General Information


Driver Type/Count
Eighteen precision balanced armature drivers

Driver Configuration

1 tia high, 1 high-mid, 8 mid, 8 low

Frequency Response

10Hz – 20kHz


106 dB/mW @ 1kHz @ 1mW (84mV)


8Ω Nominal


Integrated 4-way passive crossover


-20dB w/ m20 module, -15dB w/ m15 module,
-10db w/ mX module


Latest reviews


Headphoneus Supremus
64 Audio U18s
Pros: Contrasting Tia tuning
Warm, soothing tonality
Detailed yet relaxed
Top notch clarity
Amazing BA bass
Mid tuning is velvety
Treble is not over extended but offers air
Great layering
Much better stock cable
Cons: No DD bass some crave
Soundstage isn't huge, but it's layered well to avoid claustrophobia
Some may prefer typical Tia treble

Get yours from Bloom Audio

From 64 Audio:

64 Audio revolutionized the IEM industry in 2016 with its world class reference level U18t, the world's first 18-driver earphone. Now, with the introduction of U18s, 64 Audio has taken the heritage of the 18 driver platform and further pushed the envelope of innovation in sound and design. U18s combines proprietary drivers, LID technology and a new electronic crossover network to deliver a uniquely exceptional listening experience.

U18s is handcrafted in the USA from aerospace-grade aluminum billet. CNC milled, hand blasted, fly cut, and twice anodized - the result is a striking fractal design that is inspired by nature itself

  • Tia:

The tia system is comprised of three major elements: open balanced armature tia drivers, the tia single-bore design, and tia acoustic chambers. The Trio features two major elements of the tia system: the tia driver and the tia single-bore design.”

  1. Tia Driver:
“An open balanced armature speaker design for realistic resolution and transparency. By opening a balanced armature, the diaphragm becomes fully unobstructed, reducing resonance in the IEM and allowing sound to travel more naturally to the ear.”

  1. Tia Single Bore:
“A huge advancement in eliminating unwanted tube resonance. The large bore itself serves as a sound-shaping chamber and aids the tia high driver in delivering a linear and coherent frequency response. The short sound path provides remarkable high-frequency extension and smoothness. The large single bore also allows for easier maintenance”

  • Apex:

“Apex, or Air Pressure Exchange, is a pneumatically interactive vent that releases air pressure from a sealed ear canal. It comes in two variations, m15 (-15dB) and m20 (-20dB).”

  1. Alleviate Listener Fatigue
“When you seal a miniature speaker in an ear canal, the air inside becomes trapped. Apex relieves this air pressure, allowing the eardrum to move naturally, so you can comfortably listen longer.”

  1. Extend The Soundstage
“Freely moving air extends the soundstage and provides a more natural listening experience. It also preserves bass frequencies and helps the listener distinguish individual instruments.”

  1. Hear Your Audience
“Custom in-ear monitors provide amazing isolation and help you hear your mix more clearly and at lower volumes than a wedge monitor or earbuds. Apex lowers decibel levels while preserving the clarity of the sounds around you, so artists on stage can connect with their audience while protecting their hearing.”

  • LID:

“LID, or Linear Impedance Design, enables a consistent, reliable sound regardless of what source. This proprietary circuit corrects the non-linear impedances of the drivers, restoring proper interaction with the source and preserving the desired sound signature.”

“Whether you’re a musician plugging into a variety of gear at different gigs or studios, or an audiophile listening from low-impedance sources, LID ensures your IEMs are delivering the desired sound signature consistently.”

“And like all our IEMs, this model can be used with a wide range of personal audio devices as well as all hard-wired and wireless monitor systems.”

  • U18s Specifications:

  • Driver Type/Count: Eighteen precision balanced armature drivers
  • Driver Configuration: 1 tia high, 1 high-mid, 8 mid, 8 low
  • Frequency Response: 10Hz – 20kHz
  • Sensitivity: 106 dB/mW @ 1kHz @ 1mW (84mV)
  • Impedance: 8Ω Nominal
  • Crossover: Integrated 4-way passive crossover
  • Isolation: -20dB w/ m20 module, -15dB w/ m15 module,
  • -10db w/ mX module



  1. U18s Universal In-Ear Monitors
  2. TrueFidelity Eartips (S,M,L)
  3. Silicone Eartips (S,M,L)
  4. SpinFit Eartips
  5. Ear Tip Holder
  6. 8-Braid Silver Cable
  7. Branded m20 apex Modules
  8. Branded m15 apex Modules
  9. Branded mX apex Modules
  10. Round Sticker

  • The Sound:

(All analysis was done using the M15 Apex module.)

