Ollo Audio X1

Crafted to Reveal — Listen to Your Music Like a Pro

So, If music is a window onto the soul — as the cliché goes — then for me, studio reference headphones are a window onto the soul of the mixer and producer who help make that music. I feel there is no better way to understand music at that deep level than through a headphone built for that purpose, and few headphones make the case for that idea as compelling as the Ollo Audio X1.

So, in this review, I will compare the X1 with some other studio headphones in my collection and hopefully give you a proper feel for whether this is the right headphone for you.

Ollo Audio is a small Slovenian company whose handcrafted open-back headphones circulate earnestly among mixing engineers rather than appearing in mainstream online stores. The X1 is their flagship open back, with American walnut earcups and a five-year warranty that reflects genuine confidence in long-term durability. One nice thing that drew me to it immediately was that each unit has a unique calibration, a profile derived from measurements of your specific pair, for use with the included USC II software plugin.

I have been listening to the X1 for about 6 weeks now — at my desk, as a dedicated music listening tool (using the USC II tool provided with the X1) but also just relaxing each evening with it paired with various amplifiers. Unlike most studio reference headphones, the X1 with its wooden cups also looks great just sitting on my coffee table waiting to be picked up:

What I found most surprising during the review period is that the X1’s character in use sits somewhat differently from what the word “studio reference” might lead you to expect — it is a more musically engaging and texturally warm-neutral tuning that reminded me more of a Meze headphone than say a Sennheiser HD600, though the provided personalised calibration brings the sound back toward a more neutral tuning.

While I really liked listening to the X1, I do have a few ‘quibbles’ about the experience and I will get to them during the review. But first let’s take a look at what’s in the box.

Unboxing and Packaging

The packaging signals a European boutique manufacturer rather than a consumer electronics company and I mean that as a huge compliment:

The box is clean and purposeful — no lifestyle photography, no hyperbolic marketing language — and the structural quality of the packaging communicates that what is inside deserves careful handling.

Opening the box reveals Ollo Audio commitment to ‘perfect’ tuning, that little box has your specific headphone calibration details:

Removing this cardboard layer reveals the carry case underneath with a warning about clamping pressure:

The carry case is reasonable good quality and will easily protect the X1 on your travels:

Opening up the case finally reveals the X1 looking well:

In the little box you get a registration card with serial number, and a calibration details card with access to the USC II software licence which I will get to in detail later in the review:

Overall, a decent unboxing experience.

Build Quality and Design

The first impression of the X1 in hand is of genuine artisan manufacture:

The American walnut earcups — CNC-machined from a single piece of wood — have a warmth and presence that no moulded plastic or anodised aluminium can replicate, and the consistency of grain and finish across the pair suggests care in selection rather than random batch processing.

This is a headphone that looks as considered as its engineering claims to be.

The open-back grill design allows the 50mm angled driver to be partially visible — and that angled orientation is deliberate, aimed at improved stereo imaging and a more natural soundstage presentation relative to a driver mounted perpendicular to the ear.

The depth of the earcup cavity is notable — generous enough to accommodate most ear shapes comfortably without the ear contacting the driver housing:

The walls are lined with a combination of acoustic foam and artificial leather that seals without aggression:

The dampening material inside the earcup:

Removing the earcups — which is straightforward and by design — reveals the driver assembly cleanly, and the entire disassembly process makes visible what Ollo Audio means by user-serviceable:

This is a headphone built to be repaired, not discarded.

This is even more impressive when you spot the various user-accessible and standard screws, one of the X1’s most quietly impressive features; should anything happen beyond the 5-year warranty it will be easy to repair:

I believe every component of the headphone — drivers, backplates, sockets, earpads, headband — is available to purchase as a spare part from Ollo Audio directly.

In contrast, while writing this review, I nearly laughed out loud when I read that the latest Audeze LCD-5s headphone release needs to be sent back for a pad swap. But Ollo Audio’s commitment to user serviceability is both rare and practically meaningful.

