This is like taking candy from kids it is insanely easy to drive on just about every portable format I have. Some of that is down to the ADEL technology allowing it to sound louder at lower volumes but it’s also a very efficient earphone at 16ohms and 117db. It’s one of the few earphones I have that the stock volume memory setting on the Glove A1 amp is a bit too loud. Roughly 4-6 steps down on the Glove A1 makes it just about right for long-term listening.



It has no issues either jacking straight out of all the DAPs I tried including the DX90, FiiO X3/5, Lotoo Paw Gold and the Shozy Alien. Interestingly I was expecting a ton of noise and hiss with the Alien but it stayed much lower than I expected. It’s not noise free, DAPs such as the Paw Gold and the DX90 have a much lower noise level but in full swing, it sounded gloriously natural and full with the Alien.

Matching wise the Paw Gold had excellent detail and control with a slightly warm tilt to the signature with the ADEL A12 whereas the revised X5 went slightly in the opposite direction with a much more neutral flavor albeit slightly less resolving. I enjoyed the micro gain control on the DX90 which is up there with the Paw Gold for volume adjustments and something I highly recommend for the highly sensitive A12.

Quiet Amps

Though you can survive without them, portable amps added some interesting characteristics when paired with the A12. Just do not go too far up in the impedance and power equation as noise tends to creep in rather quickly.


It goes without saying both the RX from ALO Audio and the Picollo from Cypher Labs had no problems coping with the A12 high-efficiency levels with my preference this time veering to the RX’s bigger soundstage and dynamics over the smoother fuller Piccolo. The added power of the Picollo is not really needed here.

Glove A1/Duet

The CEntrance Glove A1 paired with the AK120 had great noise levels with a nice smooth if slightly soft signature. Cypher Labs’s cracking Duet analog amp tightened things up a little over the smoother Glove A1 and sounded very comfortable on low or mid gain with no noticeable noise issues.


JDS Labs 02

Even the budget 02 matched very well with the A12 sounding clean, and clear on challenging vocals such as Agnes Obel’s Philharmonics though slightly lacking in the fullness and dynamics of the other two more resolving amps.

Noisier Amps

Sometimes too easy to drive is limiting also and some great amps lost out due to high levels of noise or lack of gain control with the ADEL A12. I won’t go into the Theorem 720 this time, it’s not a CIEM friendly amp at this level of sensitivity and I have delved into it so many times its starting to feel like Groundhog Day. Suffice to say it has noise.

Bakoon HP-01M

The dynamics and extension on the voltage out of the Bakoon HP-01M were incredible (once you get past the chronic imbalance at low volume levels) but sadly the power on this portable powerhouse was a bit too much and noise levels were disturbingly high during quieter listening sessions.

Sony PHA-1

Another one to have slight noise issues was the Sony PHA-1 though not by quite a wide a margin as the Bakoon but it was still noticeable when paired with the DX90 on high gain. The Sony does not have the strongest analog section to it but on low-gain line out with the DX90 it had no issues driving the ADEL A12.

So long as you do not push the Sony past noon on the gain pot the noise will not be noticeable. Oh and avoid the awful pop on the PHA-1 by plugging in your A12 after you turn it on, it’s rather jarring.


Vision Ears VE6X (20ohms, 122db)

Setup: Glove A1/AK120

Right from the get-go the VE6X needs about 25-30% more volume than the A12 to sound optimal. Now whether or not that is an efficiency issue or the ADEL tech I can’t say with certainty but it could be cited as evidence that the claims are true.

Tonally the A12 is quite a different beast to the VE6X. Both are excellent in detail retrieval but the A12 has a far more weighted and forward bass response that is not quite as nimble and tight as the VE6X but for me has slightly better texture and detail. There is no midbass tuning on the A12, it’s not all slam and no depth, this is a very refined and extended bass response. The VE6X bass is tighter, faster, but leaner and not as extended with less impact.