One constant you’ll most likely see referenced in the audiophile realm is the ‘lack’ of sheer depth and wallop regarding balanced armature bass. While I often agree dynamic drivers out-class balanced armatures in bass output and resolution, this is as close as it’s ever come for me. The U18s has deep bass with dynamic driver like decay, whilst adding a bit more texture than run of the mill dynamic drivers. Obviously thanks to the nature of the balanced armatures 64 Audio crammed in here. This lends a helping hand to create dynamic driver like rumble while retaining much of the balanced armature bass speed, tightness. Even a true basshead can appreciate the bass delivery here in the U18s. This bass extends well into the 20-30hz region and juts off in the other direction far enough to add some warmth to the lower mid-range. It does so without causing any bloating or bleed over. Mid bass offers enough punch to prevent drums and bass guitar plucks from sounding lifeless or flat. It’s not Legend X bass here but it’s healthy sounding for sure.

Mids: As I stated in my Trio review, “One thing I have noticed about many 64 Audio offerings is that they know how to tune the mid-range”. Welp… the story remains the same here. The U18s has a soothing and warm mid tuning, from the lower to upper. They achieved this all while maintaining exceptional vocal clarity for both male and female vocalists. Instruments are also rewarded from this boost. Certain string instruments or piano may not be as vivid but they certainly do not lose an ounce of resolution. Another interesting thing I enjoyed was, unlike most 64 Audio flagships, there is no, “illusion” here to make the stage seem expanded. The U18s doesn’t have any of those unusual dips or tuning anomalies to emphasize stage. Despite this, there is sufficient separation in layering present while allowing vocal ranges to sit up front or slightly back from front; not recessed. Typically, these tuning dips referenced earlier make the vocalist and other mid bearing instrumentation seem distant, sometimes behind other frequencies. While this is nice for the grand presentation of headspace, 64 Audio has already done that with the Trio, Fourte and Fourte Noir. I applaud the decision to keep the U18s a pure example of their technical prowess in proprietary technology. Of course, there is tuning going on here, but it’s devoid of tricks; reliant upon only a reference-y take on things. It really is lovely to hear. You’re afforded the warmth but maintain the resolution with zero compromises in an intimate presentation.

Treble: Very simply put, the U18s has a soft and warm tilted treble presence. Don’t get it twisted though, there are times those Tia drivers will jump out and shine. The U18s doesn’t throw down the etched and crispy treble often thought of when referencing 64 Audio and Tia. That being said… good, I’m glad. Once again, they already offer that in the likes of U12t, U18t, Trio, Fourte and the elusive Fourte Noir. Albeit a different treble tuning, I don’t find it lacking whatsoever. It doesn’t beg for your attention at all, but it also isn’t absent in the overall presentation. I find it highly resolving, properly weighted-yet relaxed. You really can’t ask for a more coherent treble output to match the overall temperature of the tuning. If it was brighter, it would stand out too much and seem disjointed. If it was warmer, it would pull the overall tuning into the veiled territory. There is a natural softness or airiness to the top end as well which allows it to remain separate from the lushness in the bass and lower mids. Thankfully, the balance is just right.

  • Overall Sound Presentation:

The 64 Audio U18s has more of a warm reference signature than dull analytical one. I wouldn’t call the stage enormous but there is enough by way of imaging and separation to avoid congestion. Bass is decently elevated without being distracting or disappointing. Mid-range has room to breathe and flex some clarity in vocal presence and instrument separation. Treble greets you with macrodynamics so good, the hell with the microdynamics. Cymbal splashes for example are finessed sounding while they deliver the all the detail needed to know you’re absorbing top notch sound. You can just as easily fall asleep with the U18s in your ears as you can use them for a relaxing critical listen.

  • Comparisons:

(All comparisons done using M11 PRO, Lotoo Paw S1 and DX300)

  • 64 Audio u12t (M20):

Twister6 isn't the only one with a granite countertop! :wink:

The critically acclaimed U12t, yet sometimes described as ‘boring’ but hard to fault is no slouch in any regard. I feel that many who praise the U12t sound will appreciate the U18s but gravitate towards the U12t more, due to its more resolute, reference tuning. Bass is similar but a tad weightier sounding in the U18s. Mids are also heavier or more colored where the U18s is concerned. Treble is more on the crisp side with the U12t whereas it is softer in the U18s. They are both great, this ultimately will just come down to tuning preference. Unfortunately, I have never heard the U18t to offer a comparison.

  • 64 Audio Nio (M15):

The bass seems a bit more forward and boomy on the Nio from sub bass carrying into mid bass regions. Bass is most definitely much more resolving and controlled with the U18s, although less present. Mid-range is more wet sounding with Nio and cleaner sounding with U18s. Treble is similarly tuned, but I find the U18s to deliver it in a more profound and effortless way. The Nio has a little more energy in some 6-8k regions but it sounds thinner to me. If you cannot afford the entry cost of the U18s, the Nio would get you much of the way there for less. With the M20 module, the Nio just introduced a lot of compression and overall is too thick for my liking.

