Dunu DK-4001 -hybrid excellence

Introduction and acknowledgment

Dunu are a Chinese brand that as a UK based audiophile I had heard a lot about over the last few years, but not actually managed to hear until pretty recently. Coming across their Falcon-C model (review here) at Canjam London 2018, I was impressed enough with their approach to tuning and design to track down a few other of their hybridmodels to try out. Since then, I managed to spend some time with the DN-2002, but that only served to whet my appetite for their higher end models, so when the chance to grab an open-box DK-4001 from the Advanced MP3 Players website in the UK cropped up, I decided to take the plunge and see what their TOTL model was capable of.

The DK-4001 was purchased privately by myself, with no communication with either the seller or the manufacturer before the purchase or during the review writing process. As always, these impressions are 100% my own, and based on my own experiences with the gear in question. No incentive was sought or received for the writing of these impressions.

Price: c. $899 / £799 (at time of writing)


Dunu DK-4001 rating

Technical Specifications


The DK-4001 is Dunu’s current flagship model, and the packaging reflects its heady status at the top of the product line. The box is similar in size to the fistic packaging used by AKG N5005, being comfortably large enough to fit a small pair of shoes or possibly a game console inside. The IEMs come in a large cardstock type box, with a cardboard sleeve wrapped around it. The usual product specs and marketings pictures adorn the outside, with some pretty detailed info on the design of the 4001.

Slipping the sleeve off, the box underneath is a nice matte black, opening to reveal the IEMs, cable and cable terminators embedded in a layer of black foam. This immediately draws attention to the first unique feature of the Dunu: interchangeable connectors. Like the much vaunted “Awesome Plug” from the Singaporean IEM firm Dita, Dunu have opted to make the source end of their DK-4001 cable interchangeable, allowing the user to swap between “normal” 3.5mm single ended connection and three different types of balanced connector (3.5mm “Pro”, 2.5mm TRRS and 4.4mm Pentaconn). This is all achieved via a lockable 4-pin connector socket at the end of the cable, allowing the user to change between different connectors in seconds.

Underneath the initial layer is a further layer of accessories, including a variety of ear tips (the highlight being some customised Spinfit CP145 in various sizes), a soft leather carry case and 6mm and airplane adapters. This is an unboxing that is unashamedly high end, cramming enough accessories and jazzy presentation inside to make the point that this is definitely a “flagship” product. The finish and optics of the whole thing is very polished, setting an immediate expectation in the mind of the purchaser that these IEMs are AN EXPENSIVE ITEM. While you don’t usually listen to the box (unless you are 18 months old at Christmas time), I think. A well-considered unboxing helps set the tone for what to expect from the audio gear inside, and Dunu have definitely stepped up their game into the big boys league here.

Build quality and ergonomics

As their current flagship, and is an order of magnitude more expensive than anything Dunu have released before. This is reflected in the build, with a premium design evident from the IEM shells all the way down to the lockable connector on the cable.

Starting with the IEMs themselves, they are made from zirconium (sometimes referred to as Liquidmetal), finished in a matt black anodised coating. They look and feel premium in the hand, and the Liquidmetal housing keeps the weight of the DK-4001 in the ear respectably low, despite the all metal build. The shape is reminiscent of its predecessor the DK-3001, but with the less than ergonomic angles of the chassis that hampered that model adjusted so the 4001 sits a lot more comfortably in the ear. It basically resembles a rotund flying saucer with a spout attached, the housings being a little thicker and chubbier than the more slimline profile of the 3001.

The housings are obviously made of two sections fixed together, but the fitting is immaculate, with no gaps or imperfections visible. The faceplate is adorned by a tiny silver embossed Dunu logo, which sits next to a small silver mesh port. The overall effect is undeniably attractive, with the 4001 looking expensive but not too flashy or extravagant.

On the inner face, the edges are nicely angled in, feeling soft and rounded as they hug the bowl of the ear. There is another vent here, a tiny pinhole sitting close to the MMCX connector stem. Those with particularly chunky ears may manage to block the port, but I certainly didn’t notice any difference when pressing the housings in to my ears over and above the usual increase in isolation, so this shouldn’t be a concern.

The nozzle of the 4001 is a nice length, with a lip to allow safe attachment of most type of tips without worrying if you will have to excavate them from the surface of your brain later on if they slip off. The nozzle is covered by a silver mesh wax guard, keeping the delicate innards protected from the usual array of ear gremlins. If you look closely enough, you can almost make out the shape of a dual BA driver sitting directly in the mouth of the nozzle, so the guard is definitely necessary to avoid clogging up the

The MMCX connectors are located on a barrel which looks like it is welded on top of the main IEM body, and sits at a horizontal angle when the IEMs are seated correctly in the ear. I’m not a huge fan of most MMCX implementations, apart from the locking collar on the early Fidue models, and the bulletproof nature of the Campfire Audio connectors. I can now add Dunu to the “Jackpot77 Approved” list of connections (a highly inconsequential and non-revered list, sadly). The ergonomics are a home run here, with Dunu implementing a locking / notched collar which fixes the connectors in place, and applying some sensible angling to the connector housing and pre formed ear guides. The cable is basically guided slightly away from the body at about 15 degrees as it starts its journey, making contact with the inner ear towards the top of the ear and loops back over the ear in a pretty much perfect shape for my large lugs. The preformed ear guides are soft and supple, doing their job without fuss or discomfort, and keeping the IEM nicely locked into place when moving around or walking.

