Acoustune HS1650CU

General Information

Redefining Dynamic Driver’s Sound

Adopted special synthetic materials (medical grade) for new diaphragm “Myrinx” which mostly impacts acoustic quality, as well as sound feeling.

Enhancing wider frequency response and/or rich sound field, as well as resolving clouded sound and/or low resolution sound, known as a conventional dynamic driver, through the performance of the new diaphragm, Myrinx.

Performs high sound pressure on all frequency ranges, high resolution, especially on high frequency range, wider sound field optimized by Acoustune Integrated Acoustic Management System, i.e. multi-chamber configuration and wide-range tuning expertise, known as “Myrinx Driver Technology”.



Transducer : Φ10mm Single Dynamic Driver
Impedance : 24Ω
Sound Pressure Level : 110dB/mW
Frequency Range : 10Hz~25KHz
Cable : MMCX Silver-coated Re-cable, L=1.2m (8-core)
Plug : Φ3.5mm plug (gold plated), L-type
Shell : Chamber – 100% Brass CNC milling, Housing – 100% Aluminum CNC milling
Color : Mat Black x Gold
Accessories : Earphone, Cable, Ear-tips (4 types)*, Earphone Case, Cable Clip & Tie, Warranty, Safety Instruction
* Ear-tips: AET02 (F), AET06 (M+), AET07 (S/M/L), AET08 (S/M/L)


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Pros: + Very comfortable and natural sounding
+ Good details without being fatiguing
+ Excellent design and construction quality, together with one, very coherent dynamic driver
+ Good tips included in the package
+ Smooth overall sound with good musicality and euphonics
+ Very versatile sound, works with any music style
Cons: - Picks up hiss fairly easily, especially from sources that would be inclined to hiss, makes pairing a bit harder and more expensive than typically necessary
- Needs a high-end source to sound its best
- Isn't the most sparkly up at the top
- May not be the most technical sound out there, sacrifices some technical proficiency for a more natural and smooth sound
Geometric Brass Design - Acoustune HS1650CU Review

Acoustune HS1650CU is the first IEM I am reviewing from Acoustune, a special Brass chamber, single Dynamic Driver IEM, with a very unique geometric and aesthetic approach. They are priced at 650 USD and my review will be focused on assessing their performance relative to their price.


Acoustune is a large company from Japan, with all their products made and assembled in Japan, so you can expect a truly impressive Japanese quality of them. They have a true quality not only to their final product, but also to their customer service, the accessories their IEMs come with, and to the overall Acoustune experience.

It should be noted that I have absolutely no affiliation with Acoustune, I am not receiving any incentive for this review or to sweeten things out. This review is not sponsored nor has been paid for by Acoustune or anyone else. I'd like to thank Acoustune for providing the sample for this review. The sample was provided along with Acoustune's request for an honest and unbiased review. This review reflects my personal subjective experience with Acoustune HS1650CU. Every opinion expressed is mine and I stand by it, the purpose of this review is to help those interested in Acoustune HS1650CU find their next music companion.

About me


This time I can brag about the package, because Acoustune HS1650CU really comes in a sweet little package! Let's just say it is not only sweet, but they have a better package than most flagships I review, some of them even considerably more expensive.

Starting with the main package, Acoustune HS1650CU comes in a larger cardboard box, inside which there is another cardboard box. Inside that, you can find a fully metallic carrying case.

Acoustune HS1650CU is seated very comfortably inside a foam cutout, and they come with a large number of handy accessories, like a leather / leatherette carrying case, a large selection of tips, and an ultra high-quality, silver plated, Oxygen-Free Copper Single Ended Cable.

The cable has a 3.5mm gold plated jack.

Everything is absolutely outstanding with their package, and HS1650CU reaches my golden standard easily in terms of packaging.

What to look in when purchasing a high-end In-Ear Monitor

Technical Specifications

Build Quality/Aesthetics/Fit/Comfort

Okay, so this is one of the most beautifully built IEMs I've seen in a long while, and also quite similar to IMR R1 Zenith in terms of overall shape, but still Acoustune HS1650CU is a thing of its own.

The IEM is fully made of metal, with a beautiful overall design, and with excellent ergonomics. There is a little part towards the back inner part that may touch the ear and cause discomfort for those with smaller ears. This being said, the comfort is mostly okay for most people.

The cable wraps around the ear, and they are supposed to be worn that way. This means that there are no cable microphonics, and the comfort is pretty excellent. Acoustune HS1650CU isolates fairly well from the outside noise, and they tend to be very good at feeling open. There is no driver flex, and quite honestly, they feel good while being worn.

The cable is actually a very high-quality braided cable that is very tangle-free, made from Silver Plated Oxygen-Free Copper.

Overall, the design of Acoustune HS1650CU is simply beautiful, they have a really unique shape, and from their own words, it looks like the inner chamber has a lot to do with this. The matte black with gold accents truly shines a new light on how to combine elegance with expressivism, strong rich accents with a smooth background, making Acoustune HS1650CU really stand out from the Mass of IEMs I've been reviewing, and giving them a cool edge, and this time not for an edgy look, but for a very stylish and clean aesthetic. The fine work of Japan's best is easy to see, as there is an excellent attention to detail, and every single surface is worked with care, cleaned, and polished, making the entire IEM look even better than a luxury watch.

Happily, on the inside, there are L and R Markings, along with color coding of rings along the MMCX connectors, so you don't have to worry which is the left and which is the right IEM. The cable also has L and R Markings.

