Axel Grell is a legend in the audio world. He's a German headphone designer and acoustic engineer who created some of the most beloved audiophile headphones still used today. The 1997 Sennheiser HD 600 is still the gold standard for a natural-sounding midrange. The HD 650 (a warmer HD 600), the HE 1 (a mere $60,000 to you) and the HD 800 S (famous for its soundstage) all have his fingerprints on them. So when Axel makes a headphone, you pay attention. Today the Grell OAE2 goes on sale, and I've been testing a pair for the last two weeks.
It's a uniquely built, highly enjoyable, yet imperfect headphone. It's worth its $599 asking price for the right owner (though definitely look at my list of the best budget audiophile headphones for more affordable ideas). Positioning its drivers in each ear cup far forward, facing back, the OAE2 attempts to mimic the experience of listening to a pair of loudspeakers at a 30º angle. That physical design effects the headphone's soundstage and to a lesser extent its frequency response. Like I said, it's uniquely built.
Driver & housing: 40mm bio-cellulose dynamic
Material: Steel earcups, polyamide structure, velour/Memory Foam padding
Cable: 1.8 metres; 1x 3.5mm single-ended with 6.3mm adapter, 1x 4.4mm balanced
Impedance: 38Ω
Sensitivity: 100 dB (at 1 kHz, 1 VRMS)
Weight: 378g
Price: $599 / £549
The root of the OAE2, and the 2024 OAE1, lies in Axel Grell's personal history. Once upon a time, he built loudspeakers, and before that he mixed the live sound of his university band, then came headphones. It is with his original love of speakers that the designer thought up the OAE series.
Yet it's not all sunshine and rainbows. The OAE1 was a bit of a flop for many audiophiles, with some wincing at a shouty 6kHz upper midrange peak, and others declaring 'too much bass' (as if there is such a thing!) However, I haven't heard that version, so I'll be reviewing the OAE2 by itself, and in comparison to some of Grell's best headphones to date that I have used.
Grell's philosophy
Before we get into how the Grell OAE2 sounds, it's important to talk about what Axel Grell's aim is with these headphones. After all, if he wanted to create a supremely natural-sounding traditional headphone for a new generation of music lovers, he could have just copied his own homework, and recreated the HD 650/600, but with an added bass shelf.
Errr, and that's kind of what he's done... but we'll get to that.
By placing both dynamic drivers at the front of the headphone ear cups, and directing them back, the OAE2 is breaking with the accepted philosophy of how to make headphones.
Grell wants to mimic how you'd hear sound from near-field studio monitors, placed at a 30-degree angle. That is the 'natural' way to hear music, he thinks. After all, your brain has spent its entire life processing how your specific ears filter sound coming from the front. Not from all directions, as with traditional headphones.
The OAE series is his move to the 'correct' way to listen to music, with headphones. He wants the OAE series to present space fundamentally differently to all other traditional headphones... which is utterly baller, if nothing else.
Soundstage
By making the sound interact with your outer ear (pinna) before entering your ear canal, Axel is hoping that your brain will receive the spatial cues it needs to perceive a soundstage positioned in front of you, rather than inside your skull (as with all other headphones).
So, does he succeed? Yes. But it's a refinement, not a revolution.
With my ears, the OAE2 definitely presents music with more depth and more width in front of me than the HD 650, HD 600 or HEDD D1 – the main sets I compare the OAE2 to below. But temper your expectations. I've seen videos and read what seem like paid-for articles, that state this is a seminal progress in soundstage. For me, it's an incremental improvement. The difference is real, and depending on the recording, it can be really meaningful, but generally it's quite subtle. It's also worth noting that you get more from the OAE2 the more time you put in. As with all critical listening, the more you focus, and the more you know what you're focussing on, the more you get from it. That's the case with the soundstage of the OEA2. Don't think you're going to just whack them on and have yourself an 8D music epiphany.
One thing worth noting is that Grell has mentioned there may be some brain burn-in required to get the most out of the OAE series. That is, a listener may need time to pick up on the directional cues and fully benefit from the positioned drivers. I think there's something in this, and I am definitely more attuned to the positioning of sound with the OAE2 after two weeks of using them. However, I still think the end result is subtle. Ultimately, this is something that you will have to determine for yourself.
