Headphoneus Supremus
Dunu Zen Pro – The Delicate Sound of Thunder
Pros: Uncommonly well balanced sound
Magnificent timbre top to bottom
Muscular & ballsy sound signature across the board
Deceptively powerful & well extended bass
Wonderfully coherent
Class leading technicalities across entire FR for a single DD
Holographic sound
Forward present & well bodied midrange
Beautiful & complete accessories packaging
Possibly my favorite stock cable ever
Cons: Source sensitive-- can come off a little harsh up top in lower mids/upper treble with some sources
Some reports of a metallic tinge on the timbre-- though this seems to vanish with some sources
Not as well extended or detailed up top as some sets
Dunu Zen Pro – The Delicate Sound of Thunder

Preamble: My Zen Pro was purchsed by me from Amazon. There was an open box discount but I was not asked or required to review it. This review is motivated by nothing other than my wanting to express and share my regard for this IEM.

Today I am reviewing the Zen Pro, a single DD IEM from Dunu. Dunu is one of those companies I’ve long been aware of through positive impressions I’ve heard from friends of IEMs like the Luna, SA6 and earlier models like the DK3001. However given that I live in Canada-- comparatively an IEM wasteland relative to many other parts of the world— I am completely at the mercy of whatever IEMs I can borrow through friends or hear through the rare tour I have access to. As it happens the Zen Pro is the first Dunu IEM I’ve had the pleasure to hear.

As is my custom whenever I do a review like this I begin with a preamble describing a bit about myself, my preferences and where I’m at on my own audio journey as, in addition to the satisfaction I derive from expressing myself in words, this gives potential readers a bit of background and context that will hopefully give a greater sense of where I’m coming from with respect to whatever IEM currently owns my heart—in this case the Dunu Zen Pro.

I have found over time that the scope of what I like or don't like can't be captured by a single target curve or tuning ideal-- my tastes, while definitely possessing some trends (a tendency towards DDs, for example), have evaded all my attempts to reduce them to a rule or small set of rules. I will say two things however—firstly that of all the main bands of the FR it’s the mid-range that I’ve started to recognize as the one I’m most fussy about. To wit: lately it seems to me that it doesn’t matter how good the bass, treble, technicalities and so forth are if the midrange isn’t to my liking none of it will matter.

Secondly, certain things—like perception of micro-detail—that often get elevated to the highest ranks of importance by the audiophile orthodoxy, has never been a massive priority for me personally. Accordingly I often don't rank IEMs noted primarily for their technical chops as highly as many others do. For me the most important thing, to put it bluntly and at the risk of inciting a few facepalms, is how the IEM in question makes me feel when I listen to it. I have a degree in mathematics & philosophy and teach the former for a living. I run a chess club and study great chess matches with intense interest and passion-- most of my life is focused on logical structures, rules, sequences, arguments and symmetries...and yet when it comes to music and this hobby it is 100% about feeling for me. When I'm listening to a great piece of music-- be it Barry, Coltrane, McCartney or Beethoven-- I am not reasoning or thinking or questioning or analyzing about who or what or how long-- I am having an experience, fundamentally, of the heart.

On that note let’s talk about the Dunu Zen Pro.

TLDR: Neutral & highly transparent sound with a hint of warmth. Blissfully coherent. Natural, bodied, balanced, dynamic, energetic & holographic sound. Impeccably technical & detailed, super linear, non-fatiguing though can be a bit vibrant in the upper mids depending on source. Beautiful timbre—to my ears especially with electric guitars, and horns. They're probably just on the "emotive over technical" side of the spectrum. Imaging & layering is top tier...staging is not massive but very layered & deep and everything is very well placed. Mids are even-keeled & clear, bass sometimes felt more than heard…but always felt, very well extended and reaches from the stygian depths. Treble is non-fatiguing, clear & decently extended. All in all the balance across the spectrum is wonderful. I don’t want to sound like a shill but holy balls do I love these IEMs. Listening to them through the AK SR25ii or Cayin RU6 and my heart is in want of nothing.