Headband

But as I mentioned earlier, I do have a few things I think I should flag about the X1, so first, I am not a massive fan of the stainless steel headband (though I love the subtle brand ‘X’):

The material is a little heavy, and this combined with the wooden cups makes the overall weight of the X1 heavier than I would have liked, I measured it at 416g:

But with that said, this material does give the X1 a ‘built like a tank’ feel. This headphone will take lots of abuse without falling apart, which is exactly what it would need in a recording studio:

But, the elastic stretching strap works very well (similar to Meze’s self-adjusting mechanism):

And the leather material on the strap does a nice job of distributing any pressure on your head and gives it a premium feel:

Another minor quibble is that there is a faint metallic clink when the metal hardware makes contact with the wooden earcup when you swivel the headband to adjust it:

But, the headphone elastic extension and swivel mechanisms together provide a very adjustable experience for most head sizes, though the X1 does have a notably higher clamping force out of the box, especially on my larger than average head. Though, after a few days I didn’t notice the clamp any more.

The cable

The cable is another area where I have a quibble. It is a nice very distinctive looking cable with the bright red design, but Ollo Audio has opted for a bespoke dual 2.5mm locking connector on the earcups, which is smaller than the dual 3.5mm standard used by most other studio headphones.

This means aftermarket cables are less readily available and more expensive than they would be with a more common termination. The absence of a balanced 4.4mm option is an additional omission for desktop users running balanced sources.

Though, I love how well the wood looks at each hole for each connector:

Comfort and Weight

The X1 is comfortable in the ways that matter most for extended wear: the earcup depth is generous, the elasticated headband distributes weight evenly across the crown, and the earpad material has a softness that does not degrade over an hour-long session. The earcup size is medium — adequate for most ear shapes and generous in depth, but not quite in the same league as the truly enveloping pads found on a Meze or ZMF earpad.

But at 416g, it sits on the heavier end of the open-back studio spectrum right up there with some Audeze headphones. For comparison, here are 2 popular alternatives the HEDD D1 and the HD490 Pro:

To put the weight in context: the Hedd D1 comes in at 345g and the Sennheiser HD490 Pro at a noticeably lighter figure still. These are real differences you feel over a long session. The X1 prioritises structural integrity and that mass is partly the cost of the stainless steel hardware and solid walnut construction — both of which contribute to weight.

USC II Calibration Software and Personalised Calibration

I would not normally dedicate a full section to companion software when reviewing a wired headphone — software comes and goes, apps get abandoned, and a headphone should stand on its own. But the USC II tool that ships with the X1 is a genuinely interesting tool to use and, since the headphone comes with a calibration file, it is worth applying that factory-measured calibration and listening to how it sounds.

But for me, it was a fun way to spend a few hours listening to how some of my favourite recordings sounded in various ‘profiles’ that a Producer or Mixer might use. For example, switching to various spatial profiles. Here is a short video showing some of the options available:

The fact that the calibration file is a compensation file for your specific unit is something that you rarely see. This matters in practice: driver variation within a production run is real, and correcting for it at the individual unit level is a great value-add.

The USC II plugin applies this correction during playback, and it does so with a calibration intensity slider running from 0–100% rather than a binary on/off switch — which is a thoughtful implementation that lets you blend the corrected and native response rather than forcing a hard choice between them. That alone would be a compelling feature. What makes USC II genuinely enjoyable to spend time with is everything built around it.

The plugin offers a set of listening modes — Flat, Studio, Car, Spatial, and Harman target — alongside mixing utilities including mono/stereo soloing and an EQ tilt control. Each mode applies a different target curve or room simulation on top of the calibrated response, and the effect of switching between them while a familiar track is playing is immediately audible. Studio brings a controlled, treated-room character; Spatial widens the presentation; Car applies a more compressed, forward response; Harman pulls the response toward the well-known consumer preference target. None of these are gimmicks. They are tools that let you hear the same recording through a different interpretive lens — and that turns out to be a genuinely useful thing to do, whether you are mixing or simply listening for pleasure.

What I found myself doing, more than I expected, was using USC II as a way to rediscover my music collection. Running through albums I know well in Studio mode, then switching to Spatial or Harman, reveals details in familiar recordings that the same track played on a fixed headphone without any of these tools does not surface in the same way. The plugin integrates into both standalone playback and DAW environments, which makes it equally practical for mixing sessions and casual listening. The basic licence included with each X1 covers the individual calibration and all of the core modes — no paywall, no subscription — which is exactly the right decision for a product at this price.

Sound Impressions

All listening impressions were formed over a month of daily use, sourced primarily from a FiiO desktop DAC-amp feed from my Macbook Pro with the calibration loaded but without any of the effects the USC II software can apply. I also listened most evenings without the USC II to get a feel of the headphone without any ‘EQ’ calibration.

Impressions, below are formed without USC II active unless otherwise stated, as I wanted to understand the X1’s native character before assessing the calibrated version.

