Headphone Reviews

IEMs, whether custom or universal in nature, are often used by on-the-go listeners. Their portability and high sensitivity make them ideal for use with smartphones, while the more revealing models benefit from DAPs and even dedicated portable amplifiers. As previously mentioned, I use my old 64 Audio V3 in this capacity on a regular basis. But I confess I almost never leave the house with the A18t.

For my sensibilities, it really isn't a good candidate for portable use. I don't feel comfortable taking such an expensive IEM out and about where it can be lost, stolen, or damaged. I also don't really think portable use is the proper context to showcase the quality of a flagship model anyway. Surely an entry-level or mid-range choice would give a convincing enough performance, with background noise and general distractions, I doubt I'd be taking full advantage of what the highest models have to offer.

Despite that, I began my evaluation by pretending I was that sort of user, but without actually leaving the house. I initially listened via the excellent Astell&Kern KANN player, then switched to the almost ubiquitous Fiio X5 mkIII, then the compact Cayin N5ii, and finally Sony's now-outdated yet oh-so-enjoyable NW-ZX2. Swapping between these four players – all quite competent in their own unique ways – allowed me to get a good handle on the sonic character offered by the A18t.

A quick note before I continue: all of the following impressions involve the M15 Apex modules installed. I do have the M20 modules and appreciate the variation they bring to the sound, but for my tastes the M15 is clearly superior. To completely oversimplify – the M20 increases bass response at the expense of both treble extension and openness, which to my thinking is not desirable. I'm sure some people will love the warmer M20 sound though, and it really is great to have options.

Listening

The A18t comes across as exceedingly well balanced. The first line of my listening notes reads "neutral, but not boring, highly dynamic, with incredible extension". Many, many hours later, I have not deviated from that initial summary. I could almost stop there, but I won't, as it doesn't quite capture the full experience. If you're pressed for time though, that little blurb will do the job.

The first thing that stands out to me is the superb low-end clarity. The A18t digs deep, providing authoritative sub-bass extension. I also sense a tasteful bit of extra energy in the mid-bass region, just enough to liven things up and keep them from being dry or sterile, but not so much that it crowds the midrange. The result is a textured, nuanced reproduction of low frequencies which, for my tastes, strikes an arguably perfect balance between quality and quantity.

Listening to "Tricotism" from the XRCD release of Unity by Ernie Watts, I can very clearly delineate the duelling electric and upright acoustic bass guitars. Beyond that, each has a convincingly genuine tonal heft which, in my experience, is not so easy for balanced armature transducers to capture.

I am also struck by how coherent the presentation is. With a mind-boggling 18 drivers per side, it must be exceedingly difficult to pull this off. I've heard models with a mere three or four drivers have trouble blending each section together. Telltale signs include smearing, disjointed transitions between frequencies, and an overall sense of "confusion" to the sound. In contrast, the A18t might as well have a single full-range driver in each side. I hear nothing but precision tuning from top to bottom, with zero detectable overlap or signs of a hand-off from one driver-array to the next. This is precision crossover design at its finest.

Not to be outdone, midrange is impressively clear and transparent. Vocals come through as clean and articulate, violas have lifelike fullness, and trumpets have a fantastic sense of bite. "Purity" is the word that comes to mind, backed by a sense of openness shared only by a select few transducers (of any type). The A18t lets one hear deeply into the heart of the recording... and for that matter, the playback chain, as I'll discuss more in depth shortly. While it does reward higher-end system, the A18t can also sound relatively satisfying even from a basic smartphone. This is not a trailer-queen IEM.

Let's talk treble. Perhaps the highest point of the A18t presentation. Clarity and extension are brilliant in a way very few IEMs can match. I'll branch out and add full-size headphones to that claim, as well as speakers while I'm at it. Obviously these all have their own unique presentation but to my ears, the A18t belongs to a tiny and highly exclusive club. Other members I've met include the JansZen Valentina Active speakers, certain Stax electrostatic ear-speakers, and to a lesser extent, the Focal Utopia headphones and Usher Dancer Mini One DMD speakers. In contrast, many exceedingly expensive speakers and headphones do not quite make the cut in this area. Audeze LCD-4? Nope. Wilson Sabrina? Not even close. My beloved Empire Ears Zeus XR? Getting closer, but not quite there. Even speakers I adore such as the Vivdi K1, Marten Django XL, and YG Acoustics Carmel - all quite expensive and very highly regarded – do not perform up to this high standard in the treble region.