The cables do not have ear guides, and are soft when they go around the ears, which helps a lot with the overall comfort. The cable is ended with a 3.5mm Single Ended Jack, and with a larger stress relief.

There is a good selection of tips included in the package, including double flanged tips and foam tips.

Overall, the build quality, aesthetics and comfort are pretty much golden, the IEMs look beautiful, they fit beautifully, and they feel very comfortable while in usage.

Sound Quality

Before I drive in the sonic department, Acoustune HS1650CU is a Single Dynamic Driver IEM, and they have all the inherent advantages of this, including an excellent coherency, and a perfect phase, but furthermore, the driver is made using a very thin and light membrane.

The sound could be described as Full, Dynamic, Punchy, Deep, Impactful, Meaty, Intimate, Wide, Emotional, Detailed, Clear, Clean, Fun, Tactile, and Engaging.

The bass has an excellent extension in the sub-bass, and the quantity of the sub-bass is very satisfying, aiming HS1650CU at a crowd that prefers a warmer and meatier sound rather than a fully neutral sound. The rumble is all there, and there are no distortions, making listening to HS1650CU pretty enjoyable, even at ear-bleeding levels, but also at very quiet levels. The bass decay is on the quicker side, indicating a fast speed for the bass, and they can keep up even with the most aggressive of Technical Death Metals, or complex Electronic like Infected Mushroom, without feeling like they're struggling. The bass texture tends to be a touch more creamy in contrast to its quicker speed, and the mid-bass isn't enhanced quite as much, leading to an agile overall sound, although the impact is very impressive.

The Midrange sounds a touch more lively and open, although the textures have a leaner presentation. The transparency is very good, and HS1650CU feels quite revealing, although the lower mids are lesser in amount compared to the upper midrange, resulting in a more intimacy with female vocals than with male vocals. This being said, HS1650CU doesn't have any kind of issue to present even low baritone male vocals, and they go an absolutely outstanding and beautiful job with guitar solos, even the most aggressive of metals having a juicy and fun presentation. Furthermore, when listening to some sweet female voices, you get goosebumps all over your skin, and shivers, from the way HS1650CU manages to present them so close to you, so natural, and so realistic.

The treble has an excellent extension and air, but it isn't quite as enhanced in the upper treble, as it is in the lower treble. The lower treble bump gives them a good amount of detail, but there's no harshness, the treble having a smoother texture, and there is no sibilance, the bump in the lower treble being moderate enough so it doesn't lead to any kind of harshness. The treble could be said to have enough sparkle to liven up the entire sound, and there are no odd resonances at any point in the sound.

The whole sound is very crisp and well-defined, and well-controlled, HS1650CU being a very authoritative IEM with a punchy, yet really well-controlled sound. They make one of my favorite 700 USD IEMs, in terms of sound alone, and the first time I plugged them in, I felt like "that's good, I just need more of this", at the end of the day, listening to HS1650CU for more than three hours straight, simply listening and not analysing, as those aren't analytical headphones, but very analogue-sounding ones.

The Soundstage size is fairly natural, the width and depth are both equal, creating a good amount of space around the listener. Combined with a pretty darn impressive instrument separation, and a pretty accurate positioning and stereo imaging, HS1650CU is an incredibly enjoyable experience.

Portable Usage

The portable usage is pretty much excellent.

HS1650CU is a pretty light IEM, with a good amount of power, they are easy to drive but also scale with a good source. They isolate pretty darn well from the outside noise, so please pay attention, so you don't find yourself dancing inside a store, because the tune was just that good.

They have a tendency to sound meaty and full, giving the sensation of real music, even while on-the-go, and a slightly enhanced bass and more meatier sound are preferable for outdoors usage, as usually the sound of walking tends to drown out some of the bass in music. The same can be said about the treble, and happily, HS1650CU delivers there as well, the slightly V-shaped signature managing to get through the noise of outdoor usage quite well.

HS1650CU doesn't have a perfect noise isolation, I'd say they have about -15 dB of isolation, which means that you can use them freely while walking without being afraid that you won't hear a true danger, like a dangerous dog barking, or a car's horn.

The leakage is minimal to absent, which means that you could go inside a library and blast some metal without anyone there noticing.

The cables are a touch thick and heavy for walking and running, but they are within comfortable limits, while the microphonic noise is non-existing thanks to the over-the-ear design. If you manage to wear them straight-down, they still are microphonic noise free, because the cable just isn't all that noisy, and with a tangle-free cable, they are surely going to be easy to take in and out while out and about.

Overall, they are very portable and very enjoyable on-the-go, just like HIFIMAN RE800 Silver whcih barely touches the ears while being worn.


Acoustune HS 1650 CU has a lot of enemies in the same price range, but they also make a good call, being made of metal, being designed and crafted in Japan, which is a true heaven, and for having a really amazing and detailed sound for this price range.

Acoustune HS 1650 CU vs Beyerdynamic Xelento - Beyerdynamic Xelento is still a very popular IEM for those who are looking for a really smooth and thick IEM, with a really strong sub-bass and bass, a really thick and smooth midrange, and an extremely smooth treble. The package is similar between the two IEMs, and they both come with similar accessories, but it should be noted that Acoustune HS 1650 CU uses universal tips, while Xelento has its own tip mechanism and you need to rely on the tips included in the package. The comfort is good on both, but Xelento is more of an superficial / Shallow fit IEM, while Acoustune HS 1650 CU has a more typical normal depth fit. Xelento has a bit of driver flex, while Acoustune HS 1650 CU has none. The sound is similar, yet quite different. In raw details, they are similar, but Acoustune HS 1650 CU feels more transparent, and shows more textures and micro-details than Xelento, which instead takes the path for a much smoother and cleaner sound, deeper and creamier, with less emphasis on the treble and the midrange, and with a larger bass. Acoustune HS 1650 CU goes for a more natural and less creamy presentation, for a more natural overall texture presentation. The soundstage is huge on both, but I'd give the size prize to Xelento, although Acoustune HS 1650 CU does have at least as good imaging, if not even better. Overall, if you're looking for a really creamy, thick, bassy, warm and smooth sound, Xelento is more suited, while if you're looking for a really natural IEM, with a warm and thick sound, yet with great details and clarity, Acoustune HS 1650 CU makes a very compelling option.

