Grell Audio OAE1

Ignore the hype (and the backlash) and enjoy a very different sounding headphone

After spending more than a month listening to and researching the audio science behind this headphone as well as trying to understand its recent reception by the audiophile community, two thoughts came to mind—both from my background in the computer industry.

The first was Steve Jobs’ iconic “Think Different” campaign when he returned to Apple. That was a rallying cry to challenge the conventional (Windows PC) with something very different (Mac’s), and the sound signature with the OAE1 certainly challenges current headphone conventions, trying to imagine something better by rethinking the familiar.

The second was the Gartner Hype Cycle, that classic curve we apply to emerging technologies. In many ways, the launch of the OAE1 mirrors that cycle: an initial buzz and curiosity and a peak of inflated expectations, and this was followed by a ‘backlash’ but as always with hype cycle, the truth is somewhere in between these two extremes.

But while I love the science behind its tuning, I do think the OAE1 will always be a headphone that will have both haters and those that enjoy it immensely, as Mac computers do compared with Windows Computers.

So, after spending nearly 6 weeks with the OAE1, I have many thoughts, and those thoughts have evolved over these last few weeks hence while this review has taken so long to write. But the most obvious thought is that this is not a headphone designed to appeal to traditional “headphone people” and especially headphone reviewers’ accustomed to ‘conventional’ sounding headphones.

But that does not make the OAE1 a bad headphone, on the contrary, it makes it one of the most interesting recent headphones, but before I get into the sound and why I think this is a worthy headphone to consider, let me delve into my understanding of the science behind the OAE1:

Initial thoughts on the Science behind the OAE1

To really appreciate this headphone, you do have to ’think differently’ about how headphones should sound. The OAE1 has 2 key ‘unusual tuning’ features:

1. Deep extened Bass
2. Free Field Tuning rather than a Diffuse Field tuning

Both of these are designed to give this headphone something unique, to give it a more ’live concert’ like audio experience and one that you might get with a great speakers’ setup.

Part of the reason it took 6 weeks to write this review was, I spent many days listening exclusively (while working) to my best speaker setups and then to the OAE1 in the evening. I have ‘full’ room correction setup in a few rooms with multiple sub-woofers correctly ‘blended’ with some nice full range speakers. In the main listening room, I have full Dirac room correction with correctly crossed-over KEF subwoofer with a pair of KEF LS50 Meta’s giving me a very neutral ‘flat’ in room response with very little ‘room modes,’ with a slight bass boost to my preference.

Room modes and what is correct Bass?

This setup where I treated the room is to remove the typical ‘room modes’ and correctly blended the subwoofer into the over sound from the KEF speakers. I think this is important as most Harman-tuned headphones have that ‘dip’ in the midbass to create an artificial separation between the subbass and the midrange. I believe for many people this ‘dip’ gives that sense of ‘a room sound,’. They are effectively used to listening to the ‘bad’ effects of speakers in a room e.g. ‘Room modes’ where there is typically a drop in the mid-bass frequency response due to reflections in a room cancelling each other out.

So while I do believe it is ‘right’ to have a target like Harman that is based on preference, it may not be as accurately represented as the most correct bass response from a well-tuned speaker in a room.

Circle of Confusion

I also believe Flood Toole’s ‘Circle of Confusion’ is another factor that greatly affects people’s perception of the OAE1. The extreme angled driver and the associated ‘free field’ tuning aim to reproduce a better simulation of the ‘real soundstage’ effect than any diffuse field tuned headphone, but almost every studio monitor headphone and even the ones used in the Harman research used diffuse field, assuming that the sound comes from all angles simultaneously. Most traditional headphones also have drivers pointing directly at the ear.

This is that ‘conventional’ sound that we are all used to hearing with ‘conventional’ headphones. It is a challenging trend for the OAE1 to overcome since most music (especially more recent music) is already recorded for using headphones with this assumption that it ‘sounds’ good on a diffuse field tuned headphone. But in my subjectively listening sessions, I did find many pieces of music that just sounded better with the OAE1 (I would guess these recordings where master using only speakers).

New trends in popular Target Curves

I mentioned earlier that the Harman mid-bass dip is probably more a result of people’s perception of what they think is correct, but one very interesting trend in IEM target curves (and the most recent audio science research from Sean Olive) is that the new ‘JM-1’ target got equal satisfaction to the ‘Harman target’.

The JM-1 target has effectively 2 big changes over Harman IE 2019 target, it has a warmer linear bass response (though peoples preferences will often give it a 10dB or more tilted bass) so no ‘Harman mid-bass’ dip, and it has a more relaxed / darker and therefore less ‘detailed’ for treble.