I’m not going to dwell too much on packaging & technical specs as it’s not really my style and that info is available readily elsewhere. I will say though that the Zen Pro come equipped with the most powerful set of magnets I’ve ever seen on a pair of IEMs. The magnets are so powerful in fact that if they get too close the Zen Pro earpieces will lunge and cling together. II’m careful to not let them do this though as even micro-impacts can damage the small drivers in these IEMs. I’m curious about the effects of the magnets however. I know that magnets are often a feature of dynamic drivers—growing up my buddy’s dad had a set of speakers with magnets so powerful they wrecked 2-3 of his TVs. Certainly they contribute to the sonic profile somewhere via the magnetic field they generate but I’m not sure how. The Zen Pro is notable for a very muscular & ballsy sound across the whole spectrum. The sound exudes weight, texture & authority—but not in an intrusive or belligerent way…rather in a seductive, well balanced and disciplined way. This muscular character is one of those intangible factors I’ve long been drawn to in IEMs without really zoning in on it as a particular point of interest. The only other IEM that has this quality to the same extent is the Dorado 2020—and indeed this is, I am finding, one of the main quality that has endeared me to this IEM. In the case of the Dorado 2020 I believe the hardness of the ceramic shell is what gives the sound it signature solidity and clarity—is the powerful magnet in the Zen Pro a different pathway to the same sonic character? This is something I will be looking into going forward.

Drawn together:

My understanding is that the original Zen was similar to the Zen Pro in many ways and has been refined due to some feedback they received on that earlier model. I had always heard of Dunu IEMs being notable for their bass and the OG Zen is probably the close I’d come prior to the Zen Pro to purchasing a Dunu IEM. What held me back at the time were consistent reports I’d heard of the OG Zen having too much energy in the upper mids—a consistent deal breaker for me. My decision to purchase the Zen Pro—in spite of the fact that I really didn’t need another IEM at the time—was based on a perfect storm of events consisting of some glowing reports I’d heard from fellow enthusiasts, the perpetual curiosity that afflicts all of us who regularly chase IEMs, my love of single DDs and long-held curiosity about Dunu. Couple all of that with the wind-in-one's-sails & opportunism that often attends finding a good deal at Amazon…and well the rest is history. I'm happy to say that my leap-of-faith towards the Dunu Zen Pro has turned into what is currently shaping up to be the definitive highlight in a year full of highlights for me in this hobby.

So how do they sound?

The Zen Pro put forward an impeccably balanced & exceedingly technical, bodied, dynamic, clear, detailed & spacious sound-- and the timbre is excellent across the board. Sound is forward and energetic-- these are not really what I'd call a relaxed listen per se. Guitars, horns, percussion, cymbals all sound perfectly natural to me. Guitars have both body & bite in nice measure. To be perfectly honest I never fully understood the appeal of neutral tuning until I heard these-- they are just so fun, engaging & satisfying to listen to and yet effortlessly technical, transparent and precise in their presentation. Everything feels so open with each element feeling, no matter how miniscule, is given its own clearly defined piece of the sonic tapestry in which to shine. I often classify IEMs as veering more towards an analytic (technical, detailed, precise) sound vs. a more fun & emotional sound. The Zen Pro strike as perfect a balance between those two qualities as any I have heard-- there is no excess and everything is represented perfectly and their ballsy dynamic sound is a constant pleasure. It was only after my initial musings of the Zen Pro that it occurred to me that the name "Zen" is perfectly apt for these IEMs. The Zen Pro is a little source sensitive and on more v-shaped or brighter players the upper mid/lower treble region can display a touch of harshness at times-- but for me it was minimal and this has been totally mitigated for me since using the Astell & Kern SR25ii and Cayin RU6 dongle. Synergy is a thing however it bears noting that this appears not to be an IEM you can plug into whatever source and get the same YMMV there.

Bass, Mids & Treble

The Zen Pro are some the most balanced IEMs I’ve ever heard. If you’re looking for a bass or treble specialist they may not be the best bet—the Sennheiser IE900 might be something to look at there. Alternately if you want something with more of a pure focus on the mids then the Oriolus Isabellae may be work checking out. Where the Zen Pro knocks it out of the park is how it manages to bring out the best and be totally satisfying across the entire FR spectrum. When listening to the Zen Pro I feel like am maximizing my enjoyment of the entirety of what I’m listening to to a greater extent than I’ve yet experienced with an IEM. As mentioned some have reported a touch of metallic timbre and harshness up top but in my experience if you get the right source this ceases to be an issue.

