Grell Audio OAE2

An Open-Back That Is Very Good for Everyone, and Exceptional When Its Angled Driver Meets the Right Ear

Spacious, open and superbly comfortable — and how spacious depends on how the angled driver sits against your ear — measured here rather than argued about.

Grell Audio is a young company — Axel Grell founded it in 2022 after a career at Sennheiser that produced the HD 580, the HD 650, the HD 800 and the Orpheus, which is the reason a small company’s second headphone gets this much attention. I reviewed the Grell Audio OAE1 last year and came away fascinated by its free-field tuning, extreme angled driver and deliberately tilted bass shelf, but it was never one of my more comfortable headphones. The OAE2 keeps the same bio-cellulose driver technology and design philosophy while fixing exactly that — Grell have clearly used what they learned to improve the parts that mattered.

This review is about two months later than it should have been. I was curious about how to present the differing opinions on the OAE2’s presence region and lower treble: some reviewers hear it as recessed, while I hear it as one of the best things about the headphone and part of the spacious presentation it shares with the OAE1.

My theory is that the steeply angled driver makes the response in that region particularly sensitive to how the cup sits against the ear. To explore that, I decided to write my own little ‘headphone positional variation measurement tool’, which I will show later in the review. It lets me compare measurements across different headphone positions, though it cannot capture every listener’s ear shape or explain every difference in opinion. I also plan to use it on other angled designs, including the recent Aune headphones, though nothing I have measured is angled as steeply as the OAE1 and OAE2.

Here is an image from my first listen to the OAE2 at Vienna High End — it was almost love at first listen:

The OAE2 looks almost identical to the OAE1 online, but it is a better headphone in the ways that matter most: noticeably more comfortable, with bass that trades quantity for real quality, and a presence region that measures very differently depending on exactly how it sits on your head — which may help explain why two people can listen to the same pair and disagree about the treble.

The positional quirk with the OAE2 is probably its most interesting aspect, but first, let’s take a look at what’s in the box.

Unboxing and Build Quality

The OAE2 arrives in a glossy black outer sleeve with a life-size photo of the headphone on the front, sitting over a plainer kraft shipping box underneath:

The back of the box carries the model number and regulatory information, while one side panel prints the full feature list and technical specification table — useful to have to hand before you have even opened the case:

Inside, a fold-out manual cover sits on top, printed in the same dark, minimal style as the rest of the packaging:

Underneath that is the carrying case itself, a slim, flat clamshell with the Grell logo on the lid — a much slimmer profile than the bulbous case you get with a lot of headphones at this price, and one that will actually fit in a drawer or a bag pocket:

Open the case and the headphones sit with the earcups swivelled flat, one of Grell’s two cables coiled neatly beside them, along with a card insert:

You get two cables in the box: a 1.8m balanced lead terminated in 4.4mm, and a second 1.8m single-ended lead terminated in 3.5mm with a screw-on 6.35mm adapter — between the two, that covers most of the DAPs, dongles and desktop amps you would plausibly want to pair this with:

Build quality is a clear step up from what photos suggest — like a lot of gear, the OAE2 looks better in person than in the marketing shots. The earcup grille is a fine stainless-steel damping mesh made in Germany, held in a silver-finish ring, and it photographs cleanly straight-on:

Seen from the side, you can make out the depth of the grille assembly against the dark velour earpad — the driver sits well back from the mesh, which is part of how Grell get the angled, front-oriented driver placement their FSFM tuning depends on:

The headband yoke and slider mechanism is solid metal, with the leather-and-velour headband strap visible where it meets the frame:

Looking at the slider and headband arch on its own, the finish and fit feel considered rather than cost-cut — nothing about the adjustment mechanism feels loose or cheap:

Inside the earpad itself, the driver sits behind a fine acoustic mesh, with a clear “R” marking so there is no ambiguity about orientation:

The side panel lists a modular design intended to let every part be replaced, for long service life. Pads and cables are consumables on any headphone you keep for years, and a manufacturer saying out loud that the rest of it comes apart too is a better sign than any of the marketing adjectives above it on the same panel.