The result is absolute precision and tangibility, even when playing difficult material. Challenging piano tracks sound utterly convincing – the A18t unravels Hiromi Uehara's complex piano runs with complete poise. Or, to be more specific, about as well as the associated playback chain will allow. Listening to "Haze" from the SACD release of Hiromi's Voice (ripped to DSD via the time-consuming PS3 method), I hear the Cayin and (even more so) the Sony devices outplay their otherwise enjoyable counterparts. This is a very challenging track, and the A18t pulls it off when fed by the right hardware – stunning attack, beautiful decay, layer upon layer of intricacies that you only pick up on after repeated listening sessions. And it gets even better when I switch to my home system.

Listening At Home

A word of warning before I go any further: the A18t is relatively difficult to drive with home gear. Obviously it doesn't require big power like certain low-efficiency planar magnetic headphones. Quite the opposite, actually – sensitivity is rated at 116dB/mW, so just about any headphone output in existence will have plenty of juice.

The issues are hiss, volume control, and the impedance dipping to nine ohms at 1kHz. Hiss is a common problem when using a big headphone amp to drive an in-ear monitor. Some are worse than others, and it isn't always predictable based on the specs alone. The A18t is what I'd call worse than average in this regard, though certainly not as bad as some others in my collection. Still, it will disqualify plenty of amps. The other associated problem is usable volume control. These things get so loud, so quickly, that many amps simply become unusable. Lastly, a low output impedance is essential. Something like a five-ohm OI can do a fine job with certain IEMs, and can sometimes end up actually enhancing the sound with certain models. But in this case you really want to go as low as possible – definitely under two ohms, with one being ideal. If not, bloated mid-bass and a funky, uneven midrange become readily apparent.

With that in mind, I settled on two different systems, a "real world" setup, and then a slightly crazy rig. The more sanely priced system involved a Rupert Neve RNHP headphone amplifier ($499 USD) being fed from a Cayin iDAC-6 ($699 USD). The admittedly over-the-top system used a Pass Labs HPA-1 ($3,499 USD) paired with the Wyred4Sound 10th Anniversary Limited Edition DAC ($4,499 USD). Both systems were leashed via USB to my Euphony PTS music server with outboard Keces P8 linear power supply, playing everything from lossless Tidal to quad-rate DSD.

In both systems, the result was appreciably richer and more detailed than what I heard from the portable players. The Cayin/Neve duo imparted a thicker, more liquid presentation, particularly in the midrange. The Wyred/Pass rig was more resolving, with superior dynamics and more precise imaging. The A18t really lets you know the quality of your upstream gear. The latter setup was used for the following comparisons.

Comparisons

RE2000

As far as I can remember, the $2,000 USD HiFiMAN RE2000 is the most expensive universal IEM I've heard. I got a reasonably comfortable fit with several different tips, and settled on SpinFits as the optimal choice for my ears. Using a universal IEM again reminded me why I love custom models so much – despite achieving a seemingly great fit, I could only handle the RE2000 for about 45 minutes before things became uncomfortable enough to disrupt my listening session.

In terms of sound, the A18t is in another league. The RE2000 has a somewhat brighter tilt, but when you focus on that treble it becomes clear that 64 Audio's contender unravels more detail, and does so with a smoother, more natural feel. The RE2000 is actually fairly impressive in isolation, but is simply outclassed in this comparison.

The rest of the spectrum ends up being a similar story. The HiFiMAN has good kick down low but can't muster the same authority as the A18t. The 64 Audio CIEM has cleaner vocals which project forward into space more believably than the RE2000. The A18t also sounds more "out of head," while the RE2000 is adequate but nothing special in this regard.