Acoustune HS 1650 CU vs Campfire Atlas - Atlas is a really interesting IEM because many are in love with it, and for a good reason, Atlas is one of the flagships from Campfire, a really loved company from USA. This being said, Acoustune HS 1650 CU is made in Japan, and doesn't take a step down, having a really amazing package, with at least an interesting carrying case. Atlas comes with a more premium carrying case, and more tips, but this is to be expected, considering that Atlas costs about double the price of Acoustune HS 1650 CU. In comfort, I'd say they are really similar, if anything, Atlas is a little held down because it has driver flex for some users, although if you're really slow and careful with them, I noticed that I didn't get almost any driver flex. On the other hand, Acoustune HS 1650 CU seems to fit pretty much perfectly for all users. The sound is larger, and more grand on Atlas, with more of a peak in the midrange, which may seem a bit unintuitive, since they are always called as being warmer and bassier, but this is because the peak in the upper midrange / lower treble compliments the large bass, to give them both a grand, explosive and yet balanced V-shaped signature. Compared directly, Acoustune HS 1650 CU sounds a bit less grand, but more precise, the impact isn't quite as ferocious as it is on Atlas, but it has more precision, cutting like a Japanese sword. Furthermore, if you're sensitive to upper midrange / lower treble peaks, Acoustune HS 1650 CU doesn't use them, instead being quite even in that area, relying on a more forward overall midrange, and just a more balanced overall tuning, closer to being linear, to sound natural. The two are different, and I'd say complementary, if you're looking for a really large-sounding, grand, impressive, deep and warm IEM, that still holds a fine sparkle in the treble, Atlas still makes a really compelling choice, while if you're looking for something a touch smoother, less large, but more precise, with more agility, and with a more linear signature (in comparison), then Acoustune HS 1650 CU makes a really good offer, especially since it is about half the price of Atlas.

Acoustune HS 1650 CU vs Dita Answer Truth Edition - Dita Truth is actually interesting, because it is pretty much the same price as Acoustune HS 1650 CU, but it has a really really different sound. The package is excellent on both, and both are really comfortable, but Dita Truth has no detachable cables, instead using the Van Den Hul cables they sport to paint a truly amazing image. Furthermore, Dita Truth is focused way more on a really analytical, bright, precise, tight, and sparkly sound, Acoustune HS 1650 CU sounding much thicker, more bassy, slower and less airy. Dita Truth is like a precision surgery knife that shows you details you didn't know existed, but that blade has two edges, because you may not always want that kind of precise painting, and instead would want to sacrifice some speed and detail for a more romantic and natural painting, like the one Acoustune HS 1650 CU paints. If you're looking for a really precise IEM, with a lot of detail, a wide soundstage, and an excellent comfort, being powered by Van Den Hul cables, then Dita Truth is still a favorite of mine, while if you're looking for a more natural, thicker, slower, yet more romantic, experience that makes you forget about the listening, ang switches your focus on music instead, then Acoustune HS 1650 CU makes a really nice offer.

Recommended Pairings

Acoustune HS1650CU tends to pick up some hiss from hissy sources, but they aren't quite as sensitive to hiss as other options, yet this may be noticeable, so hissy sources like Hiby R6 should be avoided.

Acoustune HS 1650 CU + iFi xDSD DAC/AMP - iFi'x xDSD is still one of the DAC/AMPs I can recommend the easiest, especially when you look at the features it has, like the X-Bass and the 3D soundstage, along with Bluetooth and even MQA decoding abilities, making it one of the most ideal solutions if you prefer using your smartphone as a transport, and using an external DAC/AMP for sound. The pairing with Acoustune HS 1650 CU is quite ideal, as xDSD is a fairly neutral, sweet, and wide-sounding DAC/AMP, and if you want to add a touch of further width to your stage, it is right there, at the touch of a button. There is no hiss with this pairing.

Acoustune HS 1650 CU + FiiO X7mkii - FiiO's X7mkii is still very relevant, and one of the most widely used Players among music lovers all around the world, and for a good reason. It has a very vivid and detailed sound, access to wifi, streaming services, and two microSD slots, along with other features that you'd totally enjoy. Paired with Acoustune HS 1650 CU, you get a deep and punchy sound, but X7mkii's quicker speed also makes Acoustune HS 1650 CU a touch quicker, giving them a more precise hit, although they were already quite precise to begin with. The really wide presentation also compliments Acoustune HS 1650 CU well. There is no hiss with this pairing.

Acoustune HS 1650 CU + iBasso DX200 (AMP5) - DX200 and AMP5 are a combo that can not only drive Acoustune HS 1650 CU well, but they can also give them amazing dynamics and punchiness. To add to the mix, DX200 is one of the widest DAPs I heard, and this transfer to Acoustune HS 1650 CU, making them wide and holographic. You also get the latest Android updates, along with streaming services support when going with this combo. There is no hiss with this pairing.

