DUNU-TOPSOUND DK-4001

Disclaimer
The DK-4001 is a loan sample and has to be returned. No incentive was given for a favorable review. This review is my honest opinion of the DK-4001.

Listening notes
I spent approximately 60 hours with the DK-4001, listening to Cayin N6ii (A01 and T01 motherboard) with the stock Dunu Noble cable and the Hansound Zen 8 wire both using balanced 4.4 plug.

Special thanks
For some reason, I have meant to try a Dunu product for a while now but never blind purchased one as I had very few opportunity to audition the gear even in Paris (this is going to change soon) and it actually was how Dunu set me up with a demo. Kudos to the Dunu team for taking community feedback into account and proactively contacting me to fix that situation. Thanks to Dunu for also helping me make the French Review Tour a reality and provide a sample demo of the DK-4001 and DK-3001 Pro.


Packaging and accessories

• Plug *4 (2.5 TRRS, 3.5, 3.5 TRRS, 4.4 TRRS)
• Aircraft plug
• 6.35 plug
• Cleaning brush
• SpinFit silicone eartips L/M/S*2
• Gray silicone eartips L/M/S*2
• T500 foam *2
• Leather case

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The Dunu DK-4001 packaging is quite premium, with a nice and compact leather carrying case. You can also find Spinfits CP145 and Comply tips, airline adapter and cleaning tools.

Worth mentioning is a « stock » cable that is more up to par with a very good upgrade cable as reflected in the price of the Dunu Noble cable (389$) that is provided with the DK-4001. A cable worthy of a flagship.



It’s a high-purity Furukawa Single crystal copper and pure silver braided cable. The cable features the fantastic interchangeable plug system that was found with the DK-3001 and continued with the Dunu Hulk. It come with 2.5, 3.5 single ended (and 3.5 pro balanced) and 4.4 termination. Note that Dunu added an additional interference-killing OCC copper sheath around the wires - a construction rarely ever seen in earphone cables. Interestingly, when I tested the Dun Lyre of the DK-3001 Pro, I noticeably picked up interference when running the N6ii with wifi on.

On top of this Dunu opted for their own patented catch-hold type connectors, « lowering connection instability and pin breakages, and effectively prolonging the service life of MMCX connector interfaces ». Catch-Hold® MMCX connectors are universally compatible with all standard spec MMCX seats which means upgrade cable are of course possible.



Specifications

• Driver Configuration:
  • 4 x Balanced Armature (Knowles)
  • 1 x 13mm Beryllium Dynamic
• SPL : 112dB @ 1kHz
• Impedance: 32ohm
• Frequency Response: 5Hz – 40khz

Fit, Build & Isolation
The DK-4001 fit is one of the best I have had with an universal IEM, it small, lightweight and ergonomic. The DK-4001 is one of a short list of IEM with a Zirconium shell, like Sony IER-Z1R. The use of Zirconium « effectively suppress harmonic resonance » according to Dunu.

Design wise, I like that the nozzle has a small ridge line to allow for deeper tip insertion, I didn’t need it but it can come in handy and reflects the ergonomic focus in the DK-4001 design. Included spinfits are really good and I didn’t need to do any tip rolling with my own tips. The over the ear cable configuration with preformed hook makes wearing the DK-4001 very secure. Isolation is good thanks to deep insertion and as usual for best results comply tips provide additional isolation.



Introduction
Dunu is now a well established brand in the audiophile world, which started as an OEM for famous brands. Since 2014, Dunu built its own IEM and now has a fairly complete lineup of dynamic and hybrid IEMs (Titan series, DN and the top DK series). After launching the DK hybrid series in 2015, Dunu set out to design the most compact, optimal shell fit that would define our flagship series. The DK-4001 says it has taken their head engineer Andy Zhao three years refining the acoustic formula, going through several redesigns before settling on its current form.