In the end, it's really no contest at all. I acknowledge the $1,000 USD price discrepancy here, but there simply aren't many competitors to choose from in this lofty price bracket. I was actually surprised that the RE2000 is a very competent performer. It's one of the best sounding universal IEMs out there right now – yet it totally falls flat compared to the A18t.

UERR

The Ultimate Ears Reference Remastered, or UERR for short, is an excellent custom IEM selling for $999 USD. I prefer it to the RE2000 despite the price difference. Due to its popularity and relative affordability, I consider it something of a benchmark in this space. The A18t costs three times as much and sports six times as many drivers per side. A fair comparison? Not really, but as I said, it's a benchmark.

The A18t sounds substantially more punchy and full-bodied than the UERR. While both models could genuinely be described as relatively neutral, the A18t better fits that term thanks to its effortless extension at both ends of the frequency spectrum. In comparison, the UERR comes off as somewhat dark and overly smoothed, like an older Sennheiser HD650 with the infamous "Veil." It's a pleasant sound, to be sure, but the A18t really digs deeper into the music.

In comparison, the UERR sounds "small," lacking in both dynamics and low-frequency extension. It's like trying to use a quality mini-monitor in a room that's just too large. The A18t is a large tower speaker with a superb crossover, which retains excellent driver integration but provides all the dynamic gusto one could ever need.

Zeus XR Adel

A quick comparison to the Zeus XR Adel must be made, as it remains a well-known reference, and the price – within a couple hundred dollars of the A18t – makes it an obvious choice for comparisons.

The key difference I hear is that the Zeus has a more "meaty" midrange presentation. Vocals, particularly of the male variety, come across with more lushness and body. The entire midrange seems a bit forward in the mix, whilst the A18t is flatter and more tonally neutral. Now, when I say the word flat, some readers might (understandably) take that to mean lacking in excitement or tonal density. Not so. The A18t is wonderfully rich, but also very tastefully balanced. In comparison, the Zeus has a bit of romantic coloration, which may or may not be desirable.

64 Audio U18t

One last quick comparison I have to mention is actually the 64 Audio U18t; a universal version of the same product. Now, I've heard universal IEMs which sound identical to their custom-molded counterparts, and I've also heard some which sound significantly different. The U18t was the latter. I probably tried a dozen tips in my quest to make this work but in the end I couldn't do it.

The whole thing had a weird tonality to it. Midbass was a tad bloated, while the thunderous sub-bass I so enjoy from the A18t seemed softer, less convincing. Midrange seemed vaguely recessed, while those spectacular highs had a bit too much emphasis to them. I also heard several troublesome peaks in the upper mids and treble which I do not hear on my custom-molded version.

I think the universal shell used by 64 Audio is very well made, and I generally got a comfortable fit with most tips, so I'm at a loss to explain why the U18t sounded so inferior to its custom sibling. This could have been a fluke – with such a complex design, there are many opportunities to mix something up. Perhaps something was wired out of phase on the U18t I tried... I really can't say for sure. In any case, I just didn't find the example I tried to be representative of what the A18t is really capable of.

Conclusion

By now, I'm sure you can tell that I'm totally blown away by the performance of this custom IEM. It is, without a doubt, the most resolving, transparent IEM I've ever heard and I've heard most of them. If you enjoy a generally neutral, explosively-fast presentation with superb separation and layering, this is as good as it gets from an in-ear monitor. I can point to competitors tuned with specific colorations which might be preferable in certain situations, but for all-around use, this is easily the best IEM I have ever heard.

My bottom line: the 64 Audio A18t is truly a world class performer. In a field of headphone competitors with similar or even higher price tags – Focal Utopia, HiFiMAN HE-1000, Audyssey LCD-4, JPS Labs Abyss, Stax SR-009, etc, the A18t acquits itself very well, performing at, or very near the top of the class in each sonic category. I realize custom in-ear monitors and full-size headphones are different animals, but to my ears the A18t is actually the best of this prestigious bunch. No question about it.

Should this CIEM realistically be on your wish list? For most, the sane answer is "probably not."

But am I glad it exists? Absolutely. For a select few die-hard audio enthusiasts, the 64 Audio A18t is a game changer.