Aurorus Audio Borealis Review

The Aurorus Audio Borealis has been making waves across a number of enthusiast communities for some time, and while I got a chance to hear it at a meet near the end of 2019, this is a headphone that’s had quite a long development process. The guys from Aurorus Audio are in many ways enthusiasts turned manufacturers, and like other examples of this, much of the focus gets put on meticulously tuning the headphones to reach an agreeable frequency response. 

Aurorus Audio is a small company based in the Unites States (their headphones are made there as well), and while they're fairly new to producing headphones, they've generated a fanbase among core headphone enthusiast communities. They currently have two headphones available, one open and one closed.

Their open-back model, the Borealis, has been on my radar for some time, but it's also been somewhat elusive for me to get my hands on for an extended period of time simply due to its limited availability. Now that it’s been released, however, and some customers already have them, one was kind enough to send one in for review.

Specs

• Style - Open Back
• Driver - 50mm dynamic drivers
• Impedance - 32ohm impedance
• Cable - 6’ TRS (3/4”) terminated cable (Audeze/ZMF compatible)
• Price - $899

Sources

• iFi Pro iDSD -> Cayin IHA-6
• iFi Pro iDSD -> SPL Phonitor X
• Mytek Liberty DAC
• Auris Audio Euterpe
• Earmen TR-Amp
• iFi iDSD Micro Black Label

Build, Design & Comfort

In my mind the biggest obstacle to get past with the Aurorus Audio Borealis is its build and style. This looks and feels like a quintessentially ‘boutique’ style headphone, where the manufacturers had to rely on doing things themselves rather than relying on mass production. It’s also clear by the look and feel that the primary focus for this headphone is on sound quality - as it should be.

The top headband is a strap made from what appears to be a seatbelt type of material, and it’s affixed to the sides of two metal rods on the sides that hold the headphone together and create the clamp angle. Speaking of which, I find that while the Borealis isn’t the most lightweight headphone, it’s reasonably comfortable for a long period of time, without any clamp force issues whatsoever. I do notice that over time the cups start to sag down on my ears a bit, causing me to have to re-adjust where the strap connects to the rods, but it’s not a big problem.

Performance

The Borealis is an open-back dynamic driver headphone that uses the same off-the-shelf Tymphany driver that’s found in the Kennerton Vali headphones - so this doesn’t use any unique or fancy diaphragm materials like Beryllium to get the job done. Instead, the Borealis causes us to ask the question of what’s possible for sound quality with a more traditional transducer, as long as the headphone’s tuning is well done. And, on that front, the Borealis does not disappoint. It has to be said that for the most part, the Borealis performs better than its price point of $900 indicates, and I find that it competes with headphones that cost quite a bit more. In many ways, this evaluation isn’t a question of whether or not the Borealis’ sound quality meets its price tag, but rather how far can it go beyond that.

Detail Retrieval

For detail, image clarity, textural nuance and structural definition I find the Borealis to be easily appropriate for its price tag, however I find that the sense of details is partially also enhanced by some of its other qualities like speed and instrument separation. When I compare it directly to the (much more expensive) Focal Clear, that internal sense of detail and image clarity is noticeably better on the Clear - especially for the mids and bass. But with that said, the Borealis still does an exceptional job of making it easy to isolate individual lines and look into the music to analyze all the different layers.

Speed & Dynamics

I find the Borealis to have an excellent sense of speed and immediacy for the initial leading edge. This is a very fast sounding dynamic driver headphone. Importantly, it’s also got excellent dynamics. There’s a strong sense of punch and impact to bass tones, giving it a satisfying thump. Again, for Dynamics the Borealis competes with headphones that cost twice as much, if not more so.

Soundstage & Imaging

While the Borealis doesn’t sound intimate or claustrophobic to me, it’s definitely not the most spacious presentation. I find it to be slightly larger than that of the Focal Clear, but not by much. Importantly, however, in my mind the Borealis’ shining quality is its instrument separation and distinction. Usually this is a quality I associate more strongly with planar magnetic headphones, but the Borealis shows that it’s possible to get excellent image distinction in dynamic driver headphones as well. In my mind this is also one of the reasons for the added sense of detail - you have an easier time identifying all the details in your music because they’re so well separated from each other.

Timbre

I have to admit that I’m a bit disappointed by the Borealis’ timbre. I was hoping that due to its frequency response it would have a kind of naturalness and realism to it that existed with Sennheiser HD580, but I find that it has a kind of dryness to it that doesn’t quite work for me. To be more specific, it sounds almost as if everything is being pulled too tightly or strained a bit. But with that said, it’s still more natural sounding than many planar magnetic headphones, so it’s not that it has bad timbre, just that I was hoping it would be top of the class here and to my ear it’s not.