The overarching character of the X1 is warm and detailed — closer to an engaged, musical listen than the clinical monitor presentation the “studio reference” category might imply. The comparison that felt most accurate during my time with the headphone was: this is what it sounds like when a mixing engineer has tuned a headphone for the way music should feel to work on, not just the way it measures on a chart. That distinction matters, and it explains both why I found myself returning to the X1 for pleasure listening as much as reference work, and why the X1’s sound character will not satisfy listeners seeking the strictest analytical neutrality.

Bass

The bass character of the X1 leans warm — a slight mid-bass elevation gives kick drums and bass lines a satisfying body and weight without crossing into bloom or looseness. Sub-bass extension reaches to approximately 35Hz before rolling off, which covers the practical range of most music effectively, though it falls short of the extension that makes some competing open-backs exceptional for electronic material. The texture within the bass region is commendably clean — microdynamics in bass guitar lines and acoustic double bass are rendered with genuine articulation rather than smeared together — and the overall low-end character contributes to the X1’s engaging quality without undermining its monitoring usefulness. Led Zeppelin’s “Ramble On” is worth reaching for here, where the organic string texture of John Paul Jones’ bass is rendered with an authenticity that makes the recording sound newly present rather than merely familiar.

Midrange

The midrange is the X1’s most accomplished region, and the aspect of the sound that most clearly distinguishes it from competitors at similar prices. Vocal timbre is convincing and immediate — voices sit close and naturally present, with harmonic richness that gives female vocals in particular a textural depth that is genuinely involving. Instrument separation across the midrange is precise without being forensic, and the note weight and body that acoustic instruments carry gives recordings a sense of physical reality that more analytically tuned headphones sometimes lack. This is what the X1 excels at in practical use: returning to familiar recordings through the X1 reveals textural details in midrange content — guitar voicings, piano overtones, the character of a particular singer’s upper register — that other headphones present accurately but less vividly. Joni Mitchell’s “A Case of You” demonstrates this particularly well; the vocal intimacy and the subtle textural details in her voice are rendered with a naturalness that rewards close attention.

Treble

The treble is extended and airy without tip-toeing into etch or glassiness. The X1 avoids the upper-harmonic aggression that makes some studio headphones — notably the Beyerdynamic DT 1990 Pro — fatiguing over extended sessions, while retaining enough air and shimmer to render cymbals and high-frequency transients with genuine fidelity. Treble extension is sufficient for mastering applications, and there is no sibilance issue with recorded vocals even on brighter material. The overall treble character is smooth and unhurried, more interested in the natural decay of a sound than in highlighting its initial transient attack. Nils Lofgren’s “Keith Don’t Go” is the reference track for assessing this balance — the high-harmonic shimmer of the acoustic guitar sits naturally rather than pushed forward, and cymbal decay is convincingly rendered.

Soundstage and Imaging

The open-back design and the angled 50mm driver combine to produce a soundstage that is consistently good for a studio headphone — wider and more layered than most closed-backs without extending into the artificially diffuse presentation some open-backs produce at this price. Instrument placement is precise, with a well-defined centre image and clear left-right separation. Depth layering is the area where the X1 most rewards careful listening: on complex recordings, the sense of front-to-back distance between instruments is more convincing than the price might suggest. Supertramp’s Crime of the Century — the classic test for spatial presentation — rewards the X1’s depth rendering with a convincing sense of the recording space that the angled driver geometry contributes to meaningfully.

Comparisons

Here are some other Studio reference headphones that I have reviewed previously, the Sony MDR-MV1, Hedd D1, Sennheiser HD490 Pro, and Audeze MM-100 each of these headphones (and the X1) provide a strong cross-section of what the modern studio reference open-back segment has to offer and as I said in my intro can be a ‘window into’ the intentions of the mixer, producer, or studio engineer who used them in the recordings.

Each is excellent in its own right and arrives at the studio reference designation by a different route. What follows is how the X1 sits among them.

Ollo Audio X1 vs Hedd D1

The Hedd D1 shares the open-back reference headphone positioning but arrives at a different point on the tonal spectrum. The D1 is measurably more neutral — closer to a flat target — and its ultra-thin membrane air motion transformer driver produces transient speed that the X1’s 50mm dynamic cannot fully match. Against the X1, the D1 sounds drier and more forensic, particularly in the bass and lower midrange where the X1’s warmth gives recordings a more organic character. Comfort is more straightforwardly easy on the D1 — the clamping force is lower and longer sessions pass without adjustment. For the strictest analytical monitoring work, the D1 holds an edge in neutrality; for the kind of music enjoyment that reveals details without sacrificing engagement, the X1 makes a stronger case.

