Jomo Audio Déux


Headphoneus Supremus
Pros: Gooey, syrupy warmth without sacrificing technical performance
- Great body and emotionality, especially with electric guitars
- Impressive spatial performance for the signature and price
- A bass response that's inherently guttural and organic, but customisable as well
- Excellent build quality
- Admirable value-for-money
Cons: Not the clearest, cleanest or most detailed signature
- Warmth may be too much for some
- Not for those who prefer a neutral bass response
- Packaging for ACU modules is rather meek, even though the parts themselves are excellently made
DISCLAIMER: Jomo Audio provided me with the Déux in return for my honest opinion. I am not personally affiliated with the company in any way, nor do I receive any monetary rewards for a positive evaluation. I’d like to thank Jomo Audio for their kindness and support. The review is as follows.

Jomo Audio is a Singaporean in-ear manufacturer run by the venerable Joseph Mou. After achieving massive success with his Signature and Pro Audio line-ups, Joseph announced in mid-2018 three new additions to the latter line as well as a brand new series dubbed Melangé consisting entirely of hybrid IEMs. Within this line-up is the Déux and the Quatré, along with a slew of new technologies including CSU (Cross-Sync Uniphase) and ACU (Airflow Control Unit). Today, I’ll be taking a look at the Déux: A warm, laid-back in-ear with features and performance that surpass its modest price tag.

Deux-10 (3).jpg

Jomo Audio Déux

  • Driver count: One balanced-armature driver and one dynamic driver
  • Impedance: 19Ω @ 1kHz
  • Sensitivity: 105dB @ 1mW
  • Key feature(s) (if any): Two-way CSU crossover, ACU technology
  • Available form factor(s): Custom and universal acrylic IEM
  • Price: S$999 (UIEM); S$1099 (CIEM)
  • Website:
Build and Accessories

The Déux comes in Jomo Audio’s standard packaging: A textured, clam-shell box with the company logo embossed on top. Opening the box reveals an included cleaning tool, an 1/8″ adapter, an airline adapter and the Déux’s laser-engraved, puck-shaped metallic case; all nestled within foam cut-outs for security during transit. An owner’s card with a serial number will also come with all retail units. Inside the metallic case are the in-ears themselves plus information regarding ACU technology. The interior of the case is entirely foam-lined as well, so the in-ears remain safe at all times. As I said in my Haka review, Jomo Audio’s packaging is simple, but it compensates with excellent presentation and style.

Box (5).jpg

With the Melangé monitors, Jomo Audio includes a total of four ACU filters. These come in an extra box resembling a jewellery case. Based on the look and feel, I can clearly tell it’s an inexpensive OEM solution. But, at least it keeps costs down. If the Melangé series were to expand in the future, I’d suggest redesigning the default box to include the ACU filters in a more elegant fashion. Nevertheless, the filters themselves and their storage unit are solidly machined. The latter is heavy and robust with screw holes for the filters to screw into for ultimate security. The 3D-printed screwdriver gets the job done, but I would’ve loved a lighter design and a more secure insert. When swapping filters, the screwdriver would sometimes drift off the filter and onto the shell, and this may cause scratches to eventually form in the long term.

Filters (1).jpg

In terms of design, Joseph once again had free reign. The theme he and his team came up with this time was a mix of clear acrylic resin and silver-gold glitter, along with metallic inlays on the faceplate. It’s a simple design that won’t necessarily turn heads, but it’s well-executed all the same. The varied particle sizes of the glitter make the aesthetic more dynamic and the transparent shell allows a relatively clear view of the in-ear’s innards. Build – as expected – is excellent. There is neither a rough edge nor a bubble in sight and the monitors were finished with an even, illustrious coat of lacquer. Fit is perfect as well; well-isolating yet vanishingly ergonomic. Finally, the monitors come default with Effect Audio’s award-winning Ares II cable, which further adds to the overall value and performance of the Déux.