  • Empire Ears Legend X:

As I have said before, the Legend X has the best quality bass on any IEM known to date. The quantity, decay, texture, power, depth… the list goes on. As an obvious biased advocate of Legend X bass, I cannot fault the U18s bass or say it disappoints. I actually quite like it. Mids are similar in weight but the U18s does nudge the clarity a bit here, while the Legend X nudges the thicc’ness. Vocals seem slightly further back when compared to the U18s, but not much. Treble is also very similar in how it is perceived, maybe being just a tad ‘livelier’ with more bite on the Legend X. I often laugh at how much of a chameleon the Legend X is and how often it upsets other IEM’s when you least expect it. The U18s is a formidable opponent here though. If you want the Legend X sound with less bass and slightly more forward and less thick vocals, alas the U18s. The treble is too close to sway one way or another. The Legend X also presents a noticeably larger sound stage with greater separation and imaging.

  • Campfire Audio Solaris OG/SE:

In simple terms, the U18s is a more engaging and colored Solaris with a less holographic soundstage. Bass hands down goes to the U18s. Mids offers a similar clarity with slightly more detail available in the U18s. Treble is more relaxed in the U18s and splashier while more elevated on the Solaris. That being said, for the going rate of the now discontinued original Solaris and Solaris SE, they are hard to argue with.

  • Noble Sultan:

Price is the only thing similar here. The U18s is just, to me, a better all arounder. Where the U18s injects a warm, pleasant effortlessness, the Sultan just hulk smashes, and it overwhelms the frequency range. It’s just an unforgiving density that rolls into an uninspiring thin, glassy sounding treble range. I don’t have much good to say about the Sultan and maybe it was the fit, seal or whatever but yea, wasn’t impressed. Then again, I don’t know of a Noble IEM that I have heard to date that I enjoy. Maybe it’s the ergonomics. The U18s on the other hand, did impress me in pretty much every way.

  • Empire Ears Odin:

My precious Odin... this was a hard one. As much as I, “all hail Odin”, I was actually appreciative of the tuning differences between the Odin and U18s. The Odin just throws this detailed, vividly clear and holographically layered sound over some amazing deep and well controlled bass, right at you. It commands your attention. The U18s manages to accomplish a good bit of detail while softening the projection. Odin bass is more linear and sub bass focused. It’s world class bass, seriously. The U18s bass is more elevated into the mid bass region which adds a nice warmth whereas Odin prioritizes the mid bass and lower mid region for obscene clarity and neutrality. Upper mids aren’t all that different. The Odin has more energy and clarity in this region but the U18s is one of the very few, if only monitors I have been able to A/B against Odin and not feel are veiled. The treble is where I feel the Odin achieves a more natural timbre and life like presentation. I’d be remiss if I did not summarize how these titans present soundstage. Simply put, the Odin presents a much larger, more separated sound. A friend of mine, Takao, nailed this perfectly… If you created a U18s with the width and dynamics of the Odin, you would surpass almost all monitors to date.

  • Conclusion:

The 64 Audio U18s is a welcome addition to the typical Tia tuning. It offers a warm velvety high-definition tuning that rarely disappoints and often lets one bask in the musicality. You can listen to them critically or just get lost in your favorite acoustic, vocal or high energy mix. Although it doesn’t possess the large holographic soundstage, it does offer a smooth, layered presentation that allows it to remain separated. Lastly, hats off to 64 Audio for really stepping up their stock cable game. The included silver cable is fantastic in all regards.

Awesome review. Do you believe that the lack of a large holographic soundstage on the U18s can be fixed with a different source?
I don’t believe so. I am pretty certain that is the presentation they are going for. As I mentioned in my review, the separation and detail lends well to keeping things layered enough to avoid congestion. This creates a decent stage but when compared to titans like Odin, Fourte and Traillii, it’s not on their level. It’s still probably my favorite 64 Audio IEM though.
Thanks for the review.


twister6 Reviews
Headphoneus Supremus
The Warm Side of the Moon!
Pros: powerful bass impact (depending on module selection), fuller body warm analog tonality, clear detailed sound, new faceplate design, interchangeable apex module, LID tech, updated set of accessories.
Cons: price, not a typical tia-driven treble, the tuning is quite different from U18t if you expect 18s to be a variation of original.

The product was provided to me free of charge for the review purpose in exchange for my honest opinion. The review was originally posted on my site, and now I would like to share it with my readers on Head-fi.

Manufacturer website: 64 Audio. Available for sale directly, as well as various retailers like Audio46.


A month ago, 64 Audio announced 3 new 2021 products, teasing us with eye candy computer-generated images, and the rumor mill went into overdrive! In the past, 64 Audio used to spoil us with more frequent new releases, then after U12t, Tia, and N8 things slowed down a bit. Noir was a refined version of Fourte, and Nio was a logical universal step up from N8. Then, a year ago, A18s was announced and the pandemic hell broke loose. Unfortunately, lack of CanJams and other audio shows and custom-only nature of the design are kryptonite factors in audiophile world. Plus, “s” denoted studio version of this 18-driver flagship which could be misunderstood.