Overall, the 4001 shows plenty of refinement in both build quality and presentation, helping cement the jump into the higher pricing brackets with a mature and well thought out product design.

The cable

The cable included with the DK-4001 is a 4-core twisted design in a fetching burnt copper or bronze sort of colouring, sporting a mix of 7N silver and copper OCC wire inside, and an additional layer of shielding to reduce EMI interference. The wire is sourced from Furutech and finished by Dunu, and certainly fits the bill as befitting of an IEM in this sort of price bracket, retailing on its own for almost half the cost of the total DK-4001 package. The twisted braid (recently adopted by ALO Audio for the current Campfire Audio flagship cables) gives a wire that is thick but eminently flexible, and doesn’t exhibit any notable memory after being stored. Cable noise is also low in everyday use, which is an added bonus.

The real talking point of the cable, as mentioned previously, is the debut of the switchable jack connectors. This marks Dunu as the second notable manufacturer to adopt a swappable “plug”, and to be honest it does surprise me no other manufacturer has jumped on the bandwagon started a few years ago by Dita Audio. With the proliferation of standards and connectors currently out there in the audio marketplace, the ability to use your IEM with all of your different gear by just clipping on a different connector rather than swapping out the whole cable is a definite bonus.

The system Dunu have opted for uses a 4-pin termination at the end of the IEM cabling, into which one of the four (!) supplied connectors can be fitted. The mechanism is spring loaded and looks sturdy and very well machined – no sloppy connection or loose fitting here. The mechanism also “locks” into place once a connector is fitted, ensuring you can’t accidentally separate the cable from the connector while moving around without some serious effort. It feels well thought out and reliable – time will tell on that front, but this sort of innovation is definitely something that more manufacturers need to get behind, in my opinion, so kudos to Dunu for launching their own version.

My only concern with the system is the overall length of the right angled connector once it is attached to your source – the connectors themselves aren’t particularly small, and when bolted on to the barrel of the 4-pin connector on the cable, these do lead to a connector that is a few cm long after the right angle. This means that the rigid bit of the cable basically covers almost the entire width of my Cayin N5iiS when connected – not an issue when you are stationary, but if you intend to use your IEM “on the go”, the extra long connector could possibly act as a lever in the pocket if it came away from the plane of the DAP and got pulled or yanked by something else. This is certainly not a major worry, but knowing how fragile 2.5mm sockets can be, I tend not to use the 4001 with a “smaller” balanced connection DAP in my pocket, just to avoid any potential scenarios that could cause some unexpected grievous bodily harm to my DAP collection. I have to say, in a few months using this and the Dunu Hulk cable, I haven’t actually had any issues, but I am always wary of how I put the DAPs into (or pull out of) my pockets as a result.

Driver design

The DK-4001 marries a 13mm beryllium dynamic driver with two pairs of balanced armature drivers from Knowles. Unlike other five driver hybrids that have hit the market recently, the DK-4001 puts this together in a two-way configuration, with only one crossover point, rather than the more common three or four way setups more familiar in the hybrid market. In another deviation from the norm, the crossover point (the place where the relevant drivers “switch over” and start or stop producing sound) is actually set between the mids and treble, meaning the big dynamic driver is actually responsible for producing the bass AND the midrange, with a dual BA each for the highs and super-highs.

The DD itself is a beryllium PVD design (similar to the recent Campfire Audio models), with the beryllium coating being deposited on both sides of the driver diaphragm for maximum stiffness, rather than the typical single sided application. From reading the excellent interview with Andy Zhao (Dunu chief designer) on the CYMBACAVUM audio site, it appears Dunu were so impressed with the results they actually attempted to patent this dual-sided driver coating, but the patent office consider all beryllium driver implementations to be the same (irrespective of whether they are single or dual sided), so this was not possible. Dunu have also implemented some additional technical wizardry behind the driver, with their ACIS (Air Charging Loop System – no, I don’t know why the acronym doesn’t match the initials either!) providing a spiral bass reflex port design to boost bass frequencies below 100Hz. It is this port that you can see exiting to the mesh covering on the outer face of the driver shell, and Dunu credit it as a major factor in adding the note density and extension that you would expect from a flagship tier product in the lower bass region.

Initial impressions on sound

Given the fact that Dunu have packed a 13mm dynamic driver in the casing and supercharged it with a bass reflex port, you’d imagine that they were going for a “traditional” hybrid tuning, with emphasis on a heavy low end from the dynamic driver and a more traditional BA based midrange and treble. In fact, Dunu are so proud of the output from their dual sided dynamic that what you actually get is a beryllium driver that covers both the bass and mid range, with the four BA drivers just pulling tweeter duty, split evenly between highs and super-highs.

So, how does this translate to what you hear? Well, despite the inclusion of that big ol’ air mover of a DD, the Dunu is actually far from a bass cannon. In fact, while it does have a little bit of a raise in the low end it’s doesn’t actually stray too far north of neutral overall, packing a bass that can best be described as tasteful rather than titanic. There is definitely some thickness and presence to the sound, but the watchword here is control – Dunu have opted to tune the driver with speed and texture in mind, rather than outright bass quantity.