Dunu states : « We used two Knowles in tandem for four drivers in total, giving the DK-4001 the ultimate in treble headroom, and allowing its bandwidth to extend all the way beyond 40 kHz. To dial in the ideal balance between detail and harshness, we spent two months alone adjusting the tubing diameters, lengths, and damping materials, as well as the ideal crossover point for these tweeters. The result is a rich, luxuriating treble response pegged right where we want it to be. » About the dynamic driver, they state : « This 13mm speaker retains the speed and rigidity of a pure Beryllium cone, reproducing the kind of realistic timbre and wide staging that audio lovers crave. We allow it to sing freely by letting it take over the entire audio spectrum all the way to the low treble, reproducing music truly the way it was meant to be heard. »



The product page on Dunu’s website doesn’t expand too much on the DK-4001 tuning except from exceptional bass control deriving from Zirconium properties and the acoustic design through their patented ACIS which is a spiral design pathway : « To take full advantage of the speed and dynamics of the Beryllium driver, we wanted to take on the challenge of integrating a bass reflex system normally found only in home speakers. After long hours and endless trials tweaking its length and size, the resultant, labyrinthine Air Control Impedance System (ACIS), was born from an obsession that nearly spiraled out of control. The end result is a spectacular bolstering of frequencies under 80 Hz while still retaining depth and agility. »

Clearly, Dunu invested a lot into the design of the DK-4001 : materials with the zirconium, acoustic design with ACIS and tubing and damping of the Knowles drivers, coating of the beryllium driver. How does that translate in terms of sound quality? Let’s see !




Sound
The very first minutes into auditioning the DK-4001, the first thing that came to mind was how good the bass was, as in definitely top tier good : Dunu certainly has found a superb balance between engagement and technicality there. The second thing that came to mind was that detail retrieval : very very good, but maybe a tad over accentuated upper treble for my taste reaching the edge at times on some recordings. Not unforgiving, just a tad to present upper treble peaks for my taste and limiting the naturalness of the DK-4001. This was even more apparent with the T01 motherboard for the N6ii so I kept the A01 on for the rest of the review.

I began suspecting the silver in the Dunu Noble cable was maybe not in the line with my personal preferences and despite its stunning build and fantastic form factor I should try something different. Unfortunately my Dunu Hulk is 2pin so I couldn’t test that. I swapped the Dunu Lyre which is also a full copper and… the result was much more in line with my personal preferences. I found the DK-4001 gained musicality and didn’t have any peaks in the upper register as well. Sure, the Noble provides greater detail retrieval but to me at the cost of too much upper register emphasis, taking the attention away from a beautiful midrange. I then tried on a Hansound Zen full copper 8 wire cable and… the DK-4001 soundstage expanded to holographic territory with better imaging and layering. Obviously your mileage may vary and not everyone has the same preferences. This speaks to the scalability of the DK-4001 as well, which shows that it has great potential to fit your personal preferences.

The soundstage is not massive like say Campfire Solaris but it’s pretty good nonetheless, quite wide and fairly deep but not very tall. The image is not congested and remains articulate but separation is not accentuated, the image is more of a continuum while not falling into the wall of sound category. Vocals and lead instrument are clear and distinct, but not significantly forward either. Note attack is snappy and decay is very natural.

I didn’t find the DK-4001 hard to drive and the N6ii was set on low gain at fairly moderate level (35-50/100). I suspect though that the DK-4001 could reach yet another level with an amp, I see the DK-4001 having good scaling potential with its 32ohms impedance and dynamic drivers usually like power.



Bass
Note : The DK-4001 bass was great right out of the box but got even better with burn in with things settling in nicely after 40 hours or so. The main benefit is tighter bass with better control as the beryllium driver settles in.

The DK-4001 bass shows that Dunu’s R&D and work on acoustics of the shell (ACIS), optimized resonance with Zirconium and driver coating certainly paid off as advertised on their product page. The bass extends deep and exhibit fantastic control with very low resonance indeed. This is especially stunning on sub bass : there is plenty of subs but close to no distorsion whatsoever the subs are as clean as I have heard them.

This results in one of the best if not the best portraying of bass I have heard to date. This is an experience not unlike the legendary Sony EX-1000 with bigger than life bass that sure rarely belong in an IEM but rather in good closed back full sized headphones and not often with that level of control. Impressive if you factor in that it’s faster than the EX1000. Mid bass have great slam factor and remain clean and controlled whatever I threw at them. Despite its relatively big size (13mm) the beryllium dynamic driver is quite fast with quick decay and recovery time, providing a very good sense of pace.