Similar to N8, it looked like A18s CIEM release was targeted more toward stage and studio musicians rather than consumer audiophiles. Yes, it felt like N8 déjà vu all over again, and I was afraid it will follow the same footsteps of us waiting 2 years for a proper universal version. But as many probably aware, 64 Audio makes uni demos of their Custom-only IEMs for audio shows and retailer stores. Those are not for sale, even so quite a few people in 64 Audio thread on Head-fi expressed their wishful thinking for one, even willing to buy store demos. Thus, demand was definitely there, and to my surprise 64 Audio responded swiftly with a new design supply.

Just to clarify one thing, I did receive the original custom A18s a few months ago, and quickly realized it wasn’t for my ears. Due to sharp first bend of my left earcanal, CIEM nozzles usually end up being super short which affects the tuning, especially when dealing with tia driver at the tip of the nozzle. When I requested uni demo of A18s and then compared it to U18s review unit, I was able to hear a noticeable difference to reconfirm my original suspicion. Now, with a proper universal U18s in my ears, I’m ready to share my impressions.


Unboxing and Accessories.

U18s arrived in a similar large size packaging as U18t and Fourte/Noir models. The removable sleeve has 3D like image of the shells with a focus on a new faceplate pattern and branded apex module. This was also the first 64 Audio product I received with a new logo which I think is very clever. The 6 and 4 are now interlocking where the number “4” extends into letter “A” while going through number “6”.


On the back of the sleeve, you have a zoomed in view of the shell design and every component inside of it. It is very interesting to see a compact shell, housing 18 BA drivers, including tia in the nozzle and also apex module. I was surprised a spec wasn’t printed, but there were highlights of the design with “apex”, “tia”, “LID”, TrueFidelity (foam eartips), and SpinFit (eartips) mentioning.


Inside under the magnetic cover you will find an inspirational message from Vitaliy Belonozhko, the founder and chief sound designer of 64 Audio. In the main storage area of the box things look totally updated in comparison to previous releases with a similar packaging. You have two round cutouts in a foam block, holding top and the bottom of the leather storage case. No more custom pelican-like case, those are used now with CIEMs intended for musicians who require a more secure storage. Universal IEM packaging is designed to appeal to consumers, and U18s features the same round leather storage case included with Nio.


The lid of a storage case features new updated “64” logo and was placed at the top of the box with a plastic eartips holder. The holder gives you a clear view and easy access to 3 types of included eartips, a set of wide-bore opening black silicone tips (S/M/L), a set of TrueFidelity foam eartips (S/M/L), and a set of SpinFit brand name eartips (S/M/L). That was a welcome addition to accessories. The bottom part of the leather case was holding a foam insert with U18s securely sitting inside, and a plastic holder for 3 sets of apex modules, MX and M20 in a holder and M15 in U18s shells already.

I noticed right away that 64 logo was printed on the top of apex module; surprised it took 64 Audio that long to finally brand their apex modules with a logo which looks great! Of course, foam insert is only to hold the shells without a cable attached, and it could be easily removed to use leather storage case which has plenty of room for U18s with cable attached and apex modules holder and even a few spare eartips. A sticker with a new 64 Audio logo was included as well.



64 Audio stock cable uses ultra-low resistance flexible non-microphonic silver-plated copper (SPC) wires which come in either Professional or Premium versions. Sometimes it creates a confusion because people see different cable plugs/connectors in pictures without realizing it is still same wires. The main difference between these cables is in hardware where Pro version has a more basic 2pin connector mold which is compatible with recessed and non-recessed socket, red/blue indicator for sides id, and a plastic 3.5mm angled plug.

Premium cable uses the same wires, has a higher quality hardware with non-recessed angled 2pin sturdy connector and L/R letter indicator, memory wire, 64 Audio branded plastic y-split and a plastic chin-slider, and uses a premium quality brand name plug with options for 2.5mm, 3.5mm, and 4.4mm termination. These cables come standards with universal models, such as Fourte/Trio/U18t/U12t/Nio, and look more “premium”.

U18s comes with a New 8-braid Premium cable they refer to as “Silver”, but it actually uses Pure Silver Plated OFC wires, each with 65 strands of 44awg conductor, just a little bit thicker than original Premium wires. It is a very low impedance cable, 0.28ohm of total impedance. Despite 8 wires instead of a typical 4, the cable is still very pliable, relatively lightweight, and non-microphonic.