The VE6X is a bit flatter and more neutral than the A12 which tends to sound warm to neutral and slightly more forgiving overall. Both have an excellent treble extension but the VE6X has a slightly more forward treble that can just sound a bit sharper or clinical than the A12’s treble response which sounds smoother and a bit laid back in comparison.

The soundstage of the VE6X is vast and wide, almost HD800 wide which the A12 can’t really complete with width wise. Depth wise the A12 is better extended than the VE6X but doesn’t hit the same heights as the treble of the VE6X.

Both are great, both have different tunings with different audiences. If you want orchestral, choir, operatics and some soundtracks or acoustics then the VE6X is quite hard to beat. If you want something for a modern rock arena, a dance hall or a mosh pit where weight and crunch are more desirable then the A12 delivers with aplomb.

1964EARS V8 (loaded with Twag v2) (18ohms, 117db)

Setup: Glove A1/AK120

Still one of the best midbass slamming CIEM I have in the collection and the proverbial bass head monster. Volume wise it sits closer to the A12, perhaps about 10-15% more on gain than the A12 using the same rig and adding weight to the ADEL claim.

Tonally the A12 is much more 3 dimensional, with far superior texturing and micro detail than the V8. The vastness of the sub-bass response compared to the V8 is significant and whilst you can still smile brightly with the slam from the V8 it really does sound more closed in and intimate.

The A12 also pulls away from the V8 with a far cleaner and present midrange and a vocal presence that makes the V8 equivalent sound slightly dull and lacking in resolution. Both have a smooth and slightly laid back treble response but the A12 has the greater extension and detail with far better articulation. The V8 in comparison sounds far less dynamic and one dimensional in comparison.

Given the V8 is half the price or less it’s perhaps unsurprising and I would still highly recommend the V8 as one of the best sub-$1k bass head CIEMs but if you want a far more immersive and detailed bass response with more accurate timbre then the A12 is the clear winner.


UM Merlins (12 ohms, 108db)

Setup: Lotoo Paw Gold

My first custom and the one that convinced me I didn’t need to get an LCD-2 to have some sort of LCD-2 (pre-Fazor) type experience with its huge sub bass, relaxed mids, and treble that still carried enough detail to sound engaging and pleasurable. This is a hybrid single dynamic 4 BA setup with a single bass port for the dynamic bass driver.

Once again the A12 is about 25% louder than the Merlin at the same setting so now I am starting to get rather convinced by the ADEL tech stuffed into this CIEM.

Tonally the A12 is a lot cleaner and snappier than the more languid and slower Merlin. There is a heap more energy in the mids and treble of the A12 making the Merlin sound a bit veiled and lifeless in comparison. Whilst the Merlin always had good detail the A12 adds more zip and sparkle in all areas to give a far more engaging and musical experience. The Merlin also comes off as a bit warmer than the A12 which lies somewhere in-between warm and neutral by comparison.

Both have excellent sub bass extension but the Merlin dynamic driver doesn’t feel as impactful and a bit soft in comparison to the A12’s more visceral low-end response. Texture and detail of the A12’s bass response are also that bit better than the Merlin.

Whilst the A12 treble is slightly softer and more laid back than the VE6X it is leaps and bounds ahead of the Merlin’s more shelved down treble experience. Both are forgiving but the greater detail and articulation of the A12’s treble response is far more convincing. Soundstage is big on the Merlin but the A12 is equally big and more precise, layering and imaging on the A12 has better spaci4g and is far more accurate.

Once again though there is a considerable price difference and it is 12 BA drivers versus 4 BA and one dynamic but it does show how a modern BA CIEM can easily outperform dynamic drivers if given half a chance.

Custom Art Harmony 8 (Non-Pro) (50ohms, 107db)

Setup: Ibasso DX90 / ALO Audio RX

The Harmony 8 looks beautiful, is neigh on almost perfect for comfort and seal, second only perhaps to the M-Fidelity SA-43 by a tiny margin. The A12 has about 98% the Harmony 8’s seal but the silicone of the Harmony 8 silicone shell material has a clear edge in terms of comfort in the ear as well as sliding in and out. That’s the advantage of silicone right there in a nutshell (or should that be silicone shell?).