Grell’s own wording for the tuning philosophy is “front-oriented loudness diffuse field equalization”, with “adaptation to individual hearing curve: sound field–pinna interaction” underneath it — which is the long way of saying what FSFM, Front-sided Sound Field Modulation, stands for: aim the driver at the ear from the front and let the shape of your own ear do the last part of the equalisation. The positional measurements explore how the response changes as the driver moves relative to the ear on my rig.

One of my few real criticisms: the cable connects to only one earcup via a 2.5mm TRRS plug, with the signal for the other driver routed internally through the headband. It is a sensible enough engineering choice, but it is the same design decision I disliked on the OAE1, and it means the aftermarket cable market — which is enormous for standard dual 3.5mm connections — is effectively closed off to you here. The stock cables are fine, but I would still have preferred the simpler, more swappable dual-entry approach.

Fit and Comfort

This is where the OAE2 makes its biggest improvement over the OAE1, and it is not a subtle one. At 378g without cable it is not a light headphone. The specified headband clamping force is lower too: 2.5N, compared with 3N for the OAE1. For me, though, the OAE1’s main comfort problem was the headband material, and that is what Grell changed. Pictured directly against the OAE1’s headband, the OAE2’s padding is noticeably softer to the touch:

For me, that one change makes a real difference over long sessions — I would call the OAE2 genuinely comfortable, and clearly more comfortable than the OAE1. The original was okay for me but never one of my most comfortable headphones. There are headband designs, like those from Meze, that are more comfortable, but the OAE2 for me was a decent improvement over the OAE1.

The earpads themselves are large, deep, and fully surround the ear without resting on it, which is consistent with the angled, front-firing driver design carried over from the OAE1. Between the improved headband and the same generously sized pads, this is a headphone I can comfortably wear for a long listening session, and it is a clear step up from its predecessor.

Sound Impressions

After many months of listening and comparing the OAE2 with other review headphones, my conclusion is really that Grell have moved the tuning from “make you feel the bass” toward “get the balance right” — the whole headphone is better for it.

Before the detail, the plain statement: listening to this headphone is an absolute joy, and I am genuinely confused that it has not had more love. Grell have toned the bass down to what I think is exactly the right level, and the result is very likely to be my open-back headphone of the year.

Bass

The bass on the OAE2 is a genuine quality-over-quantity story compared to the OAE1. There is less sheer low-end lift, but what is there is tighter, better controlled, and more textured — this is a headphone that gives you good, clean bass rather than a bass shelf designed to impress on first listen. On “Way Down Deep” by Jennifer Warnes the low end has real weight and definition without ever feeling like it is reaching for drama it does not need, and the mid-bass stays out of the way of the vocal rather than crowding it.

Midrange

The midrange is carefully balanced, and it is where the OAE2 does its most convincing work. Vocals and acoustic instruments come through with a natural, unforced quality — nothing pushed forward for effect, nothing recessed either. On “Sweet Jane” by Cowboy Junkies the vocal sits with real presence and body, and the surrounding instrumentation stays clearly layered around it rather than competing for space.

Treble

Treble is spacious without tipping into fatigue, which given the OAE1’s more relaxed, free-field-influenced top end is a meaningful shift rather than a small tweak. There is enough air and extension to keep cymbals and detail present, but nothing sharp enough to wear you down over a long session. On “Roads” by Portishead the treble has room to breathe without ever turning splashy or hot, which suits the spacious character of the rest of the tuning.

Soundstage and Imaging

The angled, front-oriented driver placement that defined the OAE1 carries over here, and the payoff is the same speaker-like sense of space, now sitting on top of a more coherent overall balance. Imaging is accurate and the presentation opens up beyond the earcups rather than sitting inside your head. On “Private Investigations” by Dire Straits the spacious presentation and the precise placement of the guitar and percussion work together convincingly, giving a real sense of depth without ever feeling artificially inflated.