Value and Conclusion

It has been truly fun to review Acoustune HS1650 CU, and I'm sure it will remain in my heart for a long time as one of the most enjoyable IEMs I tested to date.

To be fair, it isn't even a IEM I'd consider to be an experience, more than just an In-Ear, because the first thing I did when I plugged it in, was to listen to music, rather than to analyse how it sounds. The naturalness of the sound and the comfort made me think of music first, and second of what I was using to play it. And I think this is pretty much where all audio-related products should be, enjoyment pieces that make us forget about them as audio products, and think more of music.

The build quality is amazing, but even before getting to the build quality, you're greeted by the finest work of the Japanese Company Acoustune, and their Made In Japan IEMs, HS 1650 CU, in the package, which is not just purely amazing, but also includes things in a new manner, if you're used to IEMs. You get a metallic case, that you could always use to carry your IEMs and a DAP.

You also get Acoustune's amazing cables with their IEMs, and as far as I know, this costs quite a lot when sold separately, and is held in high regards by cable experts.

The comfort is quite excellent, they go naturally around your ears, there's no driver flex and no cable microphonics, Acoustune HS 1650 CU is simply too comfortable to be called a typical IEM. The excellent tips included in the package also help with this.

Overall, the sound is quite natural, meaty, thick, punchy, deep, dynamic and fun to listen to. The upper midrange has a small bump that makes female singers come a touch closer than male vocals, giving them an interesting edge for ACG music, basically Japanese music - which I happen to enjoy quite a lot. This being said, and HS1650CU is very versatile, working well with Classical, Metal and even complex Post-Hardcore music. Electronic music is also one of their strengths, and so is pop, making them a truly good-for-all IEM.

At the end of the day, if you're looking for a warm, thicker, fun, natural, smooth, punchy and dynamic IEM, priced at about 650 USD, with an excellent comfort, with amazing levels of details, and with an overall tuning and comfort that can be only described as "it makes you forget about the IEM, and it makes you focus on the music", then you should totally check out Acoustune HS 1650 CU!

Full Playlist used for this review

While we listened to considerably more songs than those named in this playlist, those are excellent for identifying certain aspects of the sound, like PRaT, Texturization, Detail, Resolution, Dynamics, Impact, and overall tonality. We recommend trying most of the songs from this playlist, especially if you're searching for new most, most of them being rather catchy.

Tidal Playlist

Song List

Bats - Gamma Ray Burst: Second Date
Eskimo Callboy - Frances
Incubus - Summer Romance
Electric Six - Dager! High Voltage
Kishida Cult - High School Of The Dead
Dimmu Borgir - Dimmu Borgir
Breaking Benjamin - I Will Not Bow
Thousand Foot Krutch - The Flame In All Of Us
Gorillaz - Feel Good Inc.
Infected Mushroom - Song Pong
Attack Attack - Kissed A Girl
Doctor P - Bulletproof
Maximum The Hormone - Rock n Roll Chainsaw
Rob Zombie - Werewolf, Baby!
Escape The Fate - Gorgeous Nightmare
SOAD - Chop Suey
Ken Ashcorp - Absolute Territory
Machinae Supremacy - Need For Steve
Ozzy Osbourne - I Don't Wanna Stop
Crow'sclaw - Loudness War
Eminem - Rap God
Stromae - Humain À L'eau
Sonata Arctica - My Selene
ustin Timberlake - Sexy Back
Metallica - Fuel
Veil Of Maya - Unbreakable
Masa Works - Golden Japang
REOL - Luvoratorrrrry
Dope - Addiction
Korn - Word Up!
Papa Roach - ... To be Loved
Fever The Ghost - Source
Fall Out Boy - Immortals
Green Day - Know The Enemy
Mindless Self Indulgence - London Bridge
A static Lullaby - Toxic
Royal Republic - Addictive
Astronautalis - The River, The Woods
We Came As Romans - My Love
Skillet - What I Believe
Man With A Mission - Smells Like Teen Spirit
Yasuda Rei - Mirror
Mojo Juju - Must Be Desire
Falling Up - Falling In Love
Manafest - Retro Love
Rodrigo Y Grabriela - Paris
Zomboy - Lights Out
Muse - Resistance
T.A.T.U & Rammstein - Mosaku
Grey Daze - Anything, Anything
Katy Perry - Who Am I Living For
Maroon 5 - Lucky Strike
Machinae Supremacy - Killer Instinct
Pendulum - Propane Nightmares
Sirenia - Lithium And A Lover
Saving Abel - Addicted
Hollywood Undead - Levitate
The Offspring - Special Delivery
Escape The Fate - Smooth
Samsara Blues Experiment - One With The Universe
Dope - Rebel Yell
Crazy Town - Butterfly
Silverstein - My Heroine

I hope my review is helpful to you!


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Pros: Extravagant presentation and build quality
-Good accessory set
-Stunning quality stock cable with Pentaconn jack
-Extraordinary shell design
-Comfortable fit
-Near-flawless, coherent signature
-Authoritative bass tuning
-Strikingly beautiful mids tuning
-A wide soundstage with fairly good imaging
-Value-for-money pricing
Cons: Poor sound isolation
-Average soundstage dimensions
-Lacks the final bit of technical prowess to be truly flagship-grade
Forget about hybrid horrors, multi-driver maladies, and electrostatic eccentricities, Acoustune brings an unforgettable sound with just one well-tuned dynamic driver.