The overall sound is fairly linear, with somewhere between a gentle U and a flattish W curve to the overall sound, with the 4001 extending emphasis on both ends of the spectrum. There is also a notable push in the lower mids, which adds a little prominence to the vocal ranges in the stage position. This is balanced by another slight raise (to my ears, anyway) in the lower treble area, adding a little zestiness in the upper frequencies, This isn’t a ruler-flat attempt at neutral, but it still sticks pretty close to an overall neutral sort of tonality – this is certainly not one of the fabled Dunu treble cannons from years past, retaining smoothness and control throughout the ranges.

Note weight isn’t particularly heavy, with the midrange and treble having a reasonable sense of body without any stuffiness or thickness. The 4001 doesn’t have the sweetness in the vocals that the DN-2002 hybrid had (my only other long-term listen of the Dunu hybrid series), but it does swap that syrupy tone for a more “real” sound to the whole presentation. Timbre of instruments like piano and violin, and both male and female vocals feels spot on – singers sound like they are supposed to if you were hearing them live, not a stylised interpretation of their best (or worst) aspects. This is another side-effect of Dunu’s flagship tuning aspirations, with the emphasis firmly on presenting a clear and accurate sonic image.

One thing that will help the 4001 when comparing to other high-end IEMs is the natural resolution on display. Make no mistake, this is a seriously resolving IEM for the price, and while it might not quite scale the heights of flagship models from Jomo or the Zeus from Empire Ears, there is an absolute sackful of quietly-resolved detailing throughout the whole frequency range. Bass detailing and texture is top notch, and little sonic snippets like formative breath sounds or background room noises are presented cleanly and without masking. It doesn’t necessarily scream detail on first listen, but once you have spent some time with this IEM, you will be hard pushed to find anything particularly lacking in that respect, no matter what you compare it to.


There is a slight emphasis under 80Hz (helped by the ASIC bass-reflex port) which gives a solid grounding to things, but the 4001 is adequate rather than excessive in the real sub bass regions, giving a clean physical presence down low but nothing like the ear shaking thrum of the CA Atlas. The bass stays relatively flat from the deep sub bass to lower mid-bass, tapering down slightly as it exits the upper end of the bass ranges to provide a clear transition to the mids. As both ranges are produced by the same driver, there are none of the usual hybrid coherency issues here, with the 4001 transitioning smoothly and without any bleed or masking.

Moving the “thumb” further down the frequency range from its traditional home in the midbass adds solidity to the sound without overly warming the stage above. Bass guitar and drums sound taut and muscular, with a good sense of physical impact. Again, the 4001 draws the line just short of real viscerality, but there is a “realness” to the weight of each note which gives the rest of the presentation a solid foundation to work off.

Starting with my usual sub bass testers, “Heaven” by Emile Sande provides a healthy but not overly subby bass underpin to kick off the track. Extension is good, and the quantity is somewhere between neutral and full. This should be enough to keep most listeners happy with the volume, and keeps the track from feeling thin or sharp in the ranges above. Loading up “Why So Serious?” from The Dark Knight OST, the subterranean rumble that kicks in around the 3:26 mark is again present, if not excessive. It feels low and gutteral, with a roundness to the bottom of the notes as the vibrations go off in your ear like a distorted heartbeat.

Switching to mid bass, “Bad Rain” by Slash helps emphasise what this driver is really about. The kick drums and snares hit with a real punch, conveying a sense of the drum head flexing in the ear with each strike. The growling bass guitar pick that kicks in around 20 seconds or so into the tune is nicely weighted and full of menace, the texture of the strings vibrating as they are plucked coming through loud and clear. It isn’t overly heavy in terms of quantity, sitting a little below my ideal preference, but above the neutrality waterline.

Another mid bass tester I enjoy is “Hello, It’s Me” by Sister Hazel. The slinky bass guitar that opens the track is loose and limber, again resonating with bags of texture as it opens up into the track proper. On bassier IEMs the mid bass in the mix can fill the whole bottom half of the soundscape with liquid chocolate. The 4001 presentation is a little leaner and chalkier than that, the big beryllium DD showing a light touch and excellent speed. If it weren’t for the physical oomph that occasionally rears its head, you could almost imagine this being a BA driven bass, the control and decay is that taut.

“Get Lucky” by Daft Punk loosens the low end up somewhat, the 4001 dropping low as the bassline keeps descending. It keeps the definition between each note, giving a textured and well extended rendition, not losing emphasis at the outer edges of the ultra smooth bassline as it gets lower. The feel is a lot more liquid here, with a toetapping sense of rhythmic drive.

People seeing the size of the DD being used and assuming this IEM will be a bass cannon will be a little underwhelmed, but for most listeners, the tuning in the low end sounds just weighty enough to be satisfying, and just technical and quick enough to match the rest of the tuning higher up. This is a connoisseur’s take on audiophile bass, and a pretty decent take at that.


Normally in a hybrid IEM this is the section where you usually talk about coherence as the two differing driver technologies trade duties. With the 4001 there is no need to discuss that, as the dynamic driver takes care of everything up into the treble. What you get instead is a transition that is smooth as butter, with no overhang of warmth or overlapping tones from below. The midrange is pretty neutral in terms of weight, neither full nor overly thin, with sharpened edges around notes but nothing too excessive. There is a push to my ears around the upper midrange, pulling vocals a little further forward on the stage than a strictly neutral position, and giving a little edge to some higher-pitched vocalists. It isn’t over cooked or offensively hot, but if you are sensitive to frequencies in the high-mids, you probably want to check these out before buying blind just to make sure.