This trend gives me much hope for headphones like the OAE1, though possibly it will be the next Grell Audio headphone (maybe a OAE2?) that will get the full benefit of hindsight around having 2 very different alternative tunings where both can be ’normal.’

Note: How much of a bass ’tilt’ is correct is very debatable, but I believe Axel wanted to give the Bass on the OAE1 extra ‘oomph’ to make you ‘feel’ the bass, but my personal preference would be slightly less bass but still a warmer linear bass than Harman. I am a fan of some of the more recent Meze headphones as far as that midbass response. I do also like the bass on the FiiO FT1, and as you will see later in the measurements section, these very different headphones have some similarities in the bass to the OAE1.

Free Field or Diffuse Field?

Other than the Bass, the other key audio feature of the OAE1 and probably the most interesting is that it chases a ‘Free Field’ response rather than a ‘Diffuse Field’ response to give that ‘speaker in a room’ sound.

Most headphones tuned with diffuse field are effectively like speakers pointing directly at your ears from 90 degrees with the assumption that there is no directionality possible with headphones, so the sound is assumed to come from all angles equally.

There is an assumption, that the sound hitting your ears from speakers comes from all directions, so this has been the ‘defacto’ convention with the tuning of headphones (and measurements of headphones), but the OAE1 has an extreme angled driver, with the assumption that the majority of the sound from ‘speakers in a room’ comes at 30-Degree angle and hit your ears from that angle.

So the free field tuning greatly affects the measured frequency response specifically you get a much more relaxed presense region, so for those used to ‘diffuse field’ headphones this will sound less detailed:

Note: I do find it interesting how the 1-2Khz region is also more inline with how the ‘soundstage’ headphones like the HD800 (and many Hifiman headphones) are tuned to create that ‘soundstage’ effect, but the free field tuning goes way beyond just that 1-2Khz region.

Note: I do find the difference, between the free field and diffuse field in the 6K-10K regions very interesting, While the free field is very recessed in all measurements and the OAE1, in my measurements, does mostly match this target in my ‘calibrated’ Measurement head. But when I manually listened to a sweep in this area, I didn’t preceive nearly as large a drop. So I believe, for me (as everyone’s HRTF will be different) the best response FR is somewhere between these 2 targets, especially with a headphone like the OAE1 designed specifically with an extreme angled driver. So, instead of a 10dB difference, I feel maybe 5dB gives me a typiucal flat sounding sweep similar to my speaker setup.

So, I would guess this is an ideal middle ground between diffuse field and free field target in this specific area. This is why I feel the alternative JM-1 target preference is also interesting and possibly relevant as it has a similar recessed treble though not as much as the OAE1.

But I am mostly subjectively interpreting the results I hear, so I would suggest watching Axel’s excellent presentation from Munich High-End:

Here is also a PDF describing in detail Target Curves Munich 2025.pdf.

Anyway, I hope the above section was somewhat informative. So, the question is does this very deliberate tuning make the OAE1 sound like ‘speakers in a room’ or more like a ’live concert’?

Let’s find out in the rest of this review, but before let’s see what you get in the box.

Unboxing and Build Quality

The Grell Audio OAE1 arrives with simple, minimalist packaging that reflects the design philosophy behind the product:

Removing it from the external cardboard box:

And on the back:

Opening the box reveals the uniquely designed headphones nestled securely inside:

The OAE1 includes:

• The headphones themselves with a
• The cable is unusually a 2.5mm to 3.5mm termination (2.5mm can be used into either earcup)
• Documentation and warranty information

The build quality is good for the price with a nice mixture of metal and plastic used, but it won’t be for everyone and it is a tough market with lots of new entrants. But I like how the Grell logo is subtly visible on the back of the drivers:

The headband is constructed from lightweight yet durable metal with reasonable comfortable padding.

Looking at the drivers, you can see the extreme angle of the drivers in ear cup:

Note: While this is unique, I do feel to be even more effective, the driver should be larger, for example, the sound stage effect on some of my Hifiman Planar’s greatly benefits from the larger driver and somehow fitting an even larger driver (or maybe a planar) at such an angle would I feel give an even better result (though the headphone might start to resemble one of the fun ‘Pud headphones’ experiments as it would need to very large).

The 2.5mm cable connection is secure (you need a good tug to pull it out to switch earpads), and the overall construction feels robust without being unnecessarily heavy.