During Nio launch, 64 Audio also introduced a Premium Silver Hybrid cable. While this new cable is called Silver Premium, in reality it has a Silver alloy core surrounded by 200 Silver-Plated Copper strands. Basically, this is 26 AWG gauge ultra-low resistance 4-wire multi-core structure Silver plated OCC and Silver Alloy. It even uses a premium audio grade solder to make sure signal path is pure and has low resistance. So, this is not a pure silver cable but rather a hybrid of Silver and SPC material. This design was chosen to reduce the wire resistance without making the gauge thicker or doubling the number of conductors (from 4 wires to 8 wires).

It is a very nice-looking cable, very soft and flexible, non-microphonic, braided between plug and y-split, with all the same hardware as 64 Audio Premium cable, including non-recessed 2pin angled connector mold, memory wire (which I personally can’t stand and removed right away), 64 Audio branded y-split, plastic chin slider, and the termination plug of your choice, depending on availability. The cable is optional and cost extra. I will cover how it sounds in comparison to Premium SPC cable further in my review.


The U18s shell follows a traditional 64 Audio design shape, but to my surprise it was a little taller than U18t. In theory the have the same number of drivers, the same apex cavity, and tia driver in the nozzle. LID tech was added and maybe internal design and driver placement was optimized that resulted in a slightly taller shell, but it was still very comfortable to wear and had a very durable build with a shell machined from a solid piece of aluminum and all black matte stealth finish. It also features a non-recessed universal 2pin socket and a matching metal nozzle with a mesh at the tip to keep elements away from tia driver.

But what really stands out here is an all-new faceplate design. You will not find a traditional 64 Audio faceplate with an inlay insert like in previous releases of U18t, Fourte/Noir, U12t/Trio, and Nio. U18s features all metal faceplate with a cool 3D fractured pattern and sort of a dark gunmetal finish. And this pattern looks truly 3D, achieved with a shinier top surface and black filled pattern cavities. I tried to capture it in pictures, but pictures don’t do it justice. The faceplate look is enhanced further with a branded apex module.


Inside the shell you have all BA design featuring 18 drivers with a 4-way passive crossover partitioning 8 lows, 8 mids, 1 high-mid, and 1 tia high drivers. Balanced Armatures (BA) are typically self-enclosed with a single opening port, while you can think of tia as an open BA driver where one of the enclosure walls is removed, to enable direct-radiating of the inner diaphragm which no longer has a 4-wall confinement. Tia driver is usually positioned in the nozzle, next to the grill since it has to be closer to your earcanal. As a result, U18s doesn't have sound tube bores going to the nozzle, and instead has a mesh cover to protect from wax build up.

Another tech included with U18s, that wasn’t previously available in original U18t, is their Linear Impedance Design (LID) crossover where despite a low impedance (8ohm), U18s should be compatible and have the same signature when paired up with different sources, regardless of their output impedance. Of course, the tonality of the source will affect the pair up synergy and the sound you hear, but variation in output impedance is no longer a variable in U18s design.

And I’m sure by now everybody is familiar with 64 Audio apex (Air Pressure Exchange) modules, but just in case if you have been living under a rock, it is the interchangeable venting system that releases air pressure sealed in the ear canal for fatigue free listening. The included apex modules have a fixed sound isolation, based on the model number: MX (-10dB, black module), M15 (-15db, dark grey module), and M20 (-20dB, aluminum color module)


As I mentioned in the intro, I did receive A18s CIEM at first, and if you decide to take that route, especially if you prefer custom fit or want to customize the look of your IEM, 64 Audio has a very comprehensive tool to design your monitors. The one in my original CIEM had a transparent shell with an exotic wooden faceplate, and I decided to include pictures of it here in the review so people can appreciate the layout and placement of all these drivers inside of a compact shell.


The fit.


Sound Analysis.

I analyzed U18s sound performance paired up with LPGT while playing a variety of test tracks, such as Agnes Obel “The curse”, Sandro Cavazza “So much better” (Avicii remix), C-Bool “Never go away”, Ed Sheeran “Shape of you”, Alan Walker “Darkside”, Galantis “Hunter”, Iggy Azalea “Black widow”, Indila “Boite en argent”, Dua Lipa “Love again”, Counting Crows “Big yellow taxi”, David Elias “Vision of her”, and Michael Jackson “Dirty Diana”. By force of habit, I let U18s play for about 4 days in a loop before I started analyzing the sound. I used stock SpinFit eartips and stock cable in my analysis.

U18s has a fuller body warmer detailed tonality. The sound is smooth, natural, and quite detailed, not revealing like in U18t but rather clear and detailed in upper mids and treble. The lower frequency range has a fuller body with a warmer tonality and surprisingly good bass impact for BA drivers. But you have to pay close attention to which apex module you are using because they leave a noticeable effect on tonality and signature. In most of the 64 Audio IEMs with removable apex I prefer to use M15 because it has the perfect balance between bass impact and soundstage expansion, keeping in mind "15" referring to 15dB isolation. However, when I started to listen to U18s with a default M15 module, I found a lack of definition in lower mids.

