Earproof Atom custom IEM

General Information

Custom dual driver IEM with a soft silicone shell, small form factor that just goes in the canal.

Latest reviews

Pros: Nice clean neutral "reference" type sound, very comfortable and low profile, relatively low priced
Cons: Oddly difficult to drive, if not driven well they sound sterile and thin, Earproof website doesn't have them listed yet

I think it is safe to say that the headphone market is on an upward swing. Headphones are no longer relegated to being niche products, but have become far more mainstream than ever before. We are seeing growth in all categories, ranging from budget models to celebrity endorsed overpriced gear, and even very expensive flagship products. In ear monitors have kept up with their full sized brethren in terms of having more brands making good products than we’ve ever seen. As a subsection of the IEM category, custom molded IEMs have arguably had the most growth of all.
Go back a little ways and read some old threads on HeadFi – you won’t find many discussing customs, and when you do it seemed to be limited to upscale folks who already had pricey Stax or other rigs. I’d say very few average music fans were actually interested or even aware of customs back then – and for good reason: most of them came in at $600-800 or more. Frankly, as someone who owned some of those early models, I don’t know if the sound quality was there in comparison to similarly priced full sized models.  But these days things are different. Instead of a handful of choices, we have well over a dozen custom IEM companies to choose from.
There are a few different types of custom companies out there. Some of them have been around for a long time, such as Westone or Ultimate Ears, and are well known all over the world. Others are newer such as Unique Melody and Heir Audio, but are aggressively trying to expand worldwide with their excellent offerings. But there is another type, which is actually more common than you might think: the small time company who is not really interested in becoming a worldwide player. Instead, they are content to serve their local market, often doing so for many years without any recognition outside of their home region.
One such company is Earproof. Based in the Netherlands, Earproof has been making custom products for monitoring as well as hearing protection for about 8 years now. They attend many events such as concerts and festivals, and have a big focus on raising awareness about potential hearing loss caused by excessive volume in these types of venues. They offer a wide range of earplugs and monitoring products for musicians as well as security/law enforcement, news media, and others. Despite all of this, I had never heard mention of them on HeadFi. So I decided to contact them to see if they were interested in changing that.
Peter Van Galen is the man in charge at Earproof. After some discussion, he told me to send in my ear impressions, and he’d come up with something. A short time later I received a non-descript package in the mail. A handwritten note from Peter said something to the effect of “These use the smallest drivers on the market. They won’t get super loud, but I hope you enjoy them. –Peter”. Accompanying the note was a pair of custom molded IEMs – in white silicone, with a very small form factor, the product was called the Earproof T3i. It sounded remarkably clean and clear in an Etymotic ER4S sort of way, but unfortunately one side had some type of driver damage, producing distortion at nearly all volume levels. Back to Earproof they went, with Peter promising to find the problem and fix it.
That was just the beginning of what ended up being roughly 7 months of waiting. It seems that Peter had an idea for a new design, and he wanted to perfect the sound before sending it out. I waited patiently, and a few months ago a package arrived again. Though externally identical to the T3i, this new product sounded even better than the previous incarnation. Peter finally gave me the details – the new design is called the Earproof Atom. It uses the dual driver version of the tiny balanced armature driver used in the T3i, for a much more full range sound delivery. The price was set at $469. I was excited to give it a listen, and I’ve been using it almost daily for a while now.

As you can tell from the pictures, the Atom is a very small format custom IEM. It inserts in the canal portion of the ear, and is hardly noticeable from most angles. The shell is made from an extremely soft silicone – I can bend the canal portion back to the base in a U shape if I wanted to. This makes for a very comfortable fit, and probably the best seal I’ve ever encountered from a custom IEM. Isolation is very good, though I suspect a small amount is lost due to the “canal only” type design. Sounds can still resonate through the remaining portions of the ear which the Earproof Atom leaves bare.
As is nearly always the case with silicone shell custom IEMs, the Atom has a non-detachable cable. Peter advised me that he was unhappy with the current solution due to issues with microphonics, so the cable on my pair will not be the final design. I do find the cable slightly prone to tangling, and the microphonics are worse than the standard Westone-style braided cable. So if Earproof has a better cable in mind than this Kevlar-reinforced design, then it can only be a good thing. That said, this cable is certainly not bad. It protrudes in an upward fashion so it is clearly meant to be worn over the ears. In retrospect kind of I wish I had asked for mine to exit at the bottom to be worn straight down, though I don’t even know if that is an option.
Inside, the Atom is based around a Sonion 4400 dual balanced armature driver. This is a tiny thing - even smaller than the popular TWFK dual driver unit from Knowles Acoustics which is used by many IEMs of both the universal and custom variety. Sonion was heavily involved in tweaking the overall design to achieve optimal results. Nominal impedance is 70 ohms and sensitivity is 105dB. As I’ll discuss later, these specs are misleading – this is one tough IEM to drive to full potential.
In terms of colors and designs, the Atom is offered in clear or white. I got white. Mine have the red Earproof logo on the right side and a blue logo on the left side. I assume this is standard though you could probably request to leave them blank. There isn’t much room for a fancy design so I doubt Earproof lets you submit your own artwork, but I never specifically asked.