Sound profile
Overall, the Grell OAE2 is a neutral/warm headphone that's great fun to listen to – especially at loud volumes! It has a good bass extension, so you get some rumble of the sub bass as well as the punch of the mid bass. I think the midrange is solid, and though not quite at the heights of the Sennheiser HD 6x0 series, it's strong. And then a (mainly) chilled out treble... as long as you don't have an issue with a slight peak around 5-6kHz. The man himself wasn't a million miles off when he compared the OAE2 to the HD 650, but with bass.
Bass: The bass of the OAE1 was universally panned for being too heavy-handed. And although I haven't heard that headphone, I can read a frequency response graph, and the OAE1's chart does indeed look a little unhinged (though for the record, I quite like unhinged bass – see my favourite budget headphone, the FiiO FT1 for proof). Ultimately, it's hard to do bass with open-back headphones. It's even harder to do bass well. A lot of open-back bass rolls off below 70Hz. This bass digs deeper, and it's a noticeable win for the OAE2. But how has Axel Grell done it?
He's developed a new damping system using a specific stainless steel mesh that lowers the driver's resonance to 40Hz. That means he doesn't need to add wads of bass in the 70-80Hz region, which would noticeable yet muddy (it's a tactic in headphone tuning, so the listener experiences bass, but it's not actually articulate or detailed.... it's half-arsed bass). With the OAE2, the extended bass offers a fuller picture of what bass really has to offer – more of that rumbly sub bass, as well as the more punchy mid bass. End result is, while this is definitely not a basshead set, it passed all my bass-heavy test tracks by giving me the feel and the detail of the bass notes, whether that was string bass or 808s.
I use the Luxsin X8, Chord Mojo 2 and Fosi DS2 DAC/Amps for all my headphone and IEM reviews. This ensures sufficient power delivery for peak performance, while providing a distortion-free source for a clean, detailed signal. My music sources are Spotify Lossless and CDs.
Midrange: It would be pretty odd if a headphone made by the man who tuned the HD 6x0 series didn't have an excellent midrange. Looking at a FR graph comparing the OAE2 and HD 650, there may be deviations between the two, but not around the 200Hz to 1kHz range. That is to say, the majority of the midrange is natural, if a bit warm.
So, is the OAE2 an HD 650 with a bass shelf? No. The HD 650 (for all its faults, which I detail below), still offers a more natural tone and timbre in the midrange. Still, 23 years after it was first tuned, it reigns as the warm natural midrange to beat (and the same goes for the 1997-made HD 600, if you don't want that warmth).
However, at roughly 5kHz in the lower treble, or presence region, things get a little shouty on some of my test tracks. I first noticed it in the clarinet solo passage on Me and My Friends' Before I Saw the Sea. The song is an excellent melee of mids, and it's useful to see if a headphone has any particular peak of interest in the 1-6kHz region. If you're sensitive to this region, it's certainly something to think about.
Treble: Things are pretty relaxed in the treble region. Grell has been vocal about his dislike of artificial air – of adding high treble to a headphone to trick the brain to think there's more resolution and detail than there is.
I hate to disagree with a legend, but I think airy treble can be done really well, (have a look at my review of the Binary Acoustics EP321 for more on that sound profile) and can be part of a very enjoyable audio experience. However, I will concede that it is often not executed well, and the result can be shrill and unpleasant (Beyerdynamic, I'm looking at you).
Either way, the OAE2 is tuned to sound like a pair of loudspeakers in a treated room, and so there is a roll off in the treble. If the track that you're playing wasn't recorded with added treble bite, you won't be hearing it with the OAE2.
Perhaps because of that lack of treble sparkle, which usually scratches the itch for perceived detail in a track, I often found myself wanting to notch the OAE2 up just one more decibel… And maybe because of the frequency response, and the driver positioning, I got away with doing it in every listening session. These things just invite you in to whack the volume up!
If this is more than just my personal depravity, then that's something that you should think about before buying these headphones. After all, we are talking about the health of your ears here.