Ollo Audio X1 vs Meze 109 Pro

The Meze 109 Pro is the closest tonal relative in my collection to the X1 — both occupy a warm, detailed presentation that prioritises musical engagement over strict flat-line accuracy. The X1 differentiates itself most clearly in the midrange, where it has greater presence and harmonic richness compared to the 109 Pro’s slightly recessed mid character. The 109 Pro’s wooden earcup construction gives both headphones a similar aesthetic philosophy, but the 109 Pro wears more gently out of the box and its comfort is less conditional on head size. For listening pleasure, both are excellent; for midrange-critical work, the X1 is the more revealing tool.

Ollo Audio X1 vs Sony MDR-MV1

The Sony MDR-MV1 is an interesting counterpoint to the X1’s philosophy. Sony designed the MV1 around 360 Reality Audio spatial playback as well as conventional stereo monitoring, and its frequency response is flatter and more extended than the X1 — measurably closer to a diffuse-field neutral target. At 223g it is also nearly half the weight of the X1, and wears with a lightness that makes very long sessions genuinely effortless. What it gives up against the X1 is tonal colour and engagement: the MV1’s presentation is precise and truthful, but it does not make familiar recordings feel newly present in the way the X1’s midrange warmth can. For engineers who need the flattest possible reference tool and who do not need the per-unit calibration or the handcrafted provenance, the MV1 makes a strong case. For listeners who want a studio headphone that rewards pleasure listening alongside professional use, the X1 is the more involving companion.

Ollo Audio X1 vs Sennheiser HD490 Pro

The Sennheiser HD490 Pro is perhaps the most direct practical rival to the X1 at this price tier — both are positioned as open-back professional studio headphones with a strong emphasis on accuracy and long-term usability. The HD490 Pro ships with two sets of earpads (reference and mix), which gives it a degree of in-box tuning flexibility the X1 cannot match. At 270g it is also meaningfully lighter than the X1 and has a lower clamping force, making it the more straightforwardly comfortable studio tool for longer sessions. Tonally, the HD490 Pro leans slightly cooler and more analytically precise in the upper midrange and treble compared to the X1’s warmer presentation. The X1 counters with the individual unit calibration, the handcrafted build, and the midrange harmonic richness that gives the HD490 Pro’s presentation a somewhat drier character by comparison. Both are excellent professional tools; the choice largely comes down to whether you prioritise ergonomic ease (HD490 Pro) or tonal warmth and calibration depth (X1).

Ollo Audio X1 vs Audeze MM-100

The Audeze MM-100 brings planar magnetic technology into this comparison, and the character difference is immediately apparent. The MM-100’s planar driver delivers bass with the control and authority that planar designs are known for — tighter, more uniform sub-bass extension, less susceptibility to driver sag at higher volumes, and a microdynamic precision in the low end that the X1’s 50mm dynamic cannot fully replicate. In the midrange, the two headphones are competitive — the MM-100 has planar speed and precision, while the X1 has the harmonic richness and tonal body that gives voices and acoustic instruments a more organic character. At 392g the MM-100 is close to the X1 in weight, though it wears somewhat more comfortably thanks to lower clamping force. At a similar price point, the MM-100 makes the more technically exacting case for bass and transient handling; the X1 makes the more musically engaging case for midrange texture and the unique value-add of individual calibration.

Specifications and Measurements

Measurements

The Frequency response shows a very nice though slightly warmer midrange tuning, reminds me a little of some Meze headphonses with that warmth. The slight dip between 1Kz 2Kz is typical of a headphone that provides a soundstage effect and the treble extension is nice with nothing too dramatic that would cause sibiliant issues:

Here is FR normalised and compared to a ‘flat’ DF with a -10dB slope:

Overall, I feel this is a excellent warm-neutral tuning that will appeal to most audiophiles. The channel matching measurement is good — left and right channels track closely.

The loose versus tight clamp comparison is one of the more instructive measurements in this reviewL

As the graph illustrates, the X1’s response does change slightly based on clamp force, so those with larger heads might perceptually hear more upper bass warmth.