I am particularly impressed with the bass on the Zen Pro. It doesn't jump out at you at first-- and you might initially be tempted to think of the Zen Pro as bass-lite...which it isn't at all. It's super tactile & well defined-- and the extension is deceptively good. When the bass hits it seems to reach up from the murkiest depths-- it's a bit like the Odin this way and I would describe the bass on them both as reserved yet highly efficient, precise & powerful. Zen Pro’s bass is the sonic equivalent of Bruce Lee’s one inch punch. Sub & mid bass are, along with everything else, nicely balanced. A lot has been made about Zen Pro’s sub-bass roll off…but to me the graph is deceptive. Zen Pro’s bass has balls & weight—even when you don’t quite hear it there’s never any doubt it’s there.

Zen Pro’s bass reminds me of the bass on the Solaris...almost homeopathic in amount but the authority, weight & texture is spot on and it's subdued enough to maintain a sense of balance across the FR. I have many bass-leaning IEMs and it’s nice have one that's close to neutral...and a highly technical single DD to boot-- it's a big win for me. I think the ticket to the bass working for me is that it's got a nice sub -> mid-bass transition...the bass doesn't overwhelm but simultaneously it's warm and bodied enough that I don't feel anything is lacking. The bass on the Zen Pro is also much more technical and satisfying to my ears than the bass on the Solaris was. You’re not going to walk away after your first listen to the Zen Pro and go “wow! That bass!” like you will with something like the IE900 but after 3 weeks with these IEMs my awe of and appreciation for the bass on the Zen Pro increases daily.

The midrange is another highlight of the Zen Pro. It’s not as perfectly romantic, intimate and seductive as the midrange on the Isabellae is…but it is forward, clear, unveiled, layered, detailed and possessing of a wonderful natural timbre. In terms of vocals Mark Knopfler, Howlin’ Wolf, Morrissey, Fogerty, Sinatra, Sky Edwards all sound wonderful to me—bodied, full and clear. I’m not a particular expert on female vocals so I’ll defer discussing them…but I haven’t heard any issues. Instruments all sound full, dynamic, natural, detailed & clear. Of particular note to me are electric guitars (Knopfler’s strat has seldom sounded as good to me) but also saxophones—strings and horns in general.

Highs are (for me) adequately extended, clear and non-fatiguing. Highs historically have been the hardest things for single DDs to get right for me—often coming across as metallic, harsh or lacking in extension. Most of my favorite highs in IEMs come from IEMs with e-stat highs (like the Bravado 2 or Elysium) or with another type of DD (as in the IER Z1R). The highs of the Zen Pro don’t fall into the usual pitfalls for me, but they also don’t quite soar to the same heights (pun intended) as the highs on something like the IE900 do. What you get instead is a more even-keeled presentation across the spectrum.

Technical Chops

As I’ve come to understand the term “technicalities” are those features of an IEMs sound that allow it to create in the mind of the listener a fully vivid & realized head stage. Stage on the Zen Pro is not massive per se but is fathomlessly deep, layered and detailed. Imaging is superb with voals ever at the front and centre.. The Zen Pro is technical enough to satisfy those who usually pursue BA driven sets and the timbre is natural, thick and engaging enough for those of us who usually gravitate towards DDs. I was considering the word holographic with respect to these IEMs and in particular around what the word actually means. One of the characteristic features of a holographic image is that the entirety of the image is present even in tiniest part of it—in this sense while the stage certainly isn’t as massive as on something like the Campfire Solaris I do very much get that holographic feel from the coherent soundscape they present in that it doesn’t matter where I place my attention the entirety of the sonic spectrum is always to the fore—it’s a rather impressive experience and one I feel that to this point has not been fully captured on any hybrid setup.

As a rule the IEMs I gravitate towards aren't defined by their technical chops and I often wind up explaining myself in terms like "well I prefer timbre over technicalities anyway". The Zen Pro is remarkable in its ability to provide both bodied, natural DD timbre as well as, not just technicalities that "get the job done" but thoroughly impressive technicalities. I had no idea a single DD in IEMs could image & stage like this-- it's so deep and vividly and precise. Vocals are un-veiled, sibilance free and naturally seductive-- and the FR is smooth from top to bottom. While there is some sensitivity to sources with respect to some harshness up top and metallic timbre—on the right source like the Cayin RU6 or AKSR35ii— there is no fatigue, no peaks or pressure points to my ears though it must be stated that I do love a mice punchy, dynamic in-your-face sound as you get with many Campfire IEMs so YMMV there. For my own tastes I've never heard a single DD this consistently good across the FR.