The DK-4001 bass make the DK-4001 a very engaging listen, bass guitar have good weight, kick drums have such a satisfying, toe tapping punch and there is a physicality from the subs that make the DK-4001 a very powerful IEM that almost sounds like a full sized headphones.

This is class leading bass performance with a touch of basshead pleasure, although I don’t think pure bassheads will find the quantity to be enough. Dunu strived to keep the DK-4001 in the flagship category meaning it shows proper restraint and does not overdo it. But you can feel that given the right source, right EQ and right cable the driver probably has basshead potential for those who would want to go down that route.

Mids
The DK-4001 mids are not as warm as those featured on the DK-3001 Pro and more in line with what you would expect from a flagship : natural sounding with good tonal balance and articulate image.

Given the strong bass presence Dunu wisely kept the lower mids on the leaner side gently rising from 600Hz and topping a little before 2kHz. For the same reason given the treble presence, Dunu rolled off the upper mids from 2kHz to 4kHz where it reaches its lower point and then a rise to plateau at 6kHz up into the treble section. Clearly, the mids presence is derived from the 1-2kHz range. This results in mids that give instruments a slightly forward placement but avoiding too much excitement, attack on percussive and rhythm instruments is on the softer side.

The DK-4001 excitement is focused on its bass and treble but the fairly neutral mids are placed a bit forward to balance the overall frequency range and avoid a U shaped signature. A wise choice as too much lower mids would have resulted in a warmer signature (aka DK-3001 Pro as we will see in an upcoming review) and too much upper mids would have made the DK-4001 a very fatiguing IEM. On the flip side, this affect the bass guitar snap, the saxophone bite or energetic cymbals « clang » for example.

Treble
It’s very clear with the DK-4001 that Dunu aimed at a different goal than the more « mainstream » (this is in a good sense) DK-3001 Pro. Flagship often equates to resolution and definition, by way of more upper treble presence among other things. I believe this also explains the choice of a copper-silver mix in the Dunu Noble cable that comes stock with the DK-4001. As I hinted before, this clearly boost the upper treble section and make the DK-4001 detail retrieval greater but it also was a source of frustration to me as it kind of broke the naturalness of the upper register. For the rest of the review, I alternated between the full copper Dunu Lyre and the Hansound Zen 8 wire that both brought a more natural tone and smoother treble presentation.

The DK-4001 has good lower treble energy with a 6 to 8kHz plateau, snare drums have a satisfying snap and Piano, hi hats and cymbals have nice overtones that contribute to the musical engagement the DK-4001 provides. Despite the energetic lower treble, the DK-4001 manages to remain smooth and never harsh. Treble tone is accurate, and the note weight is quite balanced it’s neither a full bodied nor a feather like treble but rather very natural sounding notes.

Upper treble roll off steeply between 8 and 10kHz with a steep rise past 12kHz up to a 20kHz peak. The DK-4001 has good resolution and air and never feels congested but to me it’s not up there with the best here in terms of sheer resolution and refinement.


Verdict
The first contact with a brand is usually a good way to measure the quality of their product and upon my contact with the Dunu Hulk I was very impressed that a 300$ cable was built better than some products 3x as expensive not even taking into account the fantastic interchangeable plug system. It was just as impressed with the DK-4001 from the unboxing to the superb build and cable and the great fit.

In the very competitive hybrid universal landscape, the DK-4001 stands proud as a proper flagship product the Dunu brand packed a lot of R&D into : zirconium shells are notably hard and costly to produce (and featured in much pricier IEMs), driver coating process, and acoustic research (ACIS, tubing, damping...) clearly paid off especially in the bass department. The effort was furthered by packing the best build on a stock cable I have ever seen in a product and a very rare instance on the market (aside from LCD-i4, I don’t know of other examples of such premium stock cables).

All in all, you’d be hard pressed to find a competitively priced hybrid that packs as much R&D and premiums materials and cable, bar the Sony IER-Z1R priced over twice the DK-4001. This tells you something about Dunu’s commitment to grow their product range.