As expected, going between MX, M15, and M20 changes the soundstage expansion, with MX and M15 being wider due to less isolation and M20 being narrower. But in terms of tonality, upper mids and treble sounded quite similar, while bass and lower mids did change. MX gave bass a more neutral quantity, making signature more balanced, with more focus on natural detailed mids and natural clear treble. Not your typical tia airy sparkle, but instead, a smoother well-defined treble. Moving up to M15, bass gained impact and rumble, but the decay of bass notes extended and blended in with lower mids. It wasn't bleeding into mids, but rather blending in a way that caused bass to lose its articulation and definition.

Then, I decided to switch to M20 and had a Eureka! moment. I did notice a trade-off with soundstage width shrinking down a bit. It was still above average but less expanded in comparison to MX and M15 modules. The sub-bass was as deep and had the same amount of rumble, maybe even a little more than when compared to M15. Mid-bass punch was stronger and faster, not basshead overwhelmingly strong, but just enough to tilt the scale of balanced sound sig into a slightly L-shaped territory. But the biggest benefit was a better separation of bass from lower mids. With M20 I hear the decay of bass notes to be shorter, giving bass more control and better definition. And with that, lower mids gained more clarity.

Now, with all this said, I still consider overall sound signature to be balanced (W-shape) because regardless of the bass impact it comes through with a noticeable quantity of deep velvety sub-bass rumble and punchy mid-bass impact, mids/vocals are not recessed, despite being natural, organic, and better than expected layered, and treble is well defined, clear, and actually extended without being too bright, crisp, or too airy.

I hear the overall soundstage to be above average, and as already mentioned, it gets wider with MX and M15 modules. But still, you get more depth/height rather than width when analyzing U18s. Typically, I find positioning and imaging of sounds to be better when tonality is more revealing. Don't get me wrong, I don't find anything wrong with accuracy of instruments and vocals placement when listening to U18s. But it was easier to pin-point sounds in less busy and more instrumental tracks while got a little more complicated in busy multi-layered tracks where I had to focus harder to zero in on some instruments. I do want to add, this was relative to M20 module, while switching to MX gave instruments and vocals more room to breathe. It was easier to pin point everything, but I was missing bass impact with MX, a trade-off you have to keep in mind.

In more details, bass is very responsive to apex module selection and I think many will prefer to go either with MX or M20, or maybe I'm just projecting my own preference. MX will give you a neutral bass impact, you can still hear the rumble and the punch, but the impact scaled down. M20 gives you a nice authorative slam, not an overwhelming basshead level but enough to cut through any serious EDM track with a strong rhythm. When you are listening to less aggressive music with natural instruments and no kick drums, bass comes into play with a deeper rumble to give instruments more natural fuller body tonality. And as I mentioned before, I found stronger impact with M20 to give bass more control and better articulation.

Mids and treble are natural, smooth, detailed, balanced, never falling behind the bass even with M20 module. You get a better definition and more forward presentation with MX module which puts more focus on mids. With M20 presentation of mids is less forward but still with enough focus. Mids/vocals are clear and natural, there is some layering, not as much as you would hear in more revealing tuning like U18t, but still enough to appreciate the expansion of vertical dynamics where the sound never felt compressed. Treble is clear and detailed, not crisp or sparkly but extended and with a natural airiness.


Eartips selection.

The selection of eartips is crucial to any universal in-ear monitors and will affect the sound, especially the bass impact depending on the seal. Due to a large opening of my earcanals, I usually go for the largest size eartips to get a better seal. Also, please keep in mind, eartips impressions are subjective and will be based on anatomy of your ears. Here, I was analyzing the sound using LPGT, M20 module, and stock cable.

SpinFit (stock, baseline) - deep bass impact, natural clear vocals, smooth detailed treble.

Silicone (stock) - more bass impact, smoother mids/treble, mids are slightly recessed.

TrueFidelity Foams (stock) - more neutral bass, more forward mids/vocals, even smoother treble.

Final Type-E - a touch less bass impact with mids/vocals being slightly more forward, and treble being just a little brighter. Good alternative if you want to make sounds a little more revealing.

AZLA Xelastec - similar to SpinFit but with a little more bass impact and rumble, and bass having more authority.

Symbio F - similar to Type-E where mids/vocals are being a little more forward, but the bass impact remained the same as with stock SpinFit.


Cable pair up.