Despite having more custom IEMs than I care to count right now, this is actually my first full silicone model. I’ve had the Westone ES3X with the tips made of vinyl but that was nowhere near as pliable as these. I don’t know how to really gauge quality in a case like this, other than to say that the shell is completely smooth, appears well made, and fits perfectly. The cable (again not the final production version) is sturdy and seems like it would last forever. It has no memory wire for keeping the loop around my ears, but I found that cinching the cable after the Y-split to be somewhat snug to my neck keeps it perfectly in place no matter what I do. So overall I’d say build quality is quite good from my limited experience. I think the white color is well done; the “clear” silicone customs I’ve seen always appear cloudy compared to a good acrylic shell. I think that’s just a property of the material, and doesn’t say anything about the build quality, but that doesn’t mean I have to enjoy it. So I’m pleased with the white.




Apologies for the blur, here is the flexibility I mentioned. 
Since this wasn’t a retail package, I didn’t get much in the way of accessories. The IEMs themselves, a semi-hard shell storage case, and a printout of the frequency response chart. A person ordering these might get a whole lot more, or might just get the same kit, I’m not sure.

Here is the equipment I used to evaluate the Earproof Atom:
Portable: Sansa Clip+, Sansa Fuze, QLS QA350, hiSound RoCoo D Power Edition, TCG T-Box amp, Audinst AMP-HP
Home Sources: Squeezebox Touch, JF Digital HDM-03S music server, Pioneer Elite N-50 network player
DACs: Anedio D1, Yulong D100, Violectric V800, Yulong D18, Matrix Quattro, Kao Audio UD2C-HP
Amps: Yulong A100, Violectric V200, Analog Design Labs Svetlana 2, Matrix M-Stage
Music was a variety of genres, almost always in FLAC format ranging from 16-bit/44.1kHz to 24-bit/192kHz and everything in between. Cables are all by Signal Cable, with power conditioning by Furman. The Atoms were burned in for well over 100 hours prior to serious use and by now have quite a few more hours on them.
Here is a size comparison between the Atom and a regular sized custom:



My initial experience with the Earproof T3i was interesting. It sounded very fast and clean, with surprising low frequency extension for a single driver balanced armature design. But it was limited in dynamics and suffered from some unfortunate harshness in the upper regions, which I don’t believe was related to the faulty driver issue. Given the price that I thinkEarproof was asking for them (the website is confusing), and the loss during conversion to US dollars, I could not imagine recommending them considering how strong the competition is in this segment. But the Atom is a whole different story. It has twice the drivers, which helps address the shortcomings of the T3i, and it sells for under $500 USD. Now we’re talking.
Even though this is a dual driver design, it is still billed as the world’s smallest dual driver. So I was expecting something fast, detailed, clear and extended in the treble, but still lacking in overall resolution and weight. I was surprised to discover that not to be the case. The Atom can unexpectedly kick you in the pants when the music calls for it - with the right amplification. The more I listened, the more I started hearing traces of some of my favorite full sized headphones. Some HD600, some W1000, a bit of K701… yet overall the Atom has a unique sound that can’t be summed up with just a single “sounds like” comparison. But allow me to explain further.
Once again – with the right amplification, the Atom has rich, deep, fast bass capabilities. On quantity it is roughly in line with a well driven HD600, meaning a bit more present than the K701. In terms of quality, it is right up there as well, though I perceive slightly more sub-bass impact with the Atom than either of those full sized models. That might just be the effect of pressurization from a sealed ear canal, rather than the open full sized models, but I appreciated it.
The speed and attack of the bass is just startling – I enjoyed listening to some of my favorite punk bands like Dogwood, Lagwagon, and NOFX, with the Atoms easily keeping up with the fast paced double bass drum action. The downside is that it really prefers good recordings, which is not really the usual description of this genre. Some of my albums sounded thinner than others, but the better ones sounded really great.
With bass heavy music, the Atoms provide a nice impact in a sort of “reference” way, but they don’t quite rattle your skull. They do better at “punch” than “rumble”. In this way they remind me of the Sennheiser HD800. Everything that should be there is there, beautifully and faithfully recreated. The textures are rich, and you can really distinguish one sound from another. Yet there are times when you wish for some more “oomph”; a more realistic portrayal of actual air being displaced by a big woofer. The Atom (and the HD800 for that matter) doesn’t quite do that in the way that something like the Heir Audio 8.A can do, or even a budget model like the Westone AC2. But the Atom is more accurate and quick in the bass than the AC2, so it is a bit of a tradeoff.
Mids strike a nice balance – not forward, not recessed. It would be easy for them to be on the prominent side in relation to those quick, tight lows, but Earproof does a fantastic job of keeping them neutral without making them too dry or boring. Vocals of all types sound very well done, though again better recordings really shine. I spent a lot of time listening to Nancy Bryan’s debut album “Lay Me Down”. I have the CD in the JVC XRCD format and I’ve always thought it sounded amazing. But I recently discovered a hi-res release in 24/96 from HDtracks. Her voice is stunning on tracks like “Blood Song” and “In and Out of Time”, and I believe the hi-res version clearly shows its superiority. Not all headphones are capable of resolving that distinction but the Earproof Atom apparently is.
I appreciate the lack of graininess in the upper mids and highs. While not quite electrostatic smooth, the Atom is one of the smoother IEMs I’ve heard at any price, while still remaining detailed. Even the classic Etymotic Research ER4 models have a bit of grain standing between you and the music. The Atom is virtually grain free.
Highs are crisp and well extended.  There is almost a complete lack of sibilance here, which again highlights the balance achieved. Some IEMs try pushing too much detail, resulting in sibilance ruining the fun. Others go too far in the name of smoothness and omit some details, meaning it doesn’t quite sound like a real person there in front of you performing. The Atom has just enough crispness to let you hear those subtleties without over blowing them, turning them into the musical main event. They don’t quite have the same sparkle as something like a UM Miracle, but they would only seem lacking with direct comparisons. On their own I never felt them lacking.
Soundstage is potentially a weak point here. Not that it is bad per se, but it is on the smaller side compared to some of the similarly priced competition. Instrument placement is very accurate, and it seems the focus is placed on defining the performance space rather than making it huge. This is in line with the general presentation that these give, which is closer to a nearfield studio monitor than a hi-fi speaker setup. I call it a weak point because I know some people prefer the bigger presentation, though personally I find that the Earproof approach “works” just the way it should.
I made it a point to talk about “quality amplification” during the above comments. Though all the custom IEMs I’ve heard have shown some benefit from a better source and amplification, the Atom is in another category – it seemingly requires something better than your average DAP. Maybe it is the 70 ohm impedance that causes most players to stumble, but I didn’t enjoy it much from a Sansa Fuze or Clip+. I could go to maximum volume and it would just barely be loud enough, or almost loud enough depending on the music. In most cases with other IEMs, full volume on a Sansa will blow out my ears. So despite their tiny size and low driver count, the Atom is up there with some of the most advanced 6 and 8 driver models I’ve heard in terms of system matching.
On the go, I liked it most from the hiSound RoCoo D Power Edition, which is normally supposed to do best with headphones rather than IEMs. I also liked it with an iPod 5g running Rockbox, using an LOD and a portable amp such as the Audinst AMP-HP. But the real fun began when I tried it with my bigger home equipment. IEMs with a big tube amp? Not usually, but in this case, absolutely! My single ended triode amp from Analog Design Labs sounded fantastic with the Atom, giving it enough refinement to be up there with much more expensive models. It also sounded wonderful with my high-powered Violectric V200 amp, maintaining a silent black background despite the several watts per channel on tap. Even something as simple as the built in headphone amp on my Grant Fidelity TubeDAC-11 was a huge step up from the portable experience with a standard DAP. I’m not quite sure how I feel about this. On one hand, I’m a big proponent of traveling light and not using a portable amp when possible. The Atom is not my first choice in that scenario. On the other hand, I really appreciate how high it scales on better equipment. In that respect it goes much farther than a dual driver model has a right to go, and the results are very impressive.