Note: I personally would rather have had dual 3.5mm connectors for easy cable swapping.

Overall, I like it, but I do think the styling of the OAE1 won’t be for everyone:

Fit and Comfort

The OAE1’s unique design creates a different wearing experience compared to traditional headphones with extremely deep cushions due to the angled drivers:

But this also means the headphone is wider than other headphones, and it is not as comfortable as other earpad cushions with less ‘compression’ and there is also a pretty large clamping force:

For me, I had to have it at max extension to be comfortable:

So, if you have a huge head, you might struggle to fit the OAE1.

As mentioned above, the OAE1 positions its drivers in front of your ears, creating a gap between the driver and your ear. This approach offers some possible benefits:

1. Reduced ear fatigue - Your ears remain completely unencumbered, eliminating the pressure and heat buildup common with traditional designs
2. Natural ear resonance - Your ear’s natural acoustics remain part of the listening experience and is not ‘crushed’ into the earpad like on many other headphones.

But overall, I would say the OAE1 only gets a 5/10 for comfort for me.

Sound Impressions

As mentioned earlier, the OAE1 adopts a free-field tuning philosophy that prioritizes natural tonal balance and spatial realism over conventional headphone tuning but due to the factors I mentioned earlier (especially the ‘circle of confusion’ around recordings) it will sound very different than other headphones.

The result is a sound that often feels more like listening to full range studio monitors (with a bass boost) than typical headphones. But, I found they were exceptionally well-suited to Americana, acoustic, and live-in-studio recordings where nuance, air, and placement matter most. I also really like them with many older recordings from the 1970’s, where I would guess the priority of the producer and mixer was for great sound from speakers rather than any headphones. I guess this probably changed after the ‘Sony Walkman’ was launched.

Bass

The bass on the OAE1 is deep but clean, and speaker-like, offering definition and texture without artificial bloom or impact.

Test Track: “Misguided Angel” – Cowboy Junkies (The Trinity Session) • Bass guitar and kick drum sit exactly where they should: supportive, warm, but never dominating • There’s excellent delineation between low-frequency instruments, even in reverberant spaces • Sub-bass rolls off naturally, mimicking the presentation of open-baffle speakers rather than sealed enclosures

However, in the context of well-mastered Americana or alt-country, the OAE1 offers a truer representation of how bass sits in a live room or natural acoustic space.

Midrange

The OAE1’s midrange is compelling, rendering vocals and acoustic instruments with organic clarity and lifelike timbre.

Test Track: “Blue Ridge Mountains” – Fleet Foxes • Vocal harmonies are rendered with startling presence and dimensionality, never veiled or hyped • Acoustic guitar strums and resonances are rich in harmonic nuance, showcasing excellent transient response • String and brass instruments exhibit accurate tone and body, with no midrange congestion

This tuning flatters intimate recordings and minimalist arrangements, particularly those captured in real spaces with ambient cues intact. Americana, roots, and modern folk are particularly well-served, with no added warmth or peakiness to distort tone.

Treble

The treble response is refined but recessed, and deliberately non-fatiguing, emphasizing realism over sparkle, but it will sound less detailed on many recordings as for the reasons I mentioned earlier. I personally EQed the treble a little by hand to give back some of the detail in most recordings but in many tracks this was not needed.

Test Track: “Orphan Girl” – Emmylou Harris • Treble is clean and resolves micro-details (e.g., breath, string harmonics) without pushing them forward unnaturally • Percussion and ambient room cues are well-presented but never strident • There’s an airiness to the top-end that contributes to realism, not artificial brightness

This allows for long listening sessions, especially with recordings that are bright by nature. The OAE1’s top-end won’t gloss over poorly recorded content, but neither will it exaggerate it.

Soundstage & Imaging

The OAE1 offers a decidedly out-of-the-head experience and one of its defining traits, but I believe this might not be the case for everyone, if you are chasing that sound stage effect, it might be worth demoing the OAE1 first to be sure you HRTF is aligned with the tuning.

Test Track: “Wayfaring Stranger” – Johnny Cash (American Recordings) • Soundstage appears to project forward, similar to nearfield speakers rather than side-oriented headphone imaging • Instrument placement is natural and well-separated, especially in sparse arrangements • Ambient cues (e.g., room reverb, mic bleed) are rendered with lifelike depth and front-back layering

This is an ideal headphone for listeners who value recording space and depth—from Nashville studio takes to raw, intimate house concert recordings.