Price, value & comparisons
The Grell OAE2 retails at $599 in the US, and £499 in the UK, so it's a chunk of change wherever you are. Is it worth it? Essential to answering that is to evaluate the competition, and unluckily for the OAE2, its creator has made some absolute bangers around this price. Another company has also recently released a classic of its own. In short, competition is fierce!
It makes sense to talk about the HD 650. Axel made it in 2003, and it's one of my favourite headphones. I love its warmth and its the clear, forward vocal presentation, so much so I don't usually don't miss its lack of bass. Regularly selling for $370, this is significantly cheaper than the OAE2. For under $400 you will get a similar clamp force to the OAE2, a cheaper-feeling headphone (a lot more plastic and less metal), and no headband hotspot.
But the OAE2 offers that bass that the HD 650 has been missing for several decades! It also offers a similar midrange, for the most part, but there is a bit of a discrepancy around 5kHz – there's touch of shout with the OAE2 that isn't there with the HD 650.
And then there's the added depth and width of the OAE2. It is most noticeable with something like the HD 650, with it's very intimate sound profile and famous 3-blob effect (with sound distinctly coming from the left, right and centre).
But is it better?
I don’t think this music presentation of the OAE2 is inherently better or worse than something like the HD 650. It might seem like a cop out, but I had an absolute blast comparing them, and it comes down to a matter of taste. I will say, if you're worried that that added depth or width is in any way distracting, it's absolutely not.
When comparing the OAE2 with the HEDD D1 – my current go-to reference headphone – this is where I start to see the weaknesses of the OAE2. Or at least what I admire so much with the D1.
The D1 doesn't have the depth of the OAE2, but it has the width... but that all becomes academic as I just end up enjoying every single instrument so much.
The D1 offers a resolution that the OAE2 cannot offer (doesn't want to?). Each instrument is clearly conveyed, and has space around it. With the OAE2, things are more spread out, but also less crystal clear.
And when you consider that the D1 has plenty of articulated bass, it's a bit more of a fair fight than the HD 650. The D1, in many ways, is the HD 600 with a bass shelf and a little more detail (that is, airy treble). It's not warm like the OAE2 or the HD 650, but it's not clinical or bright. It's as close to perfect as my ears have heard... and yet it's $799, so definitely a step up in price.
So, it comes down to what you value, what you want. Depth and a relaxed sound profile? The OAE2 wins. Detail and a sense of space around each instrument? The D1 leads the pack. More intimacy, and lush, rich vocals? The HD 650 and 600 still reign supreme.
Comfort
This is where the most noticeable weakness of the OAE2 lies.
First the positives: The velour and memory foam ear pads are cushy enough to fall out of my mind after a minute's use, and although many criticised the first iteration for its heavy-handed clamp force, I didn't have any issue with that. My brain found it easy to interpret the OAE2's not-the-heaviest-yet-beefy 378g as just a good quality build (even though most commercial headphones hover around the 200–300g region). I guess it's funny how generous your brain will be when it's enjoying music.
But I had a hotspot right on the top of my head that, at times, detracted from my enjoyment of using the OAE2. It wasn't there for every session. But when it was, it was very uncomfortable.
Will this be the case for all users? I have no idea. I'm not particularly prone to hotspots, and when there's a good weight distribution mechanism on a heavy headphone – such as the insanely heavy Audeze Maxwell 2 that is 563g, yet has an effective suspended headband – I don't experience them. It's worth noting though.
Why four stars & should you buy?
I really like this headphone, so why didn't I give it the full five stars? Well, I took half a star off for the hotspot the headband gave me, and half a star because, as great as it sounds, I definitely foresee a fatigue factor of always listening to it really loud, which the OAE2 invites me to do (it's the headphone's fault, not mine!)
For $599, there are options that do different things better than the OAE2. The HD6xO series gives you a more natural timbre, and sells for $200 to $300 cheaper. If you want resolution and detail, the Hifiman Arya Stealth is a well reviewed headphone for around $500 (though I've not tested them).
However, I can still see the Grell OAE2 being perfect for many people. If you like warm-neutral, can handle the specific upper-midrange that the OAE2 is putting down, and if you connect with the subtly different way that the music is presented, I could see this being someone's favourite headphone. For me, it'll definitely be a one I come back to – if not just to crank up the volume!