Starting with vocals, the Dunu has a clean and fairly “true to life” tuning, not artificially sweetening or smoothing over male or female voices. There is no lack of musicality, but if your favourite singer sounds like a sack of gravel being beaten to death with an elephant, don’t expect the Dunu to make it sound like Ol’ Blue Eyes or Elvis Presley. Firing up “Hold Back The River” by James Bay, the DK-4001 captures the breathy and emotional delivery of Mr Bay well, pushing the singer forward towards the listener. It also captures the ghost vocal from the backing singer that slowly drifts into the audio around the 50 second mark very cleanly, resolving the faintly audible voice underneath very cleanly and allowing the listener to clearly discern it over Bay’s louder delivery.

“Song For Adam” by Gregg Allman is another song that practically drips with emotion, being Allman’s last recorded track before he sadly passed away of throat cancer. The Dunu flagship again does a good job capturing the rawness and emotion present in the track, shining a torch in the fine cracks and gravelly breaks in Allman’s once liquid-smooth delivery, and the almost phlegmatic delivery. The midrange push comes to the fore here, allowing the listener to hear the formative sounds as the mouth shapes the words around the wetness of the singer’s throat.

“The Valley Runs Low” from Joe Bonamassa’s acoustic Carnegie Hall concert sounds vibrant, the chiming acoustic guitar and various orchestral instruments and drums all playing through with a refreshing lightness, giving the song a sense of rhythmic drive without sounding too thick or heavy. This song can sound addictively sweet or rich on some of my IEMs, but the Dunu go another way with the presentation here, adding an almost souffle-like lightness of touch to the violin and guitar that allow the song to float past the listener in a very enjoyable fashion. The gospel chorus on this track sounds harmonious, voices blending together but still retaining enough distance between them in the stage to be easy to separate and follow individually in the listener’s ear. “Give Me Some Light” by Canadian blues man Matt Andersen is another track that benefits from this sense of air, the mid-tempo soul/blues of the track benefitting from the healthy sub-bass of the DD and the lightness of touch of the upper registers – this is one of my favourite tracks of recent times, and the Dunu has had me tapping my toes and losing myself in this on more than one occasion.

The Dunu sound particularly clear with acoustic music, bringing things like voices and acoustic guitar to the forefront of the sound. “Shallow” from the A Star Is Born soundtrack sounds almost too forward, the 4001 pushing Lady Gaga’s vocal right up front and stopping just shy of making them feel shouty. Bradley Cooper’s lines sound a little more laid back in comparison, sitting just a little behind and slightly more in line with the bass and drums. Regarding harshness, the Dunu does a good job steering clear of unpleasantness once you have found the right tips for your own ear anatomy, but it definitely sails close to the wind, so may be a little much for some.

Cranking up some more aggressive fare, a few favourite Slash tracks are up next on the playlist. “World On Fire” and “Shadow Life” are both lively, the guitar riffs firing out with a splash of vinegary sharpness. The bass underpinning gives the guitar chords a little weight, but this is more of a sharp and fizzing sort of sound rather than a fat wall of noise. This isn’t a monitor that will absolute floor you with the weight of sound, preferring to hit you with speed and a serrated sharpness to the edge of notes that gives the midrange some bite. The quick fire riffing sounds muscular and nimble, jumping around with short, staccato bursts in around Myles Kennedy’s falsetto vocal and the tight-as-a-drum rhythm section to give the songs a propulsive sense of drive. The phrase PRaT (Pace, Rhythm and Timing) gets over-used somewhat in audiophile reviews, but the DK-4001 is definitely a monitor that feels tight and coordinated, giving a good sense of animus to faster paced tracks.

Sticking with Slash tracks, “Starlight” is up next to start my sibilance testers. With the Spiral Dots attached, the Dk-4001 passes this test easily, Kennedy’s ultra-high wailing definitely feeling emphasised but still smooth and strong in the ear. Ditto for the dissonant harmonics in the intro, with the guitar definitely making an impression but not unpleasantly grating in the process. The clarity of the DK-4001 is again evident here, with the subtle vibrato of fingers on guitar strings and the subtlest of background studio noises coming through cleanly around the 0:33 mark – these are easily masked on less resolving monitors by the body and reverb of the guitar notes.

My other go to for sibilance or vocal harshness is “Whiskey And You” by Chris Stapleton, and again the 4001 passes the test without any major issues. There is a velvety richness to Stapleton’s voice that is brought out by the Dunu with its midrange push, giving the song a warm tilt without losing the trademark grittiness at the 1:46 mark, which can sound a little like nails on a chalkboard with hotter monitors. The Dunu remains controlled here, presenting the rough edges of the delivery in their warts n’ all glory, but not making them unpleasant to the ear.

Overall, the midrange is well-judged and carefully tuned to complement the overall sound of this IEM, giving it an enjoyably crunchy but not-too-light tone and some serious detailing. It IS sculpted, so won’t be the flattest tuning you will ever hear, but the emphasis is tastefully done and not over cooked. It won’t be the final choice for fans of thick or super-warm mid-tones, but if you are looking for something with a realistic timbre and a little air in between the notes, the 4001 could sit very close to ideal for you.