Technical Performance and Measurements

Specification	Details
Driver Type	Dynamic, front-mounted
Impedance	32 Ohms
Sensitivity	100 dB/mW
Frequency Response	10 Hz - 30 kHz
Weight	Approximately 320g
Cable	Detachable, high-quality OFC
Connector	3.5mm with 6.3mm adapter included

The OAE1 is relatively easy to drive, though it benefits from a clean amplification source. It doesn’t require as much power as most planar magnetic headphones, but a quality DAC/amp combination will help realize its full potential.

But I did run with various amplifiers in various setups in my house including my work from home setup:

And I also used my Macbook Pro and even my Apple USB-c dongle where both happily drove the OAE1.

Frequency Response

I measure the OAE1 on my KB501X soft ear pinna, and the measurements of these and many other headphones are availalbe here

Here is OAE1 on the measurment ear:

So, initially looking at the FR:

I highlighted the 2 areas discussed earlier which are the most distinct about this headphones.

One other interesting aspect of the headphone and one that will affect different people heads is the placement of the driver relative to your ear:

Specifically, if the headphone is pushed back or forward, so the driver is nearer or further away from your ear it will greatly affect that

I also measured altering the position vertically and this did not have as much effect:

Zooming in a bit I thought it might be interesting to compare the bass of the FT1:

Overall I think the OAE1 has excellent controlled tilted bass for an open back dynamic driver.

Next, since I do like (as do many other people) the warmer signature of many Meze headphones I thought comparing the bass would also be useful:

The Meze headphones have more variable bass (dependent on the model) but the OAE1 has better sub-bass and as I mentioned above a more linear bass response.

Basically, if you like a warmer linear but tiled bass response, you will appreciate the OAE1.

Finally, I thought I would compare the OAE1 with 2 of my ‘studio reference’ headphones, typically used my mixers and producers when mastering audio. This is more to illustrate that ‘Circle of Confusion’ i mentioned earlier as you can see wildly different bass and treble from these headphones, though I think it is interesting that the Audeze does go for a ‘darker’ treble response:

Distortion

For a relaetively small driver the OAE1 handles playing loud pretty well with some rise in the bass but nothing audible:

And shown as a percentage you can still see that the sub-bass does have a little bit of elevated distortion but less tha 1%:

EQ Suggestions

While the OAE1 is designed with a specific sound signature in mind, some listeners accustomed to more conventional headphone tuning might prefer a bit of EQ adjustment.

Here’s a simple parametric EQ that can help bridge the gap between the OAE1’s unique tuning and more traditional headphone sound, without sacrificing too much of Axel’s vision. I did lower the mid-bass a little as this is often what people expect and I brought the treble (at least to my ears) nearer to a diffuse field tuning in that area:

Suggested PEQ settings:

1. Low Shelf: 100Hz, +2dB, Q=0.7 (adds a bit more sub-bass impact)
2. Peak: 2.5kHz, +3dB, Q=1.2 (brings more presence to vocals and instruments)
3. High Shelf: 8kHz, +1.5dB, Q=0.8 (adds a touch more air and sparkle)

These subtle adjustments help the OAE1 sound more familiar to those coming from traditional headphones while preserving some of the spacious, speaker-like presentation that makes these headphones special.

Comparisons

Grell Audio OAE1 vs. Sennheiser HD600

The HD600, also designed by Axel Grell during his time at Sennheiser, provides an interesting contrast:

• The HD600 offers a more traditional headphone presentation though sometimes critised for having a 3-blob sound - left, right and center.
• The OAE1 creates a more speaker-like soundstage experience with sound appearing to come from in front
• The HD600 has a slightly more forward upper midrange and excellent tonality, it is what headphone people expect a headphone to sound like as far as the mid-range and treble
• The OAE1 offers far better subbass, while the HD600 excels in precision

Both headphones would make 2 excellent additions to a collection, each offering something very different yet interesting to alternate between while listening to your favourite music.

Grell Audio OAE1 vs. Hifiman Edition XS

I believe this is a good comparison as both headphones try to aim to provide that ‘soundstage effect’, the Edition XS does this with a mixture of extremely large drivers (in a large egg-shaped earpads) with some FR tweaks (borrowed from the Sennheiser HD800) while the OAE1 does this using the extreme angled drivers paired with a very accurate Free Field tuning. So technically will mimic the angle of typical speakers in a room.

The Edition XS soundstage is less accurate, with certain intruments appearing at odd ’extreme places’ within the sound stage, but it can be a ‘fun’ listen because of this. While the OAE1 tries to be much more accurate with the placement of intruments, but that often means it does not sound as impressively ‘soundstagey’ as the Edition XS.