Comparisons

The most relevant comparison is obviously the OAE1, since the two share a driver and a design philosophy while landing in noticeably different places. Looking at the two side by side, the family resemblance is clear from the earcup grille and driver placement, but the detail differences are where the story is — the OAE2’s headband frame finish differs from the OAE1’s, and it is a small but telling sign of how much Grell iterated on the details between generations:

Looking at the two from the top, you can see how similar the overall silhouette remains — this is very much an evolution of the same design rather than a ground-up rework:

The earpads tell a similar story of careful refinement rather than reinvention — both are generously sized velour pads, but placed side by side you can see the OAE2’s shaping is subtly different:

And the driver grilles — silver-ringed on one, differently finished on the other — make for an easy visual way to tell the two apart at a glance if you ever have both in front of you:

Sonically, the two are close relatives rather than twins: the OAE1’s tilted, elevated bass and more relaxed presence region give way on the OAE2 to a more controlled low end and a fuller midrange, while both retain that distinctive front-oriented soundstage. If you found the OAE1 interesting but wanted something more universally easy to enjoy day to day, the OAE2 is the more complete headphone.

Beyond the OAE1, four headphones from the wider collection are the most useful reference points for the OAE2: the Sennheiser HD600, the Hifiman HE600, the FiiO FT7, and the HEDD Audio HEDDphone D1.

Against the HD600, the comparison is really a study in two different definitions of “accurate.” The HD600 remains my benchmark for pure midrange and treble tonality — beautifully balanced, if narrower in soundstage — but its bass is deliberately restrained, more about precision than presence. The OAE2 gives you more low-end body and, thanks to its front-oriented driver placement, a noticeably more open, out-of-the-head presentation than the HD600’s more traditional, in-head imaging. Neither makes the other redundant; they simply chase different goals well.

Against the HE600, the OAE2 trades the Hifiman’s planar-driver bass extension and treble energy for a warmer, more organic overall character. The HE600 is more linear and technically extended in the bass, and its treble carries more sparkle and micro-detail — exciting on the right recording, but also the more fatigue-prone of the two on hot masters. The OAE2’s spaciousness comes from a completely different mechanism than the HE600’s planar-driven width, and where the HE600 sounds more analytical, the OAE2 sounds more relaxed and inviting over a long session.

Against the FT7, the comparison is the closest in philosophy of the four. FiiO’s flagship planar also prioritises bass accuracy over quantity and pairs it with a spacious soundstage, which is exactly the OAE2’s own pitch. Where they part ways is in character: the FT7 is the more neutral, reference-leaning of the two, while the OAE2’s bio-cellulose driver and front-oriented tuning give it a more distinctive, speaker-like personality. If you want the most “correct” sound, the FT7 edges it; if you want the more interesting listen, the OAE2 does.

Against the HEDD D1, the OAE2 meets its closest rival in ambition, if not in underlying technology. The D1’s Thin-Ply Carbon Diaphragm gives it a midrange that is genuinely class-leading, with a wider, more three-dimensional soundstage than the HD600 and bass that is tight and honest rather than elevated — much the same “quality over quantity” bass philosophy the OAE2 is going for. The OAE2’s midrange is very good but does not quite match the D1’s exceptional tonal density, though the OAE2’s front-oriented driver placement gives it a different, arguably more directly speaker-like spatial presentation than the D1’s more conventional driver geometry achieves. Both are headphones built around a novel diaphragm technology, which makes them an unusually interesting pair to own side by side.

Specifications and Measurements

Grell’s own spec sheet, printed on the side of the retail box, is unusually detailed about the sound-shaping philosophy behind the FSFM driver placement and the stainless-steel damping fabric — see the packaging photo above for the full text.