Cross-Sync Uniphase

Cross-Sync Uniphase is Jomo Audio’s in-house solution to combat phase cancellation. Essentially, standard crossover networks would often cause a driver’s output to become out-of-phase (or mistimed). As a result, sound waves of certain frequencies would collide and cancel each other out, causing unwanted dips in the final frequency response. CSU was designed to prevent this by altering component values and sound tube lengths, along with titanium waveguides. The result – theoretically-speaking – would be higher coherency, more precise imaging and a more stable soundstage.


Photo courtesy of Jomo Audio

Although I can’t A/B compare between a CSU-equipped and a non-CSU-equipped IEM, the Déux does have excellent headroom and linearity for a dual-driver hybrid. Despite its inherent warmth and okay treble extension, it consistently maintains a black background and a rock-solid image. There’s a palpable sense of width and depth that can only come from coherence – rather than any form of artificial recession – and I must attribute that to the works of CSU technology.

Airflow Control Unit

Airflow Control Unit technology is the second of Jomo Audio’s latest innovations. But, this one is specifically limited to the Melangé line of IEMs. What ACU allows the user to do is customise the amount of air present within the dynamic driver’s chamber. Altering this would shift how the dynamic driver behaves and – therefore – how bass is delivered to the ear. What’s unique about this technology is it isn’t a bass switch per se that increases or reduces the output of the driver. Rather, more esoteric aspects like speed, texture and balance are altered to deliver entirely different flavours.


Photo courtesy of Jomo Audio

The filters included with both Melangé products are labelled Impact (Red), Balanced (Black), Energetic (Blue) and Musical(Silver). These are generic terms for nomenclature’s sake, and I’ll further elaborate on their effects in Sound Impressions. Nevertheless, they all screw into the one port located at the top of the IEM which feeds directly into the dynamic driver.


The Déux delivers a warm, laid-back signature hallmarked by a fat mid-bass and a relaxed treble. Unlike most hybrids with this configuration – like the Empire Ears Bravado or the AAW A2H – the Déux shies away from dynamism in favour of a richer, more forgiving presentation; ideal for longer listening or for sensitive ears. Although this may suggest a lack of detail or excitement, the Déux compensates through stage reproduction. Background blackness and image stability both impress despite okay treble extension. So, the weighty, full-bodied instruments have a strong foundation to stand on. Expansion is a hair above average, but it fills headspace with ease – stereo separation: fair, headroom: sufficient.

Deux-5 (C).jpg

The Déux’s instruments carry a warm tinge due to the in-ear’s thick, buttery low-end. Even with the Balanced filter, low-end impact just inches above everything else. Once again, the soundscape remains stable, clean and roomy thanks to CSU, but the elements within it are noticeably harmonic and rich. This isn’t ideal for utmost definition, but it’s vital for the in-ear’s chill, relaxing vibe. Slow electric guitars like the ones on Mark Lettieri’s Slant sound thick, smooth and gorgeously melodic. The warmer tones complement the instrument’s clean amplification, flaunting the sweet harmonies the guitars produce together, rather than emphasising the minutia – like string plucks – or clinical separation for analysis’ sake.


The Déux’s single diaphragm supplies a rich, impactful low-end – pumping air like an analog piston. But, the key word here is analog. The Déux concerns itself less with sheer dynamic impact: Its delivery is slower, warm and lush. So rather than any sort of EDM, it’s most at home with crooner blues like Elvin Bishop’s Fooled Around and Fell in Love or guitar-driven jazz like Mark Lettieri’s Montreal. It won’t necessarily deliver the raw adrenaline a basshead would expect (not with the Balanced filter, at least). But, what it will deliver is a pleasingly sweet tone. Kick drums, cellos and pianos all resonate with the same weighty, harmonic quality, coalesced by a euphonic decay. The charm here truly is warmth and timbre.

Additionally, the bass is admirable technically too. Despite its warmth, sufficient control preserves resolution, layering and speed. With saturated pop tracks like Charlie Puth’s Attention, the kick drum and bass line remain well-segregated from one another. Extension is strong, but there’s a definite bias towards the mid- and upper-bass. This is where the meat and melody come from. The sub-bass is more foundational in nature, but solid nonetheless. Texture and definition are where the Déux falls short. Because of the richer tilt, the bass comes across less rumbly and detailed than – say – Empire Ears’ hybrids. But, this was ultimately by design, resulting in a presentation tubeheads will most likely prefer.