The treble on the DK-4001 is catered for by the four BA drivers sitting alongside the over-size dynamic driver, with two armatures dedicated to the highs and two to the super-highs. It bears most of the hallmarks of a classic Knowles armature high end, with plenty of extension (out to a Hi-Res 40kHz) and a strong emphasis on detail and clarity. Given the stated extension, the treble on the DK-4001 is actually pretty well controlled, staying strong up into the high registers but not carrying any unnatural peaks or emphasis. It is treble that is clean and crisp, with a delicate edge to notes and a sharpness that is refreshing rather than abrasive. There is plenty of body to instruments like the violin, with “Chi Mai” by Duel presenting the high violin and swirling keyboards with a restrained but solid sense of physicality, the notes hanging in the air and filling the top end of the soundstage. The treble feels quite clean and weighty, sitting somewhere between dry and smooth in terms of texture.

Cymbals are roughly neutral in terms of emphasis, with a crisp “tsssk” sound driving the hi-hat led percussion on “Go” by The Chemical Brothers but not overshadowing the propulsive bassline or swirling synthesiser that make up the rest of the track. There is plenty of detailing on the cymbal strikes, each crash shimmering slightly then drying up pretty quickly. It carries just enough decay to sound natural, rather than splashy or emphasised, which sits well with the rest of the sound.

The DK-4001 possesses an excellent sense of articulation, with notes and phrasings on the violin strings in the previously mentioned tracks being clearly audible as the notes shimmer and decay. There is a moderate sense of “sparkle” to the presentation, with a slight hint of sweetness and a delicate final flourish on the edges of the notes as they decay. Classical instruments like harpsichord really shine on the Dunu, staying strong enough to make their presence felt in my classical tracks but still having a lightness of touch that avoids becoming overpowering. I don’t listen to much traditional classical music, but I am a big fan of classical fusion like the aforementioned Duel, The Piano Guys or Escala, and the DK-4001 is very well suited to these genres.

Detail levels are in the high to very high bracket here, the quad-BA setup presenting every last scrap of treble plankton to the listener on more complex tracks without any huge sense of strain or effort. Scuffed strings and harmonics at the edge of guitar notes come through cleanly, and small room sounds and directional cues are also fairly easy to pick up. In terms of rooms, the treble doesn’t sound like it is presented in a closed venue, giving the upper end of the music a nicely open feel. It gives the impression to me of notes playing out into an open field rather than hitting the wall of some imaginary soundscape and reflecting back.

“Oceanic” by Bond is another classical/fusion track I like using for treble, with an atmospheric synth-heavy background and multiple layers of violin and other high-pitched instrumentation. The DK-4001 handles this smoothly, sweeping sounds around the top of the soundstage with a delicate shimmer to the metallic percussion and chimes. There is a power and heft to the higher end.

Overall, the treble is one of the big areas of strength for the DK-4001 for my tastes. It presents a highly detailed sonic image, with a sense of solidity and weight that avoid overly sharpening notes but still give plenty of resolution and a dose of much needed air to proceedings. It feels coherent and balanced, and a good example of how to tune a top end that isn’t necessarily bright, but still packs in plenty of upper end volume and quality without overwhelming anything underneath.

Soundstage, separation and layering

The DK-4001 presents a decent lateral stage size, showing good width across the X-axis. Despite this, the stage isn’t massively huge or diffuse, with a comparatively shallow sense of depth. The Dunu places most of the instruments in a fairly thin oval, keeping individual strands discrete and clearly separated but without a large amount of black space between each one. As a result, imaging is roughly average for an IEM in this sort of price bracket, doing nothing particularly wrong but not grabbing the attention either. The lack of depth isn’t a killer flaw, but does become more noticeable when comparing the 4001 against other TOTL contenders.

As mentioned, the separation is very good, with the Dunu doing a sterling job of keeping everything in its own little slice of the sonic universe in even the most congested tracks. Throw something like “Coming Home” by Sons Of Apollo at it and the five drivers barely blink, layering sound upon sound as close as an award winning onion, but keeping each layer easily distinguishable. Again, this is where the clarity of the Dunu flagship comes to the fore, the natural resolution of the tuning and leaner note weight keeping everything taut and clear in the overall presentation.

Tip Choice

The DK-4001 is a fairly ergonomic design, so will accommodate most after-market tips. For my particular ear geometry (I have very large and cavernous ears) I only got an average seal from the included tips. Given the price bracket this IEM operates in, that shouldn’t be a problem for most purchasers, as I imagine most users are likely to have a raft of tips in their collection to try.

I settled on the Final Audio E-type tips and my trusty Spiral Dots (size L) as my preferred tip choices for the larger-eared gentleman. On balance, the Spiral Dots just edge it for me on comfort, and provide just a hint more balance in the upper reaches of the sound along with a comfortable and robust seal to maximise the depth of the bass. I have worn the DK-4001 for 4 hours straight with the Spiral Dots with no discomfort and only minimal need to readjust as I moved around, so if you do have a pair, I strongly suggest you try them to see if they work as well for you.