I have started measuring the OAE2 myself. Before settling on a single reference curve, I ran repeat measurements across several refits and positions to check how consistent the seal and placement were — the overlay below shows those runs together, and they track closely except for a region between 6kHz and 10kHz that needed a couple of extra passes to fill in properly:

Here is the reference curve I settled on, a stock left-channel capture plotted inside the preference bounds:

Read on its own this is a well-behaved open back: a gentle lift through 40–60 Hz, a smooth downward slope through the midrange, and a broadly even run from 1 kHz to 5 kHz that stays inside the bounds for most of its length. On this seating, the presence region does not look strongly recessed. The positional measurements show how much that response can change when the cup moves.

On drive requirements, the spec sheet is enough to settle it: 100 dB at 1 kHz for 1 Vrms into 38 Ω. That works out at about 0.5 Vrms, or under 7 mW, for a loud-enough 94 dB, and roughly 3.2 Vrms for a peak-handling 110 dB. A desktop amplifier capable of that voltage has enough headroom, and most modern dongles will manage sensible listening levels — but the headroom above that is where a weak source runs out, so a phone headphone jack or an older dongle is the case to be careful about rather than the rule. It is also a fully open back with essentially no isolation, so none of this applies on a train in any case.

Most of the listening for this review was done from the FiiO K17 R2R, which has more than enough voltage for an open back of this sensitivity and takes the amplifier out of the argument:

Positional Variation Measurements

That repeatability overlay was the first hint, and it is what sent me off to build a better instrument. The measurements below come from a tool I wrote for the purpose, the Headphone Positional Capture. The idea behind it is deliberately narrow: make it simple to take a centred measurement plus a forward and a backward one, plot them together against the target and its preference bounds, and see what actually moves. The point is never any single curve. The point is how far apart the family is, and where.

The specific question I built it to answer on this headphone was whether shifting the cup forward or back fills in the treble region. Here is the answer, normalised at 500 Hz:

It does. From 20 Hz to about 1.5 kHz the traces sit almost on top of each other, within a decibel or two — the bass changed little across the positions tested on this rig. Then from 2 kHz upward they separate, and the widest spread lands squarely on the ear-gain peak around 3 kHz and the region above it out to 6 kHz, where the family covers roughly three decibels. Move the cup and that region fills in or empties out.

That graph offers a possible explanation for the differing listening impressions. Reviews of the OAE2 disagree about the treble to a degree that is unusual even for this hobby: some describe it as massively recessed and conclude the tonality is simply wrong, while others, me included, find the tonality exceptional. Position could contribute to that disagreement, alongside ear shape and preference; these measurements cannot establish how each reviewer wore or heard the headphone.

For comparison on the same fixture, here is the same measurement run on the Meze Strada, a closed-back with a conventional, not steeply angled, driver. I moved the Strada to the same range of positions on the fixture, and the differences that followed came from how completely the cup sealed at each one:

The Strada shows the opposite pattern, and a more serious problem of its own. Below 100 Hz its traces spread by six or seven decibels, and that is a seal issue: each new position broke the seal to a different degree, and a closed cup’s bass is only as good as its seal. But through 2 to 5 kHz, the region where the OAE2 moves around, the Strada’s curves stay bunched within about a decibel. Two headphones, two opposite signatures. The Strada’s variation is consistent with changes in seal; the OAE2’s is consistent with my hypothesis about the angled driver, though this comparison does not isolate driver angle as the cause.

One caveat about reading these plots. The two are normalised at different frequencies, 500 Hz for the OAE2 and 1 kHz for the Strada, and a family of curves is always tightest near its normalisation point by construction. That explains some of the OAE2’s tightness around 500 Hz and some of the Strada’s around 1 kHz. It does not explain the OAE2 holding together from 20 Hz to 1.5 kHz, and it does not explain the Strada spreading by six decibels at 20 Hz while staying inside a decibel at 3 kHz. The patterns survive the caveat.

Their actual responses differ as well as their positional behaviour:

Below 100 Hz the sealed Strada has the greater lift, which is what a closed cup buys. From 200 Hz to 1 kHz the Strada carries more energy, which is the lower-midrange warmth that defines it. Through 2 kHz to 5 kHz the OAE2 holds the steadier line while the Strada dips further. Two good headphones with genuinely different emphases, and an argument for owning both rather than choosing.