The Déux maintains a well-structured midrange driven by a linear rise spanning 1-4kHz. The lower-mids remain neutral, aiding definition and contrast in place of the upper-treble. But because the region sits in line with the low-end, harmonic content is always present; constantly fed by the richness of the mid-bass. Notes are thick and fat, but never come across congested thanks to the stage’s genuine sense of depth. The background is rock-solid and instruments are physically-sound, so resolution persists. But with that said, clarity and transparency aren’t the Déux’s strongest suits. Micro-details may come across smoothed over, so the soundscape is certainly more musically coalesced than clinically separated.

Deux-13 (4).jpg

The Déux takes advantage of a 6-7kHz peak for articulation – crucial for preventing genres like pop, EDM and rock from sounding overtly saturated. When taken together with its inherent warmth, the Déux straddles the line well between separation and cohesion. The multi-part guitar harmonies in Mark Lettieri’s Slant come together with great musicality. But at the same time, the individual tracks are well-defined too. More transparency would be required for proper mixing work, but it performs impressively at its price range nonetheless. Though, higher-pitched instruments tend to sound more weighty and rich than sweet. Female vocalists and flutes may sound chestier, for example. Whether or not this is a good thing will vary by preference, but it’s worth noting for purists who prefer their instruments sounding a certain way.


Up top is where the Déux will probably be most divisive. Peaks in the lower- and middle-treble add tizz before roll-off. This calmness in the upper-treble reaffirms the Déux’s more laid-back presentation. The resultant response is articulate, but not the most open or airy-sounding. Many will cite a lack of sharpness, contrast and clarity; especially fans of pop, rock or EDM (who happen to be the target demographic for hybrids like these). But, this is ideal for those who prefer longer listening. Melodic genres like slow rock or ambient jazz sing with little compromise to detail. Additionally, the treble takes on a calmer, warmer timbre – imbuing it with organicity whilst maintaining decent transient attack.

Extension is admirable for an in-ear at this price. There isn’t much air past 10kHz, which adversely affects the Deux’s transparency. But, the stability of its image is upheld by CSU technology. Spatial precision along all three axes is strong. Stereo separation is commendable, as well as a genuine sense of height – especially when listening to cymbals and chimes. Despite what should be middling performance here, Jomo Audio’s efforts in time and phase have served them dividends in the Déux. Another aspect of note here is speed. Treble notes touch-and-go very swiftly. This adds sufficient dynamics despite the top-end’s calmness, and rids it of any bright overtones – confirming its warm, feather-y timbre.

Deux-12 (2).jpg

w/ Blue ‘Energetic’ ACU Filter

The blue ACU filter adds palpable energy to the mid-bass; inching close towards the sub-bass. The emphasis lies around 100-200Hz, so aspects like rumble and bloom are altered most. Warmth remains largely unaffected. Instruments and vocals gain a bit weight and authority – lower-pitched ones earn presence too – but they don’t shift much in tone or timbre. Upright basses in jazz music sound lovely with the added gusto, while genres like pop and R&B become more rhythmically exciting. However, busier arrangements in the latter category may end up sounding too saturated or full.

w/ Red ‘Impact’ ACU Filter

The red ACU filter applies a similar boost as the blue filter, but to a greater degree. Perhaps the emphasis is closer to the sub-bass, but it’s too close to tell. Sub-bass rumble now takes centre-stage with the lead melody, delivering the levels that bassheads will most likely prefer. Sub-bass texture and definition are more apparent now as well. The low-end is more guttural, physical and forceful, but there’s a slight trade-off in headroom. Vocals have less space to resonate, but if the music you listen to is predominantly electronic and/or loudly arranged, this shouldn’t be too much of a compromise.

