC+ if you need the ultimate pairing. 

Somehow, S4X is really consistent across sources, especially in tuning, so it will sound pretty similar regardless of the source you’re using. 

Ollo S4X + iBasso DX220 MAX (400 USD + 1880 USD) The first pairing is with the best DAP, the DX220 MAX. This pairing has the best dynamics, best impact and the most detailed sound you can get from S4X and a portable. On the other hand, it is not the brightest out there, and you will really need to dial in some highs via EQ if you’ll want to take advantage of more treble. DX220 MAX works as a USB DAC as well, and I will be reviewing DX300 soon too, so you can use it as the DAC for your workstation easily, which is why I consider it a good match for S4X. 

Ollo S4X + FiiO M11 PRO (400 USD + 650 USD) M11PRO also works as a USB DAC, so it can be a good workstation DAC, but it also has a brighter more open sound, and this pairs nicely with the thicker warmer and smoother sound of S4X. The overall detail level is really good, the pairing has a good soundstage, and a more airy presentation. Really recommended for both listening and mastering, as the final sound is quite balanced. 

Ollo S4X + Singxer SDA-2 (400 USD + 700 USD) Singxer SDA2 is the DAC/AMP to get if you want to have a large balanced headphone Amplifier, balanced DAC, if you have any decent studio monitors and if you don’t want to invest more than 1000 USD in the source. The sound of it is really natural, with a slight warm emphasis for the midrange, and pairing it with S4X results in a really clean and fun experience, a good amount of dynamics, a nice impact, and good overall control. 


Value and Conclusion

The value of S4X is actually excellent, they are a headphone with a lot going on for them, and despite the simple package, they really shine after you unbox them. 

I actually did complain about them quite a bit, as the lack of extra pads or cables is pretty disappointing, but they are a good headphone nonetheless. I am actually surprised myself to say this, but the sound, price, performance, everything is so good, that despite my complaints I feel compelled to add S4X to Audiophile-Heaven’s Hall Of Fame

The build is excellent, and despite them being on the smaller side, they are comfy, and they aren’t fully open. There’s some isolation, there’s a bit less leakage than most open-backs, and the wearing comfort is good thanks to the high-quality pads. 

The sound is flat, mid-forward, excellent for mastering, many hours of listening at once, but not perfect if you want a bit more treble, because it’s smooth up top. 

At the end of today’s review, I can totally recommend Ollo S4X, especially if you’re new to music mastering, mixing, or if you’re on a budget and need something that simply works, is high-quality and not so far from high-end headphones that cost thousands of USD. 


Product Link

You can purcahse Ollo S4X from their own website (Global) here: https://olloaudio.com/pages/s4x-reference-headphones

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Full Playlist used for this review

We listened to more songs than those named in this playlist, but those are excellent for identifying a sonic signature.  I recommend trying most of the songs from this playlist, especially if you’re searching for new music! The playlists are different for Spotify, Tidal and Youtube, and based on the songs I enjoy and are available on each!




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  1. […] list of headphones and IEMs used to test the DC03PRO includes OLLO S5X, OLLO S4X, Letshuoer D13, BQEYZ Topaz, KZ AS16 PRO, Audeze MM-500, Westone MACH 60, HIDIZS MD4 , iBasso […]

  2. Jerry

    Nice review! Those are exactly what I needed ! 🙂

  3. Andrew Master
    Andrew Master

    Awesome review! I just received them, and they’re the best thing that happened to my studio. Thanks a lot for answering my mails, and for all your guidance!

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