In the past, great things came in threes, like divas (Mariah, Whitney, and Celine); action heroes (Stallone, Willis, Schwarzenegger); and religion (er, better not). Likewise, for top-of-the-line (TOTL) earphones, there were just Sennheiser IE800, AKG K3003, and Shure SE846. If you aimed for the top you only need to consider those. It was a simple and glorious time.

Come 2018, the prices of flagship in-ear monitors (IEMs) have at least doubled, and there is a mushrooming of boutique brands with spectacular prices, leading to market infatuation, saturation, and fatigue. There’s a yearning to go back to the way things were, of big brands and one marquee flagship to last years, for bragging rights purposes. Something… bona fide.

The search for the bona fide continues too in Japanese brands. You feel a certain assurance (even a glowy, egotistical warmth) when you shop, for example, Sony, Canon, Sharp or Panasonic, emblazoned in modest lettering “Made In Japan”. This is the exact kind of happiness money can buy lol.

So when I mention Nippon DICS Co. Ltd, you might wonder where the heck I’m getting at. Hold your horses. NDICS is a manufacturing conglomerate specializing in medical instruments, lighting apparatus and for us, audio stuff. They designed and developed the Pentaconn 4.4mm, 5-pole jack, and socket. Considering the rapid adoption of 4.4mm as a new standard for balanced audio, yes, they are bona fide alright.

Acoustune is the IEM company under the NDICS umbrella. Relatively new to the game, they first made waves with the HS1501AL and HS1551CU, a well-regarded single dynamic driver (DD) IEMs with a nice warm sound in a distinctive metal shell, at a price that won’t render you in debt. The 1551 has drool-worthy Iron Man colors to rack up some design points too.

Acoustune IEMs deploy a unique Myrinx diaphragm made of medical grade materials that promise less distortion and wider frequency response, compared to conventional dynamic drivers. They have taken things up another notch with the introduction of two new flagships, HS1650CU and HD1670SS, featuring an improved 10mm Myrinx driver and a flashier, 8-core silver-plated copper cable.

Today we examine, in extreme close-up, the HS1650CU. I chose to review this compared to the more expensive 1670SS because I enjoyed the sound and appearance more. They share the same superpowered Myrinx driver, and only differ in housing material (1650 has a brass chamber compared to 1670’s stainless steel) and color scheme (think Black Panther vs. Silver Surfer).

I would like to extend my sincerest thanks to Mr. Takatoshi Seto, assistant manager of NDICS Malaysia for offering a discount in exchange for this review. Acoustune does not have an official store but has an extensive distribution network in Asia. Locally, the HS1650CU retails for MYR2699 (about USD650) and is available through Stars Picker.

This review was originally featured in Headphonesty.

Red hot and eager to please.

Equipment Used

  • Sony NW-WM1A “K” Modded, FW 2.0
  • iBasso DX-200 with AMP8
  • Acoustune HS1650CU
  • FiiO FH5
  • QDC Gemini
Albums Listened
  • Beth Hart & Joe Bonamassa– Black Coffee
  • Daft Punk – Random Access Memories
  • Denean – The Weaving
  • Ed Sheeran – Divide
  • Fleetwood Mac – Rumours
  • Leonard Cohen – You Want it Darker
  • Melissa Menago – Little Crimes
  • Michael Jackson – The Essential
  • Simon and Garfunkel – The Essential
  • The Police – Zenyatta Mondatta

Packaging and Accessories

I’m not Brad Pitt, and will never experience Oscar night when the biggest stars are gifted luxurious goodie bags worth thousands, simply because they’re awesome. The best part is they don’t have to write reviews in exchange lol. If you read gossip rags like me, the goodie bags get as much coverage as the Oscars themselves, and the unboxing must be one squeal of delight after another.

Sometimes though, I get a taste of the good life. Not Brad-Pitt-squealing good, but pretty close. The HS1650CU packaging is so immaculate I wanted to wear gloves before opening them. Of course, I didn’t in the end, because I wouldn’t want some crummy gloves stealing my first touch of these lovelies.

When something is as stylishly-packaged as this, even a cardboard box is worthy of mention. The “Made In Japan” logo might have something to do with it. Inside, a sturdy aluminum case with mirror-finished Acoustune logo houses everything important. The earpieces themselves are displayed like precious gems, while the silvery cable circles around them like a picture frame.

A smaller, faux-leather carry case is also included in case you wanted less grandiosity than the aluminum case. Rounding off the accessory set are 9 pairs of ear tips (AET02 foam tips in M, AET06 double-flanges in S/M+, AET07 silicon tips in S/M/L with focus on clarity and soundstage, and AET08 silicon tips in S/M/L with bass emphasis), cable clip and tie, safety instructions and warranty information.

Real steel. Not mentioned: whether the leather case was made from real cow.

Design and Build Quality

We complain that movies are nothing but remakes and sequels nowadays. In earphone design, there’s barely little ground broken too. The all-too-popular bean shape, bullet shape, and faux custom amoeba shape are repeated ad nauseum. Once in a while, a totally original concept arrives to give the status quo a shakeup, like the movie Inception. This is where Acoustune’s design steps in.

I’ve always thought Acoustune IEMs look overly engineered, but are undeniably cool because of that. Their design language carries over to several models, consisting a smooth outer housing and a rotor-like inner chamber, fastened by three visible screws. The chamber looks like it can spin like a bottle-cap, but it doesn’t, you can stop trying now.

For the HS1650CU, the black and gold color combo unveils layers of luxury and grandeur I never thought possible in the IEM realm. It’s friggin’ jewelry! This is the first IEM where I was enamored with its looks first, and hope the sound quality could somehow be just as good. That’s why I’m sha-sha-shallow. They remind me of the Focal Utopia by Tournaire headphones too, thus explaining the mad lust.