Who Should Consider the OAE1?

I think there are four key challenges that affect how listeners perceive the OAE1:

1. Bass Response Expectations: The OAE1’s bass is more reminiscent of a concert hall experience rather than typical room listening. So as I mentioned above listeners are accustomed to the “bass tuck” found in Harman-tuned headphones, but the OAE1 does have a deep bass ’tilt’ so as well as the mid-bass some listening might perceive too much overall bass.

2. The “Circle of Confusion”: While Axel’s approach to the relaxed presence region (to account for the 30-degree driver angle) is scientifically sound ‘free field’, it conflicts with how most music is recorded and mastered. As audio scientist Floyd Toole has discussed in his “Circle of Confusion” concept, most recorded music is created using differently tuned headphones and monitors, so when played back on the more “correct” OAE1, it doesn’t always sound as expected.

3. Comfort and Fit Variability: For users with larger heads, the OAE1 can be tight even at maximum extension, potentially causing discomfort during longer listening sessions. Users with smaller heads will likely find them more comfortable.

4. Placement Sensitivity: The extreme driver angle that creates the speaker-like soundstage also makes the headphones very sensitive to positioning. Even slight shifts in placement can significantly alter the frequency response, particularly in the 2-3kHz region. This means some users may experience an unbalanced, “shouty” presentation if the headphones aren’t positioned optimally for their ear anatomy.

After spending significant time with the OAE1, I believe they’re particularly well-suited for:

• Live music enthusiasts: The OAE1’s bass presentation does an excellent job replicating the feel of live music, though not exactly the chest-thumping impact of a concert.

• Americana/Roots music fans: I found music recorded to sound like live performances (particularly American/Roots music) was exceptionally well-rendered through the OAE1. If this is your primary genre, these headphones deserve special consideration.

• Speaker enthusiasts: If you primarily listen to speakers and find conventional headphones unnatural, the OAE1’s spacious, front-focused presentation will feel more familiar and comfortable.

• Audio experimentalists: Those who appreciate the science behind audio reproduction and are willing to “think different” about what headphone listening can be.

It may be less suitable for:

• Listeners with larger heads who need extended comfort for long sessions
• Those who prefer the intimate, “in your head” presentation of traditional headphones
• Users who primarily listen to music mastered on conventional headphones without applying EQ
• Those seeking maximum bass impact and rumble - its bassy but not in a way that might appeal to ‘bass-heads’

Rating Explanation

I’ve given the Grell Audio OAE1 a 4-star Pragmatic Rating. Here’s why:

• Build Quality & Design: ⭐⭐⭐⭐ (Good craftsmanship and innovative design in this price range)
• Comfort: ⭐⭐⭐ (Good for most users, though potentially very tight for larger heads)
• Sound Quality: ⭐⭐⭐⭐ (Though not a conventional sound, it is excellent if you understand its intended purpose)
• Value: ⭐⭐⭐⭐⭐ (Excellent price for some unique audio technology)

The OAE1 mostly accomplishes what it was designed to do – using some clever audio science to - create a more speaker-like experience in headphone form, its extreme angled driver and free field tuning together with its bass shelf will always cause extreme opinions. For traditional ‘headphone people’ it will always sound so unconventionally different that it will continue to be a headphone that causes controversy.

But for the right listener, these headphones offer a unique and valuable perspective on music that few other products can match. I personally have yet to find a headphone that cannot sound better with some EQ, and the OAE1 is no different. But I also like to have a collection of headphones with different sound profiles, and because of this I feel the OAE1 is a good headphone for people to add to their collection, even though they may only like it with certain recordings.

Conclusion

The Grell Audio OAE1 represents a bold reimagining of what headphone listening can be. By positioning drivers in front of rather than over your ears, Axel Grell has created a product that attempts to bridge the gap between speaker and headphone listening in a way few other products have attempted.

For listeners who primarily enjoy speakers or for those who are building a collection of interesting (i.e., different) sounding headphones, the OAE1 offers a compelling option. Its speaker-like Free Field derived soundstage, unique tonal balance, and open-ear design make it uniquely suited to those seeking a different kind of personal audio experience.

While its unconventional approach has generated controversy among traditional headphone enthusiasts, this misses the point. The OAE1 isn’t trying to be a better version of existing headphones. It is offering an entirely different approach to personal audio that suggests that the listener should “think different” about their audio experience, but if they do, they will be rewarded with something uniquely interesting.