I’m aware that some people don’t believe in cables and have very strong opinion about it. It’s not my intent to change those minds. Instead, I’m just sharing what I hear during my testing. What makes sense to me, a metal wire is a material with physical properties of resistivity, conductivity, purity, and unique geometry, all of which put together act as a filter between your source and headphones. Variations of these physical properties can affect the conductivity of analog signal, resulting in a sound change, from a subtle to a more noticeable level. If the talk about cables upsets you, please skip this section. Otherwise, enjoy these short impressions.

w/64audio Premium Silver hybrid - signature is W-shaped/balanced with enhancement of lows (more control, better articulation, faster), mids (more revealing), and treble (more sparkle).

w/Eletech Iliad - puts a little more emphasis on bass and treble, feels like tia drivers gain back some of their lost sparkle, but overall, it also makes the sound slightly U-shape due to perception of mids/vocals being a little behind.

w/EA Leo II octa - signature is W-shaped/balanced with enhancement of lows (more control, faster), mids (more revealing), and treble (more sparkle), very similar to 64audio premium silver cable.

w/PlusSound PPH8 - not much changes related to a sound sig, but I do hear more sub-bass rumble, mids remaining the same, being smooth and natural, and treble gaining some sparkle. Soundstage did expand a little more.

w/PWA 1960 4w - puts more emphasis on bass where I hear more sub-bass rumble and mid-bass impact, mids/vocals remain the same, maybe just a touch more revealing, and treble has more sparkle.



The comparison was done using U18s with a stock cable, SpinFit stock eartips, M20 (unless noted otherwise), and LPGT source; volume matched in every comparison.

U18s vs A18s

Custom 18s just didn't work out for my ears. As I have mentioned already, my left ear has a sharp first bend and as a result custom nozzle is usually trimmed down to look almost like universal, and right earpiece nozzle has to be short to match the left one. With some iems it works, but not with all of them. Doesn't mean U18s and A18s were tuned differently. It just means that custom shell with a very short nozzle skews the intended sound tuning where to my ears A18s treble was not as extended and upper bass and lower mids got thicker, giving the sound more body and some bloat, taking away from clarity and making vocals sound off. But when I got universal demo of A18s and later received the final U18s, their sound was nearly identical which makes me believe that U18s and A18s with an adequate nozzle will sound the same as well. And U18s will give you another level of sound tuning through tip rolling.

U18s vs U12t

The first big difference that stands out here is the treble with 18s being smoother and more organic while 12t being crisp and sparkly, more air and better extension. In theory they should have the same tia driver, but it is tuned completely different. Next, as you shift your focus to mids, you hear brighter vocals with neutral lower mids body, making vocals more revealing and thinner, while 18s has a lot more body with vocals sounding thicker and warmer. Using M20 module, 12t actually has a surprisingly deep sub-bass rumble and good mid-bass impact, though scaled down in quantity and with bass having shorter decay, thus lower mids being more neutral.

U18s vs U18t

This is a very interesting comparison because I'm sure people will expect a lot of similarities, while in reality there are more differences. Regardless of the module you use, tia driven treble is not the same between 18s and 18t, with 18t being brighter and crisper while 18s being smoother and more organic. Then, at the other end of the spectrum, you have a different bass tuning. The bass of 18t with M20 module sounds close to 18s with MX module, extended but neutral in quantity. Yes, you have to attenuate 18s bass by more than 10dBs to match it with 18t and M20. Also, I have a feeling that 64 Audio didn't change the mids tuning going from 18t to 18s, but due to sound changes related to bass and treble, the perception of 18t mids is more revealing, more forward, and with a better layering and separation of the sounds, while 18s mids sound more organic.

U18s vs Nio

Finally, a comparison where we have a closer match in bass. Until Nio, I was enjoying the sparkle of tia treble in other 64 Audio iems, but after spending more time with Nio, my ears adjusted to a smoother tonality of its treble tuning. I wouldn't say the treble here sounds identical, and I find 18s to have a little better extension, more refinement, and better controlled crunch while Nio treble is a bit raw and forward in presentation. Bass comparison here is interesting as well. We are talking about DD vs BA, and Nio with M20 is a bass cannon with a noticeable sub-bass lift and very strong mid-bass slam. Dropping Nio from M20 to M15, I still feel the bass quantity is higher than 18s with M20, and for my personal taste I prefer Nio with atom N10 (10dB module). In comparison, 18s bass is less aggressive, more polished, less raw. If you are closeted basshead, 18s might not fully satisfy your craving, like Nio with M20. When it comes to mids, 18s is more refined, better layered, and also a little more laidback.

U18s vs Fourte/Noir

I always had a love/hate relationship with Fourte/Noir. When it was released alongside the U18t, I preferred 18t tuning, but later made peace with it after I switched from silicone to foam eartips. To my ears with silicone eartips the Fourte/Noir treble is piercing, but it becomes smoother and less peaky with foamies, though I still find it bright, even brighter than U18t/12t. Fourte/Noir bass is velvety smooth and textured, not as aggressive in comparison to 18s stronger mid-bass impact (w/M20), but the sub-bass extension is quite similar with its deep analog quality. With mids/vocals in A/B comparison using stock cable, Fourte/Noir vocals sound hollower and more withdrawn in comparison to 18s. I do prefer Noir over Fourte because of its fuller lower mids body which gives vocals more natural tonality, but Fourte/Noir both have 1kHz peak which to my ears makes the sound a bit hollow and nasal, the reason why I prefer 18s/t in this comparison. All just a matter of a personal preference.