Power requirements and synergy

The 4001 isn’t a hugely thirsty monitor to run, requiring a fairly average level of power to generate some decent decibel levels in the ear. However, I suspect the large beryllium driver packed inside needs a little power to reach its optimal performance, so my preference is to run these on high gain from my gear to get the best out of the low end.

Giving a little more juice tightens up the bass response a little to my ears, and provides just a hint more body to the notes, filling out the response slightly (it is more marginal than massive, but does seem to be noticeable to my ears even after volume matching).

In terms of synergy, the provided cable means that the 4001 can be used with more or less any source currently on the market. From personal experience, I would suggest using something that errs more to the warm or organic side to make the best of the provided driver tech inside. Something like the Cayin N5IIs running balanced gives the bass a nice sense of heft, and despite its neutral tone in the upper end, manages to present the slight peak in the high mids with a smoother and more natural edge than some of my “lesser” sources like the Shanling M0.

I actually prefer this pairing over the Ibasso Dx200/amp8, which was usually one of my “go to” setups for my higher end in-ears. While the Amp8 driven Ibasso gives a beautifully natural tone to the presentation, the 4001’s average imaging doesn’t really take full advantage of the Ibasso’s stellar positional prowess, not giving any significant advantage to my ears over the Cayin matchup. This is an IEM that can scale in detail very well with more resolving sources, but not hugely in other aspects of the presentation (at least to my experience), presenting a similar sort of sound from most of the gear in my collection.

The Fiio M11 provides a good solidity to the bass presentation, the ample power on tap from Fiio’s latest all-rounder allowing the big dynamic driver to lay down some pretty solid feeling beats when required. The slightly more digital / analytical presentation of the M11 in the upper registers actually still plays well with the DK-4001, allowing the quad-BA drivers up top to bring out plenty of fine detail without over-sharpening or brightening the sound. Given the general tone of the M11, I wasn’t expecting miracles, but this is actually a very good matchup. One caveat – the SE and balanced outs on the M11 are slightly different in overall presentation, so it is definitely worth running the Dunu in either 2.5mm or 4.4mm configuration with this particular DAP to get the most out of the matchup.

With my current “high-end” rig (Cayin N6ii with A01 module), the 4001 take on the best qualities of the N5IIS pairing and kick it up another notch. As with the Ibasso, I don’t feel there is a huge amount of scaling going on with the imaging, but the general solidity of the sound takes a step up, and the 4001 ounces more organic, but without shedding any of the fine detail. As mentioned, certain aspects of this IEM seem to scale with better quality sources, but it doesn’t need a real high-end source to achieve a great sound.

One other surprisingly enjoyable matchup is my burn-in/road trip rig, the Sony NW-A45. It doesn’t quite maximise the resolution of the 4001 like the Cayin or the Ibasso, but the wide presentation of the sound and the classic Sony bass warmth give a nice tilt of musicality to the 4001 for occasional listening, if you just want to pick up and play.


Stealth Sonics C9 (c. $1499) – 1xDD 8xBA hybrid CIEM

This may seem like an unusual comparison, but the C9 is the CIEM sibling of the universal U9 model from Singapore manufacturer Stealth Sonics, and shares a more or less identical signature apart from a slightly raised bass, so felt like a better comparison than the universal model. The overall sound is close enough to the DK-4001 on enough levels to make this an interesting A/B for me.

Starting with the bass, the C9 has slightly more midbass presence, but only marginally. Neither are full on basshead IEMs, but the C9 just has a little more oomph down low compared to the Dunu. This gives the C9 a slightly warmer overall tonality in comparison to the colder and more clinical DK-4001.

In the midrange, the DK-4001 has a more emphasised vocal range compared to the more neutrally positioned C9, with the upper-mid peak of the Dunu helping pushing vocals slightly more to the forefront. The C9 counters with a richer and meatier presentation of both male and female vocals, but again isn’t a million miles away from the Dunu. Guitars and stringed instruments are presented excellently on both, with both carrying enough edge and crunch to really kick tracks like “World On Fire” by Slash into a higher gear. The Dunu presents notes with a slightly sharper edge, but like the vocals also with a lighter and less dense body. The C9 again feels fatter and denser, but without losing anything in terms of resolution or crispness. The best analogy I can think of here is between a rapier (the Dunu) and a katana (Stealth Sonics). Both sharp enough to cut through the chunkiest of tracks with ease, but one just carrying a little more weight behind it than the other.

With regards to staging, sound feels deeper on the C9, with a better sense of position across the z-axis to give a more spherical stage. In comparison, the 4001 feels a little wider and flatter, presenting as a more oval stage. Spatial cues are much more apparent on the Stealth Sonics model, giving the music a more three-dimensional mental image, painting instruments with a more precise location on the stage. This also has the effect of making the separation and layering a little easier to pick out on the C9, due to the increased sense of depth. The 4001 is still a capable IEM in this area, but the C9 is definitely a class above here for me.

In terms of overall shape of the tuning, the C9 has a smoother and flatter frequency response across the spectrum, with instruments sounding a shade fuller and more natural, and no obvious spikes or areas of emphasis. Detail is more audibly emphasised in the midrange on the 4001, but the C9 actually resolves as much (if not more) as the Dunu. Taking one of my favourite testers (“Palladio” by Escala), the subtle click in the intro bars as a musical stand is adjusted in the background is heard as clear as day on 4001. The C9 still captures this piece of sonic background info, but it isn’t pushed as far forward into the consciousness of the listener, settling a little further into the audio background. Regarding tonality, sounds feels sharper and colder on the 4001, with a more clinical tone – the C9 is warmer and more organic sounding in direct comparison.