Frequency Response & Tonality

The following is how the Borealis measures on the GRAS 43AG standardized measurement rig relative to the combined Harman target curve (Harman 2013 bass but Harman 2018 mids and treble). For reference, the Harman 2018 bass is substantially elevated - far too much for what I think most audiophiles would consider appropriate, even if some bass heads may like it, so I prefer to use the more modest 2013 bass shelf. In any case, these are raw measurements, meaning it should not look like a flat line across. This instead shows the raw measurement relative to the target that would otherwise be normalized in compensated measurements.

How do you read this? The dotted black line is the target (how we might want it to measure), and the green line is how the headphone in question measures. Effectively, this shows how significantly the headphone’s frequency response deviates from the target.

Borealis Default Pads vs Harman Combined

In general the Borealis has an excellent frequency response. The bass follows the 2013 Harman shelf impressively well, yielding possibly some of the best bass response for an open-back dynamic driver headphone. While it doesn’t extend as far down into the sub-bass as most planar magnetic headphones do, this is still quite good, and importantly the shelf comes down at an appropriate spot before any bleed into the midrange.

For the mids, there’s a slight emphasis around 1.5khz that does get to me on certain recordings. There’s a bit of nasally or honky tone to certain instruments, but it’s not too significant. What’s great about the rest of the mids though is that they have an appropriate elevation at the primary ear resonance above 2khz, and things are basically perfect up until 5khz.

And speaking of which, the 5.5khz peak we see on the graph is audible to a certain degree, however once again this only shows up as a percussion compression on certain recordings. I find that for the most part this is still on the right side of that, and not something that intrudes on my enjoyment of the music often.

The rest of the treble response is also excellent, and impressively close to that of the Focal Utopia. There’s no sibilance issues or anything that sounds harsh or fatiguing, and then there’s ample air quality above 12khz to give a good sense of openness and resolution.

The bottom line is that apart from two minor issues, the Borealis has an excellent frequency response that fits with what I’d consider typically neutral, and it sounds great with just about all genres. In particular though I found it most enjoyable with acoustic and instrumental recordings - and not just because I happen to like that stuff, but more so because it appropriately follows the ear-related gain factors in the upper midrange, and this type of tuning really brings out resonant tones for acoustic guitars.

If that doesn’t sound like something you want, it’s also possible to pad swap, and while some may enjoy different presentations you get from changing the pads, I found that no matter which pads I used, I ended up preferring the stock ones. For example, when switching to the ZMF Universe Perf Suede pads, I found that it just accentuated the 5.5khz peak a bit too strongly, and this was a common theme for most of the pads I tried.

Borealis ZMF Universe Suede vs Harman Combined

EQ

While the Borealis doesn’t require EQ to sound good, I do think it benefits from a few adjustments, namely by reducing 1.5khz by about 2dB with medium-wide filter, and then reducing the 5.5khz peak also by about 2dB, this time with a more narrow filter.

Comparisons

While the following comparisons are totally unfair price-wise, in my opinion it’s worth considering them simply because when it comes to the notion of an ‘all-rounder’, the Borealis performs quite well. I consider these options also great 'all-rounders', and while I do rate them all higher than the Borealis, it's worth having that conversation to see just how close the Borealis comes.

Focal Clear ($1499)

While both have an excellent frequency response, I find the Borealis to be slightly behind the Clear when it comes to technicalities, although slightly ahead for soundstage. I prefer the Clear’s handling of the bass and midrange, even though the Borealis also has excellent bass response. The Borealis has a better treble presentation to my ear - that is, at least above 5.5khz. The Clear by contrast has a slight peak at around 6khz and a bit of a sharp sounding bump at 8.5khz, while the Borealis is a bit smoother in that region. So overall, the Clear is I think the next step up from the Borealis, but it’s surprising how close it comes.

ZMF Auteur ($1599)

The main difference between the Auteur and the Borealis is that the Auteur has a more spacious presentation, and a noticeably more natural and ‘euphonic’ sounding timbre. This may have to do with its slightly slower decay, or maybe it’s taking on some properties of the wood - but in general I find the Auteur to also be slightly more enjoyable than the Borealis for those qualities. At the same time, the Borealis sounds faster and tighter to me - with a bit more impact in the bass. Both have an excellent frequency response and tonal balance throughout.

Focal Utopia ($4000)

This is a totally unfair comparison, but I just wanted to note again how close to the Utopia the Borealis’ frequency response is in the upper mids and treble. The one important difference is the Borealis’ 5.5khz peak, but apart from that it’s nearly identical. With that said, the Utopia is clearly better for detail retrieval, but it’s still impressive that the Borealis is able achieve that kind of familiarity.

Conclusion

The Borealis has several knocks against it that should be considered. Its look and build doesn’t exactly indicate ‘premium’ the way a more refined production and manufacturing process might. There’s a strong ‘boutique’ element to this headphone that may be off-putting to some. If you can get past this, or you find yourself able to appreciate the uniqueness of it all, then the Borealis is a great sounding headphone that easily gets my recommendation - especially as an ‘all-rounder’. It’s not the best at any one thing in particular, but it does just about everything really well, and it does so with a generally agreeable frequency response.

-Andrew Park (@Resolve)

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