If you’re looking for a hybrid with superb build and cable, class leading bass (I am thunderstruck!) that is both fun and technically faultless, natural mids with slightly forward vocals and lead instruments and exciting treble then you’d be hard pressed to find a better alternative than DK-4001 for the price!

If you’re willing to sacrifice a bit of bass control, overall technicalities and like a warmer tone and smother presentation then its little brother the DK-3001 pro is definitely an alternative worth looking at. If you’re willing to spend a bit more, the Rai Penta will be airier with greater soundstage and imaging but you won’t get the satisfying bass experience or the body and weight you’ll get from the DK-4001. You could also satisfy your inner basshead and go to Campfire Solaris to enjoy massive soundstage, subwoofer like sub bass and sparkly lower treble but you won’t get the same control and balance as the DK-4001. In the technically proficient category, you could get a look at StealhSonics U9 to get further refinement in the upper treble section and more detailed mids but you would miss out on the incredible DK-4001 bass experience and you wouldn’t get the same bodied presentation.

I must say I am very eager to see what Dunu will come up next with the DK-4001 Pro and any other product for that matter!

https://iem.reviews/2019/11/03/dunu-dk-4001-thunderstruck/​

Dunu DK-4001 Chi: Perfect Fusion

A reputable IEM brand, Dunu finally came up with the long-awaited product - the DK-4001. It's been delayed a lot more than we expected and there are good reasons behind it. We'll be going through about these stories as we progress with the review. DK-4001 is Dunu's current flagship model retailed for $899.






Packaging

The packaging has gone through some changes too, now coming with a high-class packaging and presentation. As you open the box, the first layer is covered with a protective sheet, containing the earphone, stock cable, and 2.5mm / 3.5mm balance / 4.4mm jacks.






The second layer contains a leather case, aircraft plug, 6.35 plug, cleaning brush, 4 pairs of Spinfit tips, 3 pairs of silicone tips, 1 pair of Comply foam tip, and a leather case, and two paper works that describes the specs and tech behind the product, each written in English and Japanese.






Earpieces - Design

The earpiece shape of DK-4001 has a similar form factor as the DK-3001, though a whole lot more ergonomic. The nozzle length and angle have been adjusted, providing a more secure fit. The inner part of the shell has been modified, now having a smooth and simpler round shape which sits comfortably in the ears without a problem.

It has been an ongoing topic throughout the communities that DK-3001 were uncomfortable and saw many who had to give up using them for its problematic fit. While I personally haven't found the fit to be an issue from it, without a doubt DK-4001 provides a better fit as well as a deeper insertion. The housings are made of zirconium liquid metal alloy, just as the Falcon-C does. The MMCX connectors also seem to be replaced with new generation sockets, providing a stronger yet durable connection.






Earpieces - Drivers

DK-4001 features 4 BA drivers and a single 13mm beryllium dynamic driver, both sides coated with PVD. I've found it interesting that these, having 4BA+1DD configuration, are set to be only 2-way. Turns out the dynamic driver covers from ultra lows to upper mids, while all four BA drivers are tuned to work as super tweeters for high frequencies. It's pretty much a dynamic driver powered IEM, augmented with multiple BA drivers.

For a little more elaboration, dynamic drivers make sound by vibrating the diaphragm. Though this easily results in an issue where the middle and the edge of the diaphragm start to show differences in frequency production. Manufacturers overcome this issue with various solutions (Hifiman's Topology diaphragm, AZLA's Infinity ARD, Campfire Audio's ADLC diaphragm, etc..) and Dunu decided to solve this by substituting in with BA drivers instead.

Dunu also applied a spiral-shaped vent path in the inner part of the faceplate which could achieve deeper bass response low as 80Hz. Enough with the talks behind the product, let's now talk about the actual stuff.






Cable

The cables got more serious too. It's stranded with 7N copper and pure silver wires with a modular plug system, Quick Switching Connector. Dita was first to apply such feature with the Awesome Plug, though convenience is the difference.