Driving requirements are roughly equivalent across both IEMs, with both responding to more voltage with a similar result on the bass. Neither are particularly hard to drive.

Accessories and packaging is good with the C9, with two cables provided as standard and a decent unboxing and accessory loadout. The Dunu takes the lead in this aspect, however, with a more ostentatious unboxing and an excellent array of accessories (including a very nice leather case). The real differentiator between the two is the new Dunu cable, however – it sports their new interchangeable plug design at the end, and comes as standard with 2.5mm/3.5mm/3.5mm balanced/4.4mm connectors in the package. This is a killer add-on for something in the Dunu’s price bracket, and pushes the Chinese flagship ahead of the Stealth Sonics model here.

Overall, both IEMs play in the higher end of the scale when it comes to both resolution and overall sound quality, with a similar but not identical approach. The C9 has a slight technical edge with better imaging and staging, with similar levels of detail to the Dunu hybrid. It also manages to eke a little more bass out of the smaller DD driver without sacrificing any control – this, allied to the slightly more organic and natural feel to the sound mean that if I had to choose one IEM, I would probably lean towards the C9 for my particular preferences. That said, the Dunu keeps pace on multiple fronts admirably, which is pretty impressive for an IEM that is less than 2/3 of the price. If you are looking for an IEM with a thinner but more emphasised midrange tonality and prefer your sound on the colder or more neutral side of the street, the Dunu would be my suggestion – if you are a fan of warmer or more organic tunings (without losing any detail) or a holographic stage is more important to you, the C9 is an easy recommendation here.

Campfire Audio Solaris (c. $1499) – 1xDD 3xBA hybrid universal

The Solaris is the current TOTL monitor from Campfire Audio, sporting a hybrid design with their 10mm ADLC dynamic driver, a ported BA and a set of twin BAs covering the high end, pushed through their TAEC tubeless chamber technology to produce the final output. It is generally acknowledged as a heavy hitter in the current TOTL landscape, so while it is technically in the next price bracket from the Dk-4001, it again shares certain commonalities in tuning and overall approach that make this a useful comparison (for me, anyway).

With regards to the bass, both IEMs have a similar approach, using very capable dynamic drivers to provide a sense of physicality. Both IEMs also favour speed and definition over absolute quantity, with the DD decay tuned to keep pace with the quicker BA drivers in the upper ranges. The Solaris bass feels a little deeper, with a sub-bass weight that gives the sound from the CA flagship an almost speaker-like feel of substance in comparison to the less warm and weighty Dunu presentation. Both drivers are quick for DDs, with the Solaris possibly having the snappier of the two responses, but not by much. Texture and detail are uniformly high, with the Solaris again just shading it in the finer nuances, but we are definitely talking very small margins here. Both IEMs take EQ well, and both can slam when required, giving tracks a sense of physical presence that all-BA setups just can’t quite match. If you

Vocals are a little sharper and crisper in presentation on the DK-4001, feeling a little thinner and more etched in comparison. The Solaris midrange has a slightly thicker and more analogue tonality with a shade more warmth, with less obvious crispness. Detail level is again fairly evenly matched, with both IEMs dragging out layers of fine detail where required. The Dunu is probably the more obviously resolving IEM of the two, with a cleaner and less full midrange allowing slightly more air in the stage and bringing small scuffs and room noises further forward into the listener’s consciousness. The Solaris is not lacking in resolution, but on tracks like “Palladio” by Escala, the small room noises and clicks around the 20 second mark are more easily apparent on the Dunu, with the Solaris presenting them further back into the overall soundscape. There is a slight dip in the midrange I hear with the Solaris which helps separate the vocals from other instrumentation, whereas the Dunu is more “pushed” in the same region, giving an interesting differentiator (and accounting for the more obvious detailing in certain frequency ranges).

Guitars and other rock instrumentation sounds richer and thicker on the Solaris, taking a fuller tone in comparison to the sharper and crisper feeling DK-4001. Neither is better or worse here, so it will depend on your overall preference for sound – if you like your music colder and crispier, the Dunu takes away some of the organic warmth and weight of the Solaris and sharpens up the edges of the notes somewhat. If you want a fuller, meatier sound with more of a vinyl/tubelike presentation of instruments, the Solaris would be a better option here. One area where the Solaris does pip the Dunu is in timbre – the Solaris gives that “real world” sense of presentation to some instruments like you were hearing them in a live music venue. The Dunu has more of a “studio” feel, again presenting instruments in a lifelike manner, but lacking that live warmth that you would get on stage.

Highs are detailed and extended on both. The Solaris has the smoother of the two presentations here, but no lack of sparkle or detail. Again the Dunu is the thinner and more “etched” of the two in comparison. As with midrange, this will come down to preference more than technical prowess, with fans of a sharper and hotter style of treble leaning towards the Dunu, and people liking a treble with decent weight but still a healthy dose of sparkle and liveliness probably leaning more towards the Solaris.