The outer housing is made of CNC-milled 100% aluminum, whereas the inner chamber is CNC-milled 100% brass, a solid one-two punch of pure metal mayhem. I have no doubt this gargantuan build will stand the test of time, how the heck could it not? My only worry is the paint job. Only time will tell if the paint will chip off in the corners like Campfire Andromeda. Contact me again in a year, yeah?


The Rise of the Silver-Plated Copper Surfer.

Acoustune is a new player in the cable game, but have the pedigree to be a solid contender. The stock ARC31 is no laughing matter, an 8-wire cable with original 3.5mm Pentaconn connector, which would probably sell for hundreds if sold separately (and they are!). It is made of 8 badass wires of silver-plated oxygen-free copper (OFC) with triple-shielding and a PVC outer layer for robustness.

Handling the cable is a joy. The cable is soft, supple, bends and submits to will (I mean that in a good way). Coiling and uncoiling don’t leave the cable with any memory effect. Best of all, the connectors, Y-split and Pentaconn jack are impeccably built and are reason enough to justify a separate purchase. My only problem with them is in aesthetics. The silver color does not match with the opulence of the black and gold earpieces, so guess what I did?

I bought another one of their cables with matching colors lol. Because for a truly magnificent performance, all senses should be engaged, and there’s nothing better than eye candy for that remarkable first impression. That’s how I am with earphones. I’m sha-sha-shallow. I can’t comment on smell and taste, however.

The ARC13 is made of 4 cores of artisan OFC, sheathed with durable PVC, braided to pristine perfection, and finished with an elegant 4.4mm Pentaconn connector. Completing the experience is the aluminum case, made just for ARC13 and built to last. I’m reading like a fine dining menu here because the sense of luxury has not escaped from me yet.

Once you go back, you cannot go Black. Wait.

With fewer wires and more sheathing than the ARC31, the ARC13 is more flexible and handles even better. The cable is essentially tangle-free and stays in shape after you coil them for storage. They are almost as malleable and compliant as clay, so you can bet they photograph beautifully.

As for sound quality, the twin twisty twines of terror perform terrifically, providing a balanced sound across the spectrum against a pitch-black background. Note hits are clean, tight and well-defined while maintaining the organicity of 1650’s signature. The only difference between them is the ARC31 bestows a tinge more detail and brightness compared to the full-bodied, able-bodied ARC13.

Fit, Comfort and Isolation

I think I’ve covered all-metal housings before, and the fear of getting my auricles perforated at the slightest misfit or maladjustment. But for the jaw-dropping beauty of the 1650, I was willing to suffer some ear damage if needed. The feeling is akin to wearing a too-tight shirt just for a killer design. I was ready to grin and bear it. With its aluminum outer shell and inner brass chamber, part of me wished for a soft spot in the 1650. Here goes nothing…

And like nothing they went in. The inner part of the aluminum shells, the part that presses against your ears, are impeccably-finished and as smooth as they come. The cable ear guides bear a significant part of the IEM weight as well. So what you have is an inexplicably comfortable IEM despite what the build materials might suggest. TLDR comfy!

Sound isolation is bad. Being a DD, don’t be surprised to find the 1650 amply vented. It lends an air-moving sensation that mimics speakers and relieves some sound pressure from the ear canals, but if you’re commuting or outdoors, the music won’t be entirely your own. Engine noise, wind noise, your mother-in-law, you’ll hear them. Add to the fact that the 1650 has quite a sha-sha-shallow fit, and this is an IEM best used indoors.

I swear, I’m trying my best but can’t seem to get that Bradley Cooper song out of my head.

Deep down, all we want to do is wear masks and spew slander.

Sound Quality

When faced with something new and unfamiliar, I tend to ask about its culinary possibilities. Myrinx? Can it be cooked? It’s metal you say? Never stopped me. The Myrinx driver of the HS1650CU was diligently burnt-in with a slow simmer and low heat, to the tune of 150 hours, just because. I left the 1650 plugged into a source playing easy listening music for a week.

After breaking down the tasty cartilage and releasing its full flavor, I can say that the 1650 sounds more focused and precise. Notes are tighter and imaging rendered more accurate. Nothing breaks ‘em down like slow heat! The main setup used was iBasso DX200 with AMP8 > ARC13 > HS1650CU, a heavenly combination. Also, I used the AET07 ear tips almost exclusively.

Overall Sound Signature

It’s not easy to fall in love. Partly because I’m married (lol), or more likely because I already own a roster of very capable IEMs that transport me to La-La Land at my beck and call. So when I do fall in love, hard, to the extent I visited the Acoustune booth at an audio show several times a day, it’s either something truly extraordinary, or they were giving out free food.

Sting once famously wrote, if you love somebody set them free. No way man. I cling onto them for dear life, like those koala clip-on souvenirs. A new love is intense and irrational, but entices and invigorates, like learning how to use a new organ. Wait. The HS1650CU has what I deem to be… a perfect tuning for my preferences.

Let’s break that down a bit. The 1650 has a neutral-warm signature that plays nice with every genre I fed it. I am amazed by every nuance and facet of its sound from top to bottom. The deliciously rumbly subbass, the cleanly-elevated midbass, gorgeously emotional mids, and the electrifying treble combine to form a coherent, malevolent sonic juggernaut that brings me to my knees.