Dunu's Quick Switching Connector

Dita's Awesome Plug required screwing in and out for replacing connectors, however with this one you simply pull it out for detaching and push it in for installing. It's significantly faster and it doesn't detach on its own either. I also like that they've included a variety of jacks, including the 4.4mm and 3.5mm balanced terminations.






Sound impression - Lows

Strike and decay are fast and leaves only a minimum amount of reverbs, just enough to maintain the natural representation of the bass. Though this happens along with the ultra-lows being clearly visible, making the overall bass very dark in color without bloating the quantity. The bass feels like it has been matured from a distance until arriving at the ears, presenting a natural sound flow. DK-4001 proves it well how to create heart-rumbling bass without excessive quantity. I'm sure it would be hard to find such clean ultra lows without boosting the quantity.






Sound impression - Mids

The bass extension was amazing, but the real amazing part happens from the mids - it retains much of the characteristics from the dynamic driver while bits of BA characteristics "submerged" into it. It's a new type of characteristics and presentation, so it's quite hard for me to exactly elaborate the feeling.

This perfectly fused hybrid system even left me confused for the first several minutes auditioning to DK-4001. There's barely any gap or sense of difference found between DD and BA drivers. AZLA-01R also done a great job fusing BA & DD by incorporating Dynamic Motion's 'Bull's Eye Driver', but DK-4001 goes even further with the driver numbers, as well as achieving superior excellence, maturity, and performance. Definitely a new experience.

Characteristics, textures, and tonality of mids are mostly dominated by the dynamic driver. There is a glimpse of BA-ish texture and feel from the upper mids but doesn't fall much apart from DK-4001's mainstream tone - in fact, this is the usual Dunu coloring that they slightly add to their most IEMs. Sounds crunchy and resolving, but doesn't fall behind in tonality that much. Mids are slightly placed forward and feel energetic. Compared to DK-3001, it has a wider sound flow and shows significant improvement in resolution. Sibilance is fairly well controlled.

It occasionally makes a slight hiss on the upper mids but doesn't get too sharp or spiky. While it isn't too harsh, this still means that users who are into fatigue-free sound are out of luck. This is something that adds a resolving characteristic to the mids and shouldn't be an issue if you're relatively used to bright sounding IEMs (similar or slightly lesser than DK-3001). Vocals have neutral thickness but tilt a bit to the thicker side.






Sound impression - Highs, etc.

Trebles go for similar characteristics as the mids - shiny, bright, and resolving. Though the reverbs from the treble have been controlled with faster decays, so it doesn't get much hot or irritating. Plus, the soft texture from the lows and the dark background neutralizes the bright, shiny upper frequencies. Trebles have more airiness and approach closer to the ears. Soundstage and imaging definitely head for the flagship level, leaving no doubts with its superiority compared to the DK-3001. Not only the wideness and the 3D presentation has been improved, but also the depth.






Eartips / Cable matching

Dunu spent lots of attention on their cable and eartip selections. The included Spinfit eartips are specially optimized for DK-4001 in terms of both comfort and sound. These eartips have wider bores and slightly shorter stems, less interfering the original staging and bringing the mids a lot closer than ordinary silicone eartips. I usually prefer JVC Spiral Dots as my eartip selection and also did with my DK-3001, though these customized Spinfits provided the best matching among all. Cables are also well matched with these earphones, not lacking in performance compared to other quality custom cables. Copper cables seem to show the best combo and I'm sure Dunu's Hulk cable will work fantastically with these.






Verdicts

DK-4001 is a precisely constructed IEM upgraded from DK-3001 in all aspect. It's interesting to see Dunu applying all kinds of unique structural tuning to create this IEM, but of course, it was to aim for the best and I could also agree to that. It's evident on the product that they've done their best to create a seamless product, starting from the sound to minor details like switchable plugs and customized spinfit eartips. DK-4001 would fit well for those who are looking for a rich w-shaped sound with shiny upper frequencies and would, of course, be a perfect choice for prior DK-3001 or Falcon-C users. Well done, Dunu!

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Dunu DK-4001 has been purchased by myself.
I am not affiliated with Dunu and none of my words were modded or asked to be changed.​