Deux-11 (2).jpg

w/ Silver ‘Musical’ ACU Filter

Despite my musings about nomenclature at the beginning of the review, I must say – Musical is the most apt term to describe the silver ACU filter. Its emphasis lies closer towards the mid- and upper-bass, which boosts the melodiousness of the low-end. The region now has a clearer tone and a more melodic characteristic. The note of the bass is now the star rather than warmth or impact. This is ideal when listening to jazz, but it’s beautiful with pop music too. It adds another dimension to the low-end as a melodic instrument in its own right – rather than just the foundation or the rhythmic drive – which adds to the (you guessed it) musicality of the whole number. It’s quickly become my favourite of the bunch.

w/ No Filter

Filterless, the Déux’s mid-bass is at its calmest. A sub-bass bias results in a drier, rumbly response. Subsequently, its stage is cleanest too. Note definition receives a small boost, but no appreciable gains are made in resolution or transparency. Vocals are now notably emphasised around 2-3kHz, resulting in a chestier, more saturated presentation. So, if you’re looking for increased vocal focus and decreased mid-bass energy, this is the ideal configuration for you.

General Recommendations

The Déux has an agreeable signature that’s more versatile the more you prefer longer listening. But, it does have several tonal and textural hallmarks that make it an excellent piece no matter the scenario. Here are three of them below:

Deux-4 (1).jpg

Smooth, rich warmth with a DD-fuelled bass: The Déux maintains a rich, forgiving profile because of its laid-back top-end. But, its body and heft certainly stem from the bass. The Déux low-end delivers both the impact of a dynamic driver, as well as the euphony from its decay. If your tastes lie in slow rock and ambient genres, the Déux is first-choice worthy.

Considerable imaging and stereo separation in a non-fatiguing response: With slower, warmer in-ears, imaging precision and layering tend to get compromised. However, thanks to Jomo Audio’s considerable efforts in time and phase, the Déux maintains a sufficiently black background and a stable image. So, this means enthusiasts of the aforementioned genres won’t sacrifice too much technical performance to achieve a pleasing tone. You get the most of both worlds.

Customisable low-end response: Through ACU technology, Jomo Audio allows you to determine how you want your low-end delivered. Although the mechanism they have in place isn’t the simplest to use – requiring a tool and very steady hands to operate – it does open up the Déux for proper use with a wide variety of genres. This is ideal if the Déux’s generally warm profile fits your preferences already, but you have tons of genres in your playlist with differing needs.

Deux-7 (2).jpg

But, the Déux’s warmer tilt and calmer top-end may render it less favourable to many as well. If the following three scenarios align well with your preferences, you’d be better off looking elsewhere for your hybrid monitor of choice:

Top-end sparkle, clarity and micro-detail retrieval: The Déux’s treble is reserved in both quantity and extension. Again, it’s a predominantly warm and lush in-ear. Hi-fi enthusiasts will most likely find clarity, sharpness and air all insufficient. If openness and detail-led transparency are what you strive for, Jomo Audio’s Pro-Audio line will better fit your needs.

A vocal-emphasised presentation: The Déux has a thick, saturated vocal range. But, diehards of vocal-oriented music may find it lacking in transparency and detail. Additionally, they may find the low-end a touch too prominent relative to the midrange. If you have a preference for vocals and also long for a DD bass to go with it, the Quatré is a superior choice.

A dry, purely rumble-focused low-end: Unlike most modern hybrid offerings, the Déux’s low-end is warmer and thicker than guttural and rumble-y. There’s a bias towards the mid-bass that favours rock and jazz more than it favours EDM and dance music. If you prefer a more woofer-like low-end, Empire Ears’ and 64Audio’s hybrids will make better options.

