OLLO Audio X1

OLLO Audio’s eco‑friendly headphones certainly stand out from the crowd. Do they sound as good as they look?

There are lots of ‘boutique’ manufacturers making high‑end outboard, mics and monitor speakers. In part this is because although components such as loudspeaker drivers and microphone capsules are difficult for small outfits to produce in‑house, they are readily available as OEM parts. Boutique headphone manufacturers are much more unusual, but OLLO Audio definitely belong in this category. Based in Slovenia, OLLO have a very individual philosophy which is centred around meeting the specific needs of musicians and producers, rather than the wider hi‑fi market, in the most sustainable way possible.

Consequently, you’ll search in vain on the OLLO website for Bluetooth or active noise cancelling. What you will find, however, is a full set of spare parts still available for every model that OLLO have ever produced, right back to the original open‑backed S4 and closed‑back S4R, reviewed in SOS January 2020. These are now discontinued, and OLLO’s efforts are now all focused on a new model they call the X1. This is available only in an open‑backed format.

High Calibre

Perhaps the most significant development that has taken place since 2020 is that OLLO have formed a partnership with headphone correction specialists dSoniq. Each pair of X1 headphones is paired with an individual calibration file, created using “the power of AI processing”, and a licence for dSoniq’s USC II. This is a cut‑down version of their Realphones software, and the calibration file can also be uploaded into the full version if you have it. Better still, since the calibration file is supplied in the standard XPS format, it can also be loaded into hardware audio interfaces from RME, Neumann, UA, MOTU and so on.

Handbuilt in small batches, the X1 is a more or less conventional moving‑coil design, but the drivers are housed in distinctive circular earcups made from wood. As on the S4, these are suspended symmetrically from the headband, meaning that they are not ‘handed’ as such; the right earcup is whichever one you connect the right side of the supplied Y‑shaped cable to. And, unfortunately, the indication of left and right on the cable itself is still needlessly hard to discern.

At the same time, the X1 also differs from the S4 in several important respects. The pegboard‑style outer surface of the earlier model’s earcups has been replaced by a new design, where sound exits through a cutout shaped like a stylised letter X. The wire headband on the S4 has been abandoned in favour of a metal strip with cutouts in it, presumably with the aim of reducing the unwanted resonances that made the earlier design problematic. And whereas the S4 models came only with a soft bag, the X1s are supplied with a proper, semi‑rigid fitted carry case with handle.

OLLO don’t just talk the talk when it comes to sustainability. They back up their philosophy with a limited five‑year guarantee, and say that all components on the X1 should be replaceable using simple home tools. The apparent build quality would suggest that their confidence is justified; perhaps because of the new faceplate design, the X1s retain the very individual character of the S4s whilst shedding any vestige of a ‘homemade’ aesthetic.

Drive Time

Internally, the X1s employ “custom‑made low‑impedance drivers”, with a 50mm membrane that has a “composite Pu+PET patented pattern”. It’s not clear whether these are actually manufactured by OLLO themselves or simply made to their specifications, but either way, they are different from the drivers used in previous OLLO models, and deliver good numbers. THD and second‑order harmonic distortion are given as less than 0.05% and 0.02% respectively for a 1kHz sine wave at 94dB SPL. Nominal impedance is 32Ω, and the X1 will output 101dB SPL for a 1kHz tone at 1V RMS.

These figures are not so very different from those of the original S4, but that tells us little about how the two models sound. To my ears, the S4 had a rather unusual sound signature, with a prominent ‘upper bass’ and a noticeable suckout in the midrange. Their other good characteristics, such as low distortion, made them promising candidates as mixing headphones, but only with the help of software frequency correction. That wire headband was also troublesome, with even slight touches inducing very audible, undamped ringing.

In comparison, there’s a night and day difference with the X1. Firstly, the new flat headband still transmits mechanical noise, as all such types do, but it’s now effectively damped, so you’re never left wondering whether the resonances you’re hearing are present in the source or not. And secondly, the headphones themselves sound completely different. In fact, when I first got them out of the box and tried them, I hadn’t yet found out about the bundled calibration options, and my first thought was that they sounded really quite flat and neutral in their raw state. There was none of the aggressive upper‑mid splashiness or ‘smile curve’ tonality that you so often find in even quite high‑end headphones, especially models designed for music listening as well as studio work. The only slight departure from neutrality I could readily detect was a hint of additional warmth somewhere in the 300Hz region.

The corrected X1 felt both natural and confidence‑inspiring to work with. Even uncorrected, they were closer to my perception of ‘flat’ than many other open‑backed designs.

Registering the X1, downloading the XPS file and installing USC II then made a subtle but wholly positive improvement, taming that slight midrange thickness, firming up the upper midrange and bringing up the low bass a shade. Loading the XPS file into the full version of Realphones revealed that only four EQ bands were active: a 2.3dB cut at 364Hz, a comparable boost at 1600Hz, and equally gentle shelving boosts and cuts at the low and high end respectively. It’s an interesting alternative approach to something like Sonarworks’ SoundID Reference, which generates highly granular EQ curves; whatever the pros and cons, the corrected X1 felt both natural and confidence‑inspiring to work with. Even uncorrected, they were closer to my perception of ‘flat’ than many other open‑backed designs.

The bundled USC II calibration package is a cut‑down version of dSoniq’s Realphones.

USC II also gives you a limited but useful subset of features from the full version of Realphones, most notably a selection of target curves and binaural room simulations that includes a virtual studio control room. Like the full version, it will run either as a plug‑in in all the major native formats, or as a ‘systemwide’ standalone version with a virtual audio driver.

With the X1, OLLO Audio have proved that a start‑up with original ideas and an individual philosophy can absolutely compete head‑on with the titans of headphone monitoring.

Counter Culture

As I noted at the start of this review, if you’re hankering after a new mic, a fancy equaliser, a desktop synth or a pair of speakers, there’s plenty of leftfield and niche options out there to complement the established names. If your quest is for a new pair of studio headphones, however, the field is much narrower. With the X1, OLLO Audio have proved that a start‑up with original ideas and an individual philosophy can absolutely compete head‑on with the titans of headphone monitoring. These are every bit as good as other models I’ve tried in the same price bracket; they’re built to last and backed with a five‑year guarantee; and although they barely need software correction, you get it thrown in for free. Impressive!

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