In terms of coherency, both models buck the usual “hybrid” stereotype, presenting well integrated and very coherent sonic landscapes, making it very difficult to identify where the overlap between the drivers occurs. If I had to call, the crossover to the more BA driven sound on the Dunu is slightly more obvious, but both have managed to integrate all the drivers into a nicely blended package. Soundstage size goes to the Solaris, which presents a stage that is a fair bit deeper and more spherical than the Dunu, without losing anything in width to the Chinese flagship. Separation is a little more emphasised on the Dunu, but layering and imaging is a clear notch up on the Solaris to my ears, with the campfire model locking instruments down precisely in a three-dimensional space inside (and slightly outside) of the head. Note size is also bigger on the Solaris, with the whole presentation being moved slightly more forward towards the listener in comparison to the more neutrally positioned Dunu.

In terms of build and fit, the Solaris are a MUCH bigger IEM than the DK-4001, with shells that rival the old school JH Audio range for sheer size. They are still comfy to wear, but are notably more difficult to get a perfect fit so require more tip rolling, and feel more “present” in the ears after extended periods of listening due to the increased weight. in comparison, the Dunu model is a more ergonomic fit, and easier to put in a and out. It is also considerably smaller and lighter than the Campfire juggernaut.

Power requirements are heavier on the Dunu, requiring around 10 additional notches on the Fiio M11 in High Gain to match the Solaris in volume level. Both IEMs can be driven by weaker sources, but the DD drivers in both respond better to a higher current/higher output source.

Build quality is a draw, with both IEMs being manufactured impeccably. Packaging is again more or less a draw, with the Dunu presentation being more ostentatious but both coming across as definitively “high end” in terms of both feel and accessories. The cable is probably just edged out by Dunu – the quality of both included cables is definitely at aftermarket levels, with neither requiring replacement with a better looking (or sounding) cable as standard, but the Dunu replaceable jack system just offering a shade more functionality. I also prefer the Dunu earguides over the use of memory wire in the CA SuperLitz cable – CA have moved away from memory wire in their latest Polaris2 and Io models, so I’m hoping future iterations of the SuperLitz will get the same treatment.

As stated initially these two IEMs are more similar than different, both presenting a hybrid sound with definite weight in the low end, but with a surprisingly coherent overall signature and a lightness and speed in the low end. The Dunu comes through as the crisper and lighter sounding IEM, trading blows admirably in detail and clarity. The Solaris edges it for me overall with a far better sense of imaging and a slightly warmer and more substantial physicality in the low bass, but both IEMs are definitely not a million miles away from each other in overall signature, and certainly not in technical prowess. As mentioned, this will come down more to signature preference than a battle of which is “better” (unless you really need an IEM with a holographic staging, in which case the CA wins there) – if I had to pick just one, I would choose the Solaris, but it would be a much closer decision than I initially thought. Considering the price difference, that is a pretty impressive statement for the Dunu.

Final thoughts

Transitioning from mid-fi to the more rarified atmosphere of the “Top Of The Line / TOTL” section of the market is always difficult for any established manufacturer, especially if they have previously made their name with “bang for buck” models that competed well in the perceived value for money end of the marketplace. Will the customers follow you on to bigger and better things, and will they accept the inevitable increase in price tag that comes along with it? Ibasso have successfully managed it, with their transition from value DAP manufacturer to their success with the IT04 in-ears and DX200/DX220 models recently. Can the DK-4001 springboard another Chinese manufacturer into the “big leagues”?

In Dunu’s case, the answer should be a fairly resounding yes. They have managed to produce an IEM that can happily go toe to toe with some models costing almost twice as much in both resolution and overall clarity, with a mature and well thought out tuning that brings together the best aspects of the oversized dynamic driver and the high-range prowess of the quad-BA setup to form a clean, neutral sound that still manages to remain musical and engaging.

Everything from build to design to packaging screams that this is a labour of love for the company, and a genuine attempt to make the best-performing IEM that their design and manufacturing teams are capable of producing. This is the epitome of a “grower” – it isn’t a signature that will immediately blow you away with its bass, or stun you with treble sparkle, but over time, you appreciate that this is a sound that is accomplished, technically very proficient and more than anything else, just listenable. It straddles the line between analysis and enjoyment extremely well, and offers something a little different to the typical raft of V or U shaped IEMs doing the rounds in the $1k+ market. Throw in a cable connector system that has been well thought out and brilliantly implemented and a raft of additional niceties like the leather case and multiple tip choices, and you have something that is well set to compete with anything currently out there in the sub-$1k market, and plenty of IEMs costing considerably more than that.

As always, this isn’t a flawless victory, and there are some things that I think the DK-4001 could possibly improve on. Imaging is merely middle-of-the-road in the TOTL bracket, so those looking for a hyper-real sonic stage image and the ability to lock each musician down to the exact GPS coordinates in the soundscape will probably be better served looking elsewhere. The bass, while well judged, could stand to be just a shade heavier and more impactful from the huge beryllium DD, and the high-mid peak could possibly be pulled back just a fraction. None of these gripes (well, more nitpicks really) have stopped me for enjoying the DK-4001 for exactly what it is, though: a well tuned, musically enjoyable and hugely technical IEM that marks Dunu’s first entry into the top tier of in-ear audio. If this is a sign of things to come from the Chinese manufacturer, the future should be very bright.

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