Family picture.

U18s vs Oriolus Traillii

To level the field in this comparison, I was using U18s with PWA 1960 4 wire cable. The soundstage depth/height are quite similar, but the width is different with Traillii being wider, creating more holographic effect while U18s being more focused and a little more intimate in soundstage presentation. When it comes to bass, both have a very similar mid-bass punch, perhaps with U18s being a little stronger while Traillii having a deeper and more textured sub-bass rumble. U18s sub-bass extension is no slouch either, but Traillii just has more quantity and more weight in sub-bass. Mids are actually quite similar in this comparison, with fuller body lower mids and natural detailed tonality of upper mids/vocals, though technically Traillii has better layering and separation of sounds in mids. Both have a natural well-defined treble without any harsh peaks, but Traillii has more sparkle and airiness in comparison to smoother treble extension in U18s.

U18s vs VE Erlkonig

There is a slight difference in soundstage expansion and imaging between these two where I find Erl to have a little wider soundstage while both have the same depth/height, but mids positioned a lot closer in Erl while being extended more out of your head in U18s. With M20 module, U18s bass also hits harder, mid-bass quantity is more elevated, while sub-bass extension is similar in quality, just a touch more elevated and textured in Erl relative to U18s. Both have a very similar natural detailed upper mids, but Erl lower mids are fuller and warmer in comparison to U18s being relatively slimmer. U18s lower mids are not lacking any body, but in a relative comparison Erl lower mids are fuller, giving its sound a thicker vocals. With treble, Elk has more sparkle and airiness. Both have a well-controlled natural treble but the upper treble sparkle and air is more noticeable in Erl.


Source pair up.

In each source pair up I was using a stock Premium cable with balanced termination (I have another Premium cable with 2.5mm termination, used with 4.4mm adapter if necessary) to keep everything consistent. U18s is easy to drive considering its 106dB sensitivity which might need only a few extra volume clicks. Also, due to its LID tech, U18s low 8ohm impedance didn’t seem to cause any issues with different output impedance sources, even 10ohm original R6. Also, I didn’t hear any hissing. For your reference, here are my brief pair up notes. And by brief, I just focus on any changes related to signature and general tonality, without going into too many details of technical performance difference.

Lotoo LPGT (baseline) - balanced sound sig, deep enhanced bass impact, natural detailed mids, smooth detailed treble.

Hiby R6 (10ohm output impedance, original model) - a similar signature, with a little stronger bass impact.

iBasso DX160 - a similar signature, just a little more revealing mids.

A&K SP2000 SS - a similar signature with a little bit more sub-bass rumble and some extra treble sparkle.

L&P P6 Pro - a similar signature with more sub-bass rumble, smoother yet still detailed vocals, and similar treble.

iBasso DX300 - a similar signature with a touch more sub-bass rumble, the same natural tonality mids and treble with a little more sparkle and air.

Hiby R8 - a similar signature with an overall slight enhancement of sub-bass rumble, more revealing mids/vocals, and more sparkle in treble.

Galaxy S9 (smartphone) - a similar signature, but leaning a little more toward U-shaped since mids/vocals are slightly recessed, while bass has more impact and treble has a little more sparkle.

Maybe there are some slight variations going from dap to dap, but overall U18s signature remained the same, thanks to LID tech which does work. In comparison, it was a different story with U18t where I heard more variation in sound.



I know, U18s is just one of 3 new 64 Audio releases announced early this year. And I’m well aware of the reaction U18s received on Head-fi when details leaked out ahead of the official release. People wanted something all new and totally different, and I have a feeling it is still to come! From the image of 3 new releases shared during their new product announcement, we already know about U18s, and many are speculating that one in the middle could be a wireless model (just a speculation). There was also a 3rd model will an open back grill, so I’m keeping my fingers crossed for the next big flagship announcement. But it doesn’t mean that U18s release has to be discounted.

A/U18s finally got a well-deserved proper introduction, catering to musicians who prefer mostly CIEMs and audiophiles who go for both CIEM and UEIM versions. Also, I personally think that U18s wears two hats under that “s” suffix. With MX module you can look at it as a studio IEM with more neutral bass and clear focus on mids and treble that should work great for studio mixing and monitoring. But switching to M20 module turns it up to “eleven” with a sound signature for stage musicians and audiophiles who crave natural detailed analog tonality and powerful bass slam without overwhelming ear fatigue. Now, add to that a cool new faceplate design with 64 Audio logo branded apex modules and the package is complete!
This is so weird. I've demoed this and it is different from your impression. Wonder if there is qc issue. Againts U12t, 18s sounds more intense with tighter bass and 12t sounds more delicate and lush with mellower bass.
Thanks for the reviw
Great review and really appreciate all the photos. Thanks!!


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