The Harmony 8 though is also one of my most inefficient customs with a high impedance and low sensitivity of 50ohm and 107db. It sounds good on a DAP but much better on an amp, particularly the RX during my review. It also has a great set of mids, a big vocal presence, a weighted but pacy and tight bass response, and a relaxed but detailed treble experience. Soundstage also is big but not as tall as some other CIEMs with a better treble response.

By contrast, the A12 is more balanced than the Harmony 8 with a far airier and bigger sound, a more 3-dimensional soundstage with greater space and a more forward treble that has a bit of sparkle compared to the Harmony 8 pro. It is also way more efficient even in generic like for like tech comparison on paper but even more so with the ADEL technology.

On the RX and DX90 combo, the Harmony 8 sounded properly driven at 220 on the DX90 and around noon or 1pm on the RX volume pot. The A12 needed only around 10am on the volume pot of the RX in comparison to sound properly driven and what an experience it was out of the RX. Cleaner, faster, wonderful decay and control and a very deep and musical bass response with the superior body to the Harmony 8.

Treble on the A12 sailed past the performance of the Harmony 8 with way more headroom, air and detail. The Harmony 8 has great vocals also, big vocals in fact and whilst the A12 didn’t have quite the big vocal experience the detail and texture in the vocal presence was way more refined. Timbre also just felt a bit more natural and accurate with the A12 over the slightly warmer and thicker Harmony 8.

Rhines Stage 5 (24ohms, 120db)

Setup: Ibasso DX90

Both the ADEL A12 and the Stage 5 by Rhines are neck and neck in high quality, mature and subtle designs. Efficiency wise the Stage 5 is also one of my more ‘go lightly’ custom units sitting at 20ohms and 120db. The Rhines is a 5 driver BA design which has a slight but elegantly tuned v curve signature. It’s dark but neutral with a weighted but excellent and well extended bass response and a smooth but very well extended treble signature. The mids are a bit back in the mix with a slightly weaker vocal presence compared to say the Harmony 8 big set of pipes.

Right out of the jack the Stage 5 was driven with confidence at around 190 steps in the DX90 volume control but the ADEL A12 sounded equally confident at the same volume but a little bit fuller sounding. To be terribly honest there was not that much separating the two loudness wise with the A12 having an equivalent loudness of around 186 on the DX90.

Compared to the Stage 5, the A12 has a slightly leaner sound but still warm to neutral sounding. In fact, the Stage 5 makes the A12 relatively bright sounding in comparison but in a good way. The dynamics and energy of the A12 sound more engaging with a better balance in the mids than the v shape of the Stage 5. The Stage 5 has good detail but the A12 more forward and refined midrange and treble response sounds more convincing and engaging. Both are actually quite excellent in detail retrieval to be fair but that greater level of clarity and balance came from the A12.

JH Harvey Roxanne (15ohms, 119db)

Setup: Ibasso DX90 / ALO Audio RX

The Roxanne, in theory, should be ever so slightly more efficient on paper at 15ohms and 119db as opposed to the ADEL A12’s 16ohms and 117db ratings. This is the universal version as opposed to the custom so for seal and comfort, no contest the ADEL A12 is smaller, way better sealing and far more comfortable. The Roxanne is huge but thankfully my ears can handle it and they seal pretty good, about 80% good compared to the A12.

This time the difference in volume was far less noticeable. In fact, it was barely negligible with both driven comfortably around 186 on the DX90. If I had to pick a winner it would be the A12 though by a very tiny margin. Both were equally loud but the A12 has a slightly fuller and more energetic sound than the Roxanne at the same level. That is nitpicking and to be honest I was half expecting that to be the case given the hypersensitivity of the Roxanne.