Select Comparisons

Advanced AcousticWerkes A3H 2018 (S$399 (UIEM); S$499 (CIEM))

Advanced AcousticWerkes (or AAW) were arguably the first to popularise hybrid in-ears in Singapore. I recently reviewed the 2018 iteration of their 3-driver A3H (1DD + 2BA) and I found it excitingly energetic. Like the Avalon we’ll explore soon, its penchant for dynamic energy contrasts heavily against the Déux’s relaxed presentation. The A3H throws a more vibrant, more exciting image because of its brighter treble. The Déux is fatter and richer, but compensates spatially. The latter is more intimate-sounding with a stage that wraps around the head – more even in proportion and genuine in depth. Conversely, the A3H is akin to a bright, crisp LED screen; detailed and clear, but comparatively less immersive.

DeuxAAW (3).jpg

Down low, both display the rumble and physicality evident of a dynamic driver. But, the A3H is significantly more subtle, as its bass lies further back in the mix. The former then has a cleaner stage and higher clarity. Bassheads though won’t be remiss to call this unused potential. This reservedness also renders its lower-treble sounding more pronounced, while the Déux has better top-to-bottom balance. Resolution is stronger on the latter as a result, as its notes sound more complete; less top-heavy. But, if your cup-of-tea is crisper transients, cleaner soundscapes and sparkly cymbals, the A3H comes out on top. If you like your mids warmer and fatter – and your bass just the same – the Déux takes the cake.

Nocturnal Audio Avalon (S$629)

Nocturnal Audio is yet another Singaporean manufacturer with an eye on the mid-tier market. Their 3-driver Avalon is an in-ear with emphases on treble sparkle and sub-bass physicality. Clearly then, it’s the antithesis of what the Déux has to offer. Immediately, the two clash massively in upper-treble energy. The Avalon comes across sharper, clearer and crisper, but at the cost of balance. The Déux may flaunt less detail, but it’s more pleasing to listen to; throughout long stretches, especially. The Avalon is extremely articulate, but the Déux portrays a fuller and more well-rounded sound.

DeuxAvalon (1).jpg

The Déux has a richer, more present low-end with emphases on the mid- and upper-bass. The Avalon is more sub-bass-oriented, which gives it a leaner, more guttural texture. This results in similar bass clarity and separation between the two. But, the Déux’s dynamic driver gives it superior physicality and thump. The Avalon has a crisper, cleaner and brighter vocal range, where the Déux is warmer and more organic. This lends the former towards audiophiles who heavily prioritise detail, while the smoother, more laid-back Déux finds its audience among more tone-oriented listeners.

Jomo Audio Haka (S$599)

The Haka is one of Joseph’s most balanced and versatile monitors. Although it’s an entry-level piece, it has a knack for sounding pleasing with everything – my only complaints being a lack of treble extension and bite. These sentiments very much carry themselves through against Déux. The Haka is more coherent and balanced, especially around 3-4kHz and 6kHz; where the Déux is most saturated. Here, the Haka has greater headroom, so it comes across more effortless and natural. Conversely, some audiophiles may prefer the Déux’s energy for a more immediate presentation of instruments.

DeuxHaka (1).jpg

Although the Haka delivers a warm, well-rounded bass, it can’t compete with the Déux’s dynamic driver. The latter is superior in texture, extension and impact by significant margins. The Haka gives it a run for its money in overall timbre, but the Déux is the obvious victor down low. Despite the saturation, the Déux also has greater clarity. Instruments are more forwardly-placed and articulate, even if they are a touch forceful. Finally, the Déux has more middle-treble energy, so it’s top-end is crisper and livelier. The Haka may have a blacker background, but the former wins out in air and detail.


The Déux is an immensely appealing piece from Jomo Audio. It’s reminiscent of the Haka in that it strays from Joseph’s clarity-driven house sound in favour of a warmer, smoother, more tonally-inclined signature. And to that end, it uses its dynamic driver in uque ways. Rather than emphasising sheer punch and impact, the diaphragm contributes warmth in a rich, sumptuous manner; reminiscent of yesteryear’s tube-y analog tones. But not to be outdone, modern advances in time and phase preserve resolution, and ACU is always there in case you need a little more (or less) kick. Whether you’re the type to listen for hours on end or die-hards of smooth, lush monitors in general, Déux will definitely do you good.

Deux-14 (1).jpg
you are on fire today