The usual limits apply as well: this is a KB501X soft ear and pinna with a 711 clone coupler, not your head. Positional results are rig-dependent, and above 8 kHz the response is especially sensitive to the coupler, pinna and placement, so I would not treat the individual peaks and dips as precise predictions for a listener. What these measurements show is a mechanism, not a prediction for any one listener. The observed variation could help explain why listeners disagree, but it does not settle the question for everyone. On my head, the presence region lands where I like it. On someone else’s it may not.

For me, this headphone doesn’t need EQ — the presence region lands perfectly on my head, so I won’t suggest a PEQ change. But I thought it might be useful to reference oratory1990’s PEQ, so here it is:

You can find the full PEQ settings here.

Distortion

I ran a harmonic distortion sweep on the same rig, with the fundamental sitting between 91 and 101 dB SPL across the band — louder than I normally listen:

Distortion is concentrated in the low bass, with lower harmonic levels through most of the midrange and treble. The sweep is at a higher level than my normal listening; I did not hear distortion as a problem in use. The graph alone does not establish that every component is inaudible on music.

Rating Explanation

The Pragmatic Rating of 5 reflects a headphone that took what was interesting but flawed about the OAE1 and improved the parts that mattered. The bass moved from “make a statement” to well-judged, the midrange is a real strength, the treble is spacious without being fatiguing, and — for me at least — the OAE2’s comfort is a clear improvement over the OAE1 through a softer headband material rather than a cosmetic tweak. The Measurements score of 5 reflects what I believe Axel Grell was always aiming for with this driver and tuning approach.

The Features score of 4 comes with one real caveat: the single-sided 2.5mm TRRS cable connection is a sensible engineering choice but a genuine practical limitation, since it locks you out of the huge aftermarket dual 3.5mm cable market that a lot of headphones at this price can freely use. The Price score of 4 is not really a knock on the OAE2 itself — at €499 it remains a strong proposition — but the OAE1 spoiled all of us on what Grell Audio could do at this price point, and if you like a little more visceral bass, the OAE1 is an incredible bargain.

This one is for anyone who found the OAE1 interesting but wanted something easier to live with day to day, and for anyone starting fresh who wants a distinctive, front-oriented open-back with good bass quality and a comfortable long-term fit — though given how much comfort opinions seem to vary head to head with this design, an in-person try before buying is a sensible precaution.

Conclusion

The Grell Audio OAE2 is everything I had hoped for from Grell Audio’s second headphone: it looks similar to the OAE1 at a glance, but it is a better headphone once you actually live with it. The bass swaps quantity for quality, the midrange and treble are spacious without tipping into fatigue, and — for me — the comfort is a clear step up from the OAE1. Even after 3 months and many other review headphones, I am still reaching for the OAE2 regularly, which is the simplest evidence I can offer that Grell got the important things right this time. At €499/$499, I think it is my open-back headphone of the year. It won’t be for everyone, as those placement measurements show, but if a comfortable placement of the OAE2 on your head works like it does for me, you have a perfect headphone.

There are many headphones that measure well but sound harsh or dull when you listen to them. I think the achievement with the OAE2 is that this headphone sounds great for most people, with its linear bass and excellent midrange, and will sound extraordinary for many, assuming your ears align with the angled drivers the way Axel Grell envisaged them to.

Put the OAE2 and the Sennheiser HD 480 PRO, or even the HD600, on a table, let the house go quiet in the evening, and nine times out of ten I reach for the OAE2 — that openness and bass response combined with this tonality beats even the best-tuned closed back or even the legendary HD600 without using some bass EQ. That is not a criticism of the Sennheiser and it is not a ranking. Pick the headphone that gives you the most spacious, open sound, the one that properly tries to reproduce the sound of speakers in a room. Pick the OAE2.