The Roxanne at stock bass setting has a bit less bass extension and weight than the A12 but has a slightly thicker and warmer tonality overall than the warm to neutral A12. Detail is excellent on both but the A12 just shades it for me for bass definition, speed, and texture. Treble on the Roxanne is a little bit more forward and brighter than the slightly smoother and more laid back A12 but both sound articulate and extended.

Of course, you can increase the bass significantly with the Roxanne bass adjuster but it tends to crowd out the rest of the range a bit too much for me personally and it loses some of that balance and sparkle when full on compared to the A12.

Final Thoughts

The objective here by 64 Audio was to deliver a flagship CIEM utilizing technology that basically would prevent us from significant hearing loss in the long run over the competition yet sound awesome. Two things happened in my mind to achieve this. First, the ADEL technology to reduce the effects or pneumatic sound pressure and in effect offer a bigger sound at lower volumes. And second, a really efficient low impedance design to effectively sound good on any setup you throw at it. You could argue a flagship that sounded great is the most important pitch of all.

I cannot scientifically prove to you that the ADEL A12 tech works but here is what I can tell you right now. After testing with no less than 5 competing CIEMs of excellent quality including the Harmony 8 Stage5, V8, UM Merlin, and the awesome VE6X, I can safely say that the ADEL A12 sounded the most complete at the lowest volume. There were varying degrees of gain difference between the A12 and the other CIEMs that could be attributed to differing levels of sensitivity; after all at 16ohms and 117db, the A12 is already a very efficient CIEM compared to say the Harmony 8 at 50 ohms. However, even with the R0xanne at 120db the A12 had a very slight edge.

Of course, this is not all about volume. Do not buy this thinking it will always suck up less juice. It does sound great out of just about any source I threw at it but certain amps brought out a little bit more flavor and character such as the Duet that further optimized the natural sound of the A12.

In the end, it has to sound good for the price or the technology is just a curiosity. Luckily the A12 sounds good, neigh great and is the perfect musical antidote to the HD800 like qualities of the VE6X. Do you want something with fantastic bass extension, detail, and weight with super smooth treble and a balanced midrange with beautifully controlled vocals? That’s the A12. Want a deep, 3-dimensional soundstage? That’s the A12. Want something that just exudes a natural flowing tonality with no unnerving peaks? That’s the A12.

For those who want a sharper top end or a tighter faster lower end with an immense soundstage then the VE6X comes highly recommended as the classical, operatic and possible the acoustics genre CIEM of choice. Both sit perfectly happy side by side. Yes, the price is always a barrier and the A12 does not come cheap but it is competitive to the likes of the Roxanne’s and the Visions Ears of this world so if you are in the market with this kind of budget then you can’t ignore the A12’s pedigree.

A12 Technical Specifications

  • Fit: Custom. Made from provided ear impressions
  • Transducer type: Twelve precision balanced armature drivers
  • Transducer configuration: 4-low, 4-mid, 4-high
  • Impedance: 16 Ohms
  • Sensitivity: +/- 117dB SPL @ 1mW
  • Freq. Response: 10Hz – 20 kHz
  • Noise Isolation: Adjustable via ADEL™ module
  • Cord Length: 48 or 64 inches
  • Warranty: 2-year Parts and Labor

17 Responses

  1. Matthew Quinn

    How is the isolation in comparison to other CIEMs? I have read some reviews saying it is not up to par because of the ADEL module. Do you agree?

    • headfonics

      Isolation will vary depending on your impressions and fit but outside of that I thought it was excellent – the modules I have not had a chance to compare given this one came with the stock plastic one.

  2. Clarence

    since the adel 12 is so efficient and easy to drive, do you think the mojo which is on my shopping list, is too much for adel 12 to handle.

  3. wasaki

    From your memory : which one let you enjoy the music more roxanne or adel 12?
    which one has bigger soundstage ,better imaging and sound fuller ?

    • headfonics

      Adel A12 overall for me, it has a nice full sound and the treble is just dialed back ever so slightly to make is a very pleasurable listen. Bear in mind though my Roxanne is the universal variant.