I measured both the raw and the calibrated response (so using the calibration file provided by Ollo Audio):

The calibration fills in that 1Kz-2Kz region significantly and lowers that lower midrange a little, bringing the overall tonality even closer to neutral. Roughly my specific calibration was this EQ:

The overall frequency response confirms the listening impressions: a slight mid-bass warmth, a well-behaved midrange, and a treble that extends with air rather than aggression. The response is warm rather than strictly flat, and the individual calibration in USC II brings this closer to the target — the combination of native character and software correction gives you a degree of control over the presentation that fixed-response headphones cannot offer.

The comparison against the Hedd D1 and Meze 109 Pro makes the tonal relationships clear. The X1 sits warmer than the D1 across the bass and lower midrange, with better bass extension than the 109 Pro while maintaining comparable warmth through the midrange. The midrange advantage over the 109 Pro is visible in the response — the X1 holds its presence region more assertively, which translates directly to the greater vocal and instrumental clarity in listening.

The distortion measurements are genuinely excellent and explain part of the X1’s character under real musical conditions. The 0.05% THD specification holds across the measurement, with distortion remaining well-controlled even in the demanding low-frequency range where dynamic drivers typically show the most stress. A low-distortion driver is the foundation on which everything else in the X1’s presentation rests — and these figures confirm that Ollo Audio has invested in a driver that earns its studio reference designation on measured merit, not marketing alone.

Rating Explanation

The X1 earns a pragmatic rating of four for a combination of reasons that are easier to feel than to enumerate. On paper it is a well-measured, individually calibrated, user-serviceable open-back headphone from a small Slovenian manufacturer — and all of that is true and meaningful.

But the thing that stays with me is the sense that someone actually made this, there is something qualitatively different about using a headphone where you can see the grain of the walnut, feel the solidity of the hardware, and know that your specific pair was measured and calibrated before it was sent to you. I felt it with the Mirph-1, with the Modhouse Tungsten, and with the Verum 2 — handcrafted headphones carry a different kind of presence in use, a sense that extra care went into their construction that a production line cannot replicate. The X1 belongs in that company, and that intangible quality is part of what the pragmatic score reflects.

The price rating of five needs little justification: at €539 for a handmade, artisanal wooden headphone with individual unit calibration, a five-year warranty, full user serviceability, and a 90-day money-back guarantee, the X1 is priced with genuine restraint. You are not paying a luxury premium for the wood and the craftsmanship — you are getting it at a price that would be competitive even for a mass-manufactured headphone with none of those features.

The measurements rating of four reflects the USC II calibration system as much as the raw frequency response: the combination of very low distortion, excellent channel matching, and a per-unit correction profile that you can blend at any intensity gives you a degree of control over the presentation that most headphones at any price cannot offer. That system is genuinely enjoyable to spend time with — exploring the Flat, Spatial, and mixing modes feels like using the kind of tool a producer or engineer would actually reach for, not a gimmick bolted onto the side of a consumer product.

The two genuine caveats sit in the features and comfort columns. The bespoke dual 2.5mm connector is the most frustrating detail on an otherwise thoughtfully designed product — aftermarket cable options are limited and finding a standard replacement requires more effort than it should. And while the weight of 416g is well distributed and did not cause me fatigue in long sessions, it is a fact of life with the X1 that lighter competitors — the HD490 Pro at 270g, the MDR-MV1 at 223g — simply disappear on the head in a way the X1 does not. For listeners for whom neither of those is a deal-breaker, the rest of the X1’s proposition is difficult to argue with.

Conclusion

The Ollo Audio X1 made me listen to my music collection differently, which is a high compliment for any headphone. The warmth and midrange presence that characterise its native tuning gave familiar recordings a textural engagement I had not heard through other references in my collection, and the USC II calibration system provided a meaningful additional layer of control for sessions where strict accuracy mattered more than enjoyment. Over a month of use, I reached for the X1 for pleasure listening as often as for reference work — which says something important about how the X1 sits in the headphone landscape.

This is not the headphone for everyone. The 416g weight makes itself known over very long sessions, and the warmer engaging character technically diverges from strict neutrality in ways that will matter to those obsessed with measurements. But for the listener who wants a handcrafted, individually calibrated, user-serviceable open-back headphone that reveals musical detail without sacrificing the pleasure of listening — and who is willing to have patience with the fit while the clamping force softens with use — the Ollo Audio X1 is a remarkable product at a price that is very difficult to fault. Buy it if you want to rediscover your music collection through ears that are simultaneously more honest and more musical than most.