Here is the frequency response chart as provided by Earproof. It indicates a clear, detailed sound with good extension on the low end, a bump centered around 3.5 kHz, followed by a sloping roll-off to 10kHz. From there it picks back up with some good response to around 15kHz, then a final roll-off from there on up. The general shape of the chart is not so different from Tyll’s uncompensated measurements of the Etymotic ER4 and the Phonak PFE112.
I was a bit concerned about the THD measurements in the lowest frequency range under 40Hz or so. Overall levels are low with that exception. I browsed Tyll’s measurements and found that it isn’t too far off the norm compared to other armature based designs. The Grado GR8 for example is higher across the entire board, though it comes at higher playback levels too. Ultimately this supports my listening impressions that the Atom is not meant to be played extremely loud. Given the level of isolation it offers, I don’t find this to be an issue.
Competing products would generally be any custom IEMs in the sub-$500 range. I’ve got a few of those handy for direct comparison.
Westone AC2: These two couldn’t be more different. Though both have dual drivers, the AC2 has a massive driver dedicated to low frequency reproduction and a smaller unit for highs. The Westone has plentiful bass – some may find it overbearing. It is fairly high quality but the Atom has the edge in terms of tightness and control. AC2 has more distant mids, and sharper highs. The Atom is more articulate, more neutral, and cleaner in terms of grain and sibilance. The AC2 has a much larger soundstage. The AC2 is very easy to power, though benefits from smoother sources.
1964-Ears 1964T: This time we have a triple driver model against the dual driver Atom. The 1964T is fairly neutral, with a slightly tipped up bass region and a bit of a downward tilt on the highs for a warm relaxed feel overall. With two very large bass drivers, the 1964T is capable of bigger bass than the Atom, though again I think the Atom has a slight edge in bass clarity and speed. The Atom has a more crisp presentation with everything being right there in front of you, but not overly aggressive. The 1964T handles music in a more easy-going manner. Once again the Atom is more difficult to drive.
In general I believe there is a pattern here: the Earproof Atom is very competitive in its price category. It takes significantly more power to “wake up” than its rivals, and may seem a bit uninspiring until you properly drive it. Once given a good source and amplification, it scales higher than the rest, and is potentially the best lower-mid range product out there (assuming the neutral clean sound is what you are interested in). I’m finding it an indispensible tool to use while reviewing amps and DACs because it gives such a clear window into the sound, like a junior in-ear version of a Sennheiser HD800. When using a Sansa Clip I find the Westone and 1964 Ears models superior, but when used with an amp the Atom takes a clear lead.
From all the descriptions I’ve heard by people I trust, the Ultimate Ears Reference Monitor seems like it has a sound signature close to the Atom. I haven’t heard the UERM so I can’t confirm the similarities, but all the reviews I’ve read of that product basically sound like they are describing the Earproof model. I’m not implying that they are equals – the UERM has three drivers and sells for twice the price. Logic says it should be better (though I’m not exactly sure how much better) but I have no way of knowing until I hear the UE model for myself. But for someone interested in that type of sound yet finds the $1,000 price a bit steep, the Earproof Atom could be a good alternative.
I don’t see an update about the Atom on the Earproof website at this point. So I’m not really sure what the status is. But I hope this ends up being a commercial product that can be enjoyed by more people than just me, because it absolutely deserves to be heard. The sound is about as neutral and clean as I’ve heard from a custom IEM, yet it manages to keep me engaged rather than bored. The form factor is very comfortable, and the soft silicone ensures a perfect seal. It really is an excellent user experience all the way around.
The difficulty I see is that it doesn’t reach its full potential with a standard portable DAP or phone. Many people like to travel light, and you’d think these tiny customs would be perfectly matched with something like a Sansa Clip+. But using them in that fashion does not give you the full picture of what they are capable of. I’m not just talking about the last bit of refinement either – they actually sound boring and lifeless in many cases. But plug them in to a portable amp, or better yet a home system, and they really take flight. The result is something like what you’d get running a quality near-field studio monitor. It may not have a massive soundstage, and is obviously limited in low frequency output, but nonetheless can sound breathtaking with good recordings. If that sounds like what you are looking for in a custom IEM, I encourage you to contact Earproof about the Atom.
Very well written review. Interesting product.
Great review as always, a pleasure to read.


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