The 1650 is not perfect by any means. You can easily nitpick some weaknesses, especially in the technical department. For example, notes could be leaner and meaner, the soundstage could be bigger and airier, and overall resolution could be improved. However, the signature, with its valleys and peaks, should be left as is, because the tuning is absolutely spot-on for my tastes, and maybe for you too. It’s neutral-warm done right, and it’s my special sauce.

The entire lineup of The Fragrant Zither, fall/winter collection.


There’s a song about fat-bottomed girls that appreciate the lower end of things. The HS1650CU bass doesn’t have that crassness, but depicts bass on a grand scale, a sweeping, expansive scope. Just… fat. It approaches the epic, but remembers its place in the signature and collaborates for the common cause.

The bass has an unmistakably warm tilt. Notes are full, rounded, and crazily physical! In fact, they carry so much authority they might be your boss’ boss. It pounds and grinds like the hardest worker in the room. Like Rafael Nadal, the tennis player who hits harder than anyone to the point of injuring himself, recovering just in time to win the French Open. He’s so good at this pattern he’s done it 11 times.

So back to the Nadal bass, the polar opposite of a fat-bottomed girl. The extension seems bottomless. There is equal emphasis on subbass and midbass, like twin towers in a frequency graph. Notes plummet with phenomenal impact and air, like angry subwoofers. When it reaches the abyss, you feel it at your throat, and hear it ringing in your ears, leaving you breathless.

But before you declare “Spanish bass monster”, there’s some grace within the madness. The bass punches hard, Superman-hard, but fast, lending a natural decay with moderate speed. Notes flutter away cleanly into the background before bracing for the next impact. The note deftness enables layering to be defined intricately too. It’s not the fastest, nor the most detailed bass, but is deliciously fun with little trade-off in technical ability.


Continuing on the concept of grace, I am often reminded of the REM song “At My Most Beautiful” when describing the mids. Not because of how good Michael Stipe looks, mind you. While the treble and bass are no pushovers nor afterthoughts, the mids rightfully take center stage and leave you in wonderment, with its potent mix of timbral accuracy and clarity. It’s found a way to make me smile.

The mids split the fine hair between warmth and detail right down the center. It’s perfectly balanced. Like the bass, notes start off rich and moist, but end in a palpable texture, like a nutty chocolate cake. The tone and timbre is spot on, and I’ve lost myself in the music many times while the mids enchant and spellbind me. Until deadline day comes and I have to rattle off more words to pass as a review lol.

Instruments sound realistic, with the feeling of a live performance, but 1650 performs like a vocal specialist. Placed in front of the head, male vocals sound raw, emotive, powerful and explosive in turns. It carries the weight from the bass handsomely. Female vocals are equal parts articulate and rich, lush and ethereal, seducing and lulling you into willful submission.

I could go on and on about the mids, and it’ll quickly descend into blubbering. It’s a venus flytrap and I’m the first fly in line. Every string pluck, guitar strum, and worse still, vocal exercise is meticulously engineered to tug into my heartstrings, to awaken my desires, to make me, simply, feel. The 1650 has one of the most accomplished mids I’ve heard, at any price range, and serves as a yardstick for future reviews.

Do the knobs look like bottle caps to you?


I often wonder why people go through all the effort to climb mountains. No trophy, no souvenir shops, no shaman dispensing winning lottery numbers. All you have is the view and a sense of achievement. A thrill-seeking friend obliged an answer, “the journey itself is the reward”. We look back at how stunning the prodigious 1650 tuning has been thus far, and finally, we look skywards.

The airy and articulate upper mids carry into the treble, with tonal accuracy very much intact. Up here, notes are carefree and travel swiftly and playfully. Cymbals crash with bite and outright precision, as do brass and woodwind instruments, straddling the line between energetic and sibilant. At note’s end, the treble decays beautifully, but not before stirring up some excitement on the attack.

The treble is lively and never harsh. Underneath it all, like a pizza base holding all the toppings together, the tunefulness and musicality of the 1650 are absolute. The coherence between bass, mids, and treble is what makes this signature click. Carrying warmth and note weight from the lower registers, the treble is not the most resolute, but in the grand scheme, it fits the signature precisely.

Soundstage and Imaging

Imagine traversing the vastness of the expanding universe, exploring space beyond space, and contemplating the concept of infinity. Mighty huge eh? Now imagine 10% of that size. Not that grand anymore, but still pretty big as long as you don’t compare. This is where we start discussing the HS1650CU soundstage.

For all the heights the 1650 tuning has climbed, it would not sound as it should without the assistance of its soundstage, imaging and spatial abilities. What’s remarkable about the staging is, although the bass is thick, mids are lush and the treble has an organic tilt, the stage proportions provide everyone their own turf, preventing a bloody gang war.

The head-stage resembles a shoebox. Width is arguably the biggest, while height and depth are modest but appreciable. The dimensions allow each component of the music to be spaced out evenly, with a little hint of congestion even in fast tracks. However, the full, dynamic bass presents a rush of warm air to the stage, preventing a totally clean background.

Imaging is focused, accurate, and moreover, realistic. Closing your eyes, you can picture a full orchestra or a five-piece band enveloping you and submerging you into the music. The 1650 won’t wow you with the most atmospheric stage or the needlepoint-precise imaging, but it will floor you with its realism, over and over again.

All dressed up and nowhere to go. Just some guy’s ear canals.


Today we’re doing a special comparison section, pitting together my favorite tunings in different price brackets. All of these wowed me at some point in my life, and if you asked me what my tuning preferences are, rather than describe in detail, I point to one of these babies. For one night only, we have three hammers for a night of expensive hammering.