      • Coll. IEm

        I just bought roxanne ,did you think adel 12 and roxanne in the same level ?
        if the treble laid back you mean it sound darker in Adel 12 ,
        if the trble is bright why owners of rox. say it dark not bright or natural ?

        will you consider roxanne one of the TOTAL iem ? I’m not searching for refrance sound cause most of them is boring .is that true ?
        sorry I asked you many questions .

      • headfonics

        I think both are excellent performers but tonally I have a preference to what the A12 can do and I think the Vision Ears VE6 does what the Roxanne can do only better. Its aso huge in your ear for the amount of drivers given the A12 is much smaller and has more drivers.

        You can tune the Roxanne a little so rather than bright vs dark I would say what you are hearing is bass forward or neutral depending on where you hear the dial. In compairson to the A12 the treble on the Roxy is brighter.

        Best reference sound is the VE V6XC.

  4. PG

    Thanks for the great review
    I have a question
    I listen to R&B, indie, folk, pop and hiphop sometimes jazz
    I am considering between k10 and a12
    which one would fit me better?

    • headfonics

      I have not heard the K10 but the A12 is ideally suited to a lot of those genres.

  5. Lazar Ranisavljevic

    I’ve enjoyed reading many of your reviews, especially the CIEM ones. Having studied the ones that interest me most (A12, K10 and VE6 X), I feel that there is a reason that you’ve omitted any comparisons to the K10. I am in search for a main headphone that must be a CIEM (and cannot afford multiple pairs) and I would appreciate a three way comparison as that would greatly aid my decision.

    Kind Regards

    • headfonics

      Thank you for your kind compliments and we will certaily have more customs reviews before Xmas for you to continue to enjoy.

      Actually the reason why the K10 has not been part of the compairson is simply due to the fact Mike reviewed the K10 and I reviewed the other CIEMs. Mike is approx 10k miles away from me and its a custom so its unlikely we can ever do direct comparisons with the K10.

      Its one of the perils of multiple staff writers I guess.

      • Lazar Ranisavljevic

        I look forward to reading more quality reviews.

        In case i decide to rush my purchase, do you think I would be best served by VE6 X if my listening focus is classical (think Rachmaninoff, Mozart, Mussorgsky,..), and jazz & blues as secondary (think John Lee Hooker, Howlin’ Wolf, Louis Armstrong,..) or would you recommend some of the competition? (I am from Serbia, so I have no possibility of actually hearing any of the great CIEMs, hence my decision will be only review-based)

      • headfonics

        The VE6X is excellent for classical to be honest with its big and wide soundstage and slightly more strident treble range but if you want something slightly thicker with a heavy bass then the A12 will be a nice option especially with some blues. Tough choice but I would give the nod for the VE6X for your preferred taste.

      • Lazar Ranisavljevic

        You’ve just confirmed what I’ve been leaning towards- the VE6X is the one if I can digest the relatively sharp treble. I love the freedom that sound stage gives, and I love the air and details which can provide intimacy at the same time. Additionally Vision Ears are in Europe so I can get them personally and avoid paying customs and tax (30% combined) and reclaim VAT so they would be cheaper than any flagship from the US (the A12 would probably be upwards of 2700 USD) or the far east. Besides, what is a better excuse for a visit to Berlin.

        Thank you for your time and insight. Your help is greatly appreciated!


      • headfonics

        Sounds like a plan :) I personally do nto find the treble sharp on the VE6X it just seems brighter with a slightly harder edge than the A12 which is more laid back. I think that is a better tonal fit though for classics.

        VE is in Koln also – maybe you can go there and they will do the impressions when you visit Belin and save on any potential mishaps with 3rd party impressions.

      • Lazar Ranisavljevic

        So essentially not harsh but extra detailed- just the way I like my sound :). However, I will probably have to order them before coming to Germany because I can’t afford staying there for weeks until they build them… Unless I can ask as a special favour to get the impressions say Monday and be done by Friday. You just gave me an idea, no harm in asking.

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