FiiO FH5

At USD270 the FiiO FH5 isn’t exactly cheap, but is the most budget-conscious of the three. Easily FiiO’s best IEM to date, it could be their statement product if FiiO weren’t constantly improving and releasing new products at a blink-and-you’ll-miss pace.

The FH5 has been described as W-shaped, neutral-warm, or balanced. It’s an all-rounder with slight emphasis in the lower end of things, without diminishing the presence of the mids and treble. Compared to the HS1650CU, FH5 has a more polite, people-friendly bass. Subbass reach is almost an equal to 1650, but hits like a feather, whereas 1650 pushes bass air like an industrial-sized hairdryer.

I can never get enough of FH5’s tiger scratch motif.

Moving up, FH5 has a more rounded and gentle midbass and mids, conveying good amounts of detail but with smoothness more the modus operandi. Notes are wooly as a mammoth and emotive. 1650’s notes have better detail and dynamics, more texture and bite, conveying an utterly realistic sense of well, realism. Even FH5’s glorious vocals have been kept in check by 1650, sounding slightly muffled compared to 1650’s soaring heights.

FH5’s treble is another exercise in smoothness, any smoother and we’ll run out of butter. There is a playful shimmer in some treble notes, but that’s it. 1650 commands more extension, more presence, and a better sparkle, while staying on the safe side of sibilance. For imaging, 1650 is more pinpoint and natural, but FH5 can keep up in slower tracks. For soundstage size, however, FH5 is totally obliterated by 1650, losing out in all dimensions.

Despite FH5 being trounced in every single round, there’s no denying that 1650 might be a direct upgrade for those who love the FH5, everyone except those sensitive to treble. But in this crazy hobby, most people will already find much to love with the FH5, with the nearly three times more expensive 1650 confined to enthusiast circles.

QDC Gemini

We bring out one of the big boys in my collection. At USD1715 with 8 balanced armatures (BAs), Gemini is firmly in TOTL territory, a wallet-drainer and ender of financial stability. When I first heard it I thought I heard God’s voice. It has a divine tuning, balanced, addictive and clear from top to bottom, capable of making believers out of staunch skeptics.

Two highlights of the Gemini, are an unbelievably immersive sound signature, and a bass switch because it’s time to get down and dirty. 1650 starts the battle strong, with thunderous subbass rumble and gutsy midbass leading the way, its earth-moving DD attack and decay sounding more natural, accurate and impactful compared to the Gemini.

Gemini however, has many tricks up its sleeve. He flicks on the bass switch and mounts a comeback, winning in speed, dynamism, detail, texture, and airiness. While nowhere near the visceral grittiness of the 1650, Gemini’s bass is just as listenable.

Pineapple upside-down earphones.

From here, as we climb the ladder from mids to treble, we realize how even 1650’s near-flawless tuning can be tweaked for the better. In general, Gemini injects more liveliness and higher resolution, and is, even more, a vocal masterclass than 1650. It’s like 1650 after months of training, emerging more focused, leaner and quicker, but just as fun.

The Achilles’ heel of Gemini though, is its small soundstage. Immersion has a price, the price of letting the singer and the band come too close to you, and so the sensation of spaciousness suffers. 1650 has better stage dimensions, but predictably, Gemini’s high-resolution means its imaging capabilities are head and shoulders above 1650’s.

Gemini sounds like 1650 unchained, with a similar signature tuned just a bit brighter and tighter, trading some smoothness and body for crispness and utmost clarity. It’s so clear it’ll start giving you directions in life. If 1650 performs in clubs and small bars, Gemini regularly headlines in sold-out arenas, befitting its superstar status. Like Coldplay, but manlier.

Final Words

Acoustune, like down-to-earth philosophers, likes to keep things simple. Take a high-quality dynamic driver, make sure it’s the best you can make, and give it the most musical, uncomplicated tuning possible. No multi-drivers, no messy crossovers, and definitely no histrionic pricing, just solid earphones. They even come with a ready-made upgrade cable to set you on your musical journey.

Some moody grey to go with your warm signature. Maybe some chips too.

Listening to the HS1650CU has been a revelation of sorts. I would never have dreamed of finding such an accomplished tuning at this price range. But the 1650 is much more than that. Like Lex Luger, it’s the total package. From the elegant unboxing, to the premium accessories, to the earpieces themselves, all suggest that the 1650 be priced much higher than they actually are.

But yet, here we are. 2018 and a clear-cut entry for IEM of the year chiefly because it sounds within touching distance of TOTLs costing much more. Acoustune, like IMR’s splendid R1 before this, is spearheading the return of the affordable dynamic driver flagship. It’s a certified, amplified, bona fide achievement. See you at the front of the line.
i will love to read your review of the Gemini
Erfan Elahi
Erfan Elahi
Great review! So joyous and interesting to read your lines. But it will be cool if you could leave your comparison with TOTL flagships like Legend X or Z1r too...


Great review. I've been contemplating pairing this up with my unmodded WM1Z along with the 4.4mm ARC13 cable for a while. Seems like a safe investment to add to the collection.
What is the best in sq the 1650Cu or oriolus mk2 ?
Sorry, missed this bcos it doesn't go in my feed. 1650 has more overall detail and sounds mighty coherent, while MK2 has a more fun and coloured tuning. The MK2's weakness is slight incoherence. You can tell the bass is DD while the rest is BA. If you can live with that it's alright. Overall I prefer 1650 for tuning from bass to treble. MK2 has an airier sig with larger soundstage.