Single DDs have the capacity to afford an amazing coherence—and the Zen Pro takes full advantage. The whole soundscape manifests as one cohesive, unified and entire structure of sound that, when coupled with natural bodied DD timbre, allows for us to be immersed in a sonic palace of natural grandeur and engagement that capture's both one's heart and attention in a way that hasn't yet been fully replicated in hybrid or non-DD setups-- at least to my ears. Traillii may be the only exception to this I've heard but I haven't yet spent unbroken days with one so ultimately the jury's still out on that one for me.

I think the outstanding feature of the Zen Pro from a technical standpoint is its resolution. I used to have a hard time talking about resolution because I wasn’t really sure what it meant and always thought of it as being synonymous with detail. In J Gordon Holt’s audio glossary he defines resolution as “that quality of sound reproduction which enables the listener to distinguish between, and follow the melodic lines of, the individual voices or instruments comprising a large performing group”—in other words resolution is in actuality a combination of things like detail and what I typically think of as “instrument separation”. Based on this definition I can assuredly say that the resolution of the Zen Pro is off the charts good and easily the best I’ve ever heard from a single DD. Through the Zen Pro every layer, every instrument, every performer manifests simultaneously with their own individual air, space and identity and also as an intrinsic part of a unified sonic tapestry. The more I listen to the Zen Pro the more I settle in to its fully realized, detailed, living, vibrant soundscape.


VS. Oriolus Isabellae

Compared to the Zen Pro Isabellae feels like more of a specialist-- more intimate, mid-range/instrument/vocal focused. Zen Pro by comparison is balanced across the board and it wouldn't surprise me if, once the dust settled, I proclaim it the best "all-rounder" I've yet heard. It doesn't quite sweep me off my feet and draw me into the mid-range like Isa does, and to be fair it's midrange on the whole probably isn't as emotionally evocative-- but the bass, treble and overall tonal balance & technical chops of Zen Pro is a decided step up from Isa imho.

I want to caveat the above statement-- one area where Zen Pro does shine above Isa is in the treble-- it has better extension and sparkle up top. Bass is about equal in quality, but tuned differently. It's not really fair to say that Zen Pro has a better tonal balance because I think that the goals were different with each IEM. Isa was never meant to be balanced across the FR-- it's about warmth and intimacy in the mid-range and it pulls this off marvelously. Zen Pro is more about balance and technicalities and it also pulls this off to great effect. On the whole each succeeds in its own area and I don't think it's really fair to say one is better than the other as they're like two fine but distinct wines. Zen Pro isolates better and is probably a better choice for a versatile all rounder. It doesn't romance me like Isa does, however.

Vs. Fiio FD7

From memory Zen Pro has a better tonal balance than the FD7 for me. I know some have described FD7 as "warm and bassy" but for me it was not that at all-- it achieved a tremendous amount of resolution up top but it achieved that by selling the low end short to my ears. Zen Pro does not have this problem-- it is very balanced and while there's certainly not a bass/lower mid emphasis or anything there is certainly nothing lacking there to my ears. The only ding in Zen Pro's armour for me so far is that it appears to be a little source sensitive-- the upper mids as has been mentioned straddle the line of being a bit too energetic at times…but with the right source and some time this seems to go away completely.

VS 7HZ Timeless

Timeless puts forward a presentation that is almost as balanced, more resolving, possibly better micro & macro dynamics. Timeless is an IEM that takes you by surprise with its naturalness whereas the Zen Pro is more in-your-face about it. In terms of engagement they’re probably about equal for me but Zen Pro is more energetic and in your face with that more bodied & ballsy sound…particularly down low…that other drivers just can’t emulate. Timeless is more effortless and natural…particularly through something like the Cayin RU6. Timeless is a shining star among releases this year but still has a couple kinks to work out—on its own terms little can touch it but it doesn’t quite lure me way for long from my favorite DDs like the Zen Pro. With the technology involved and the pace of innovation these days that day may not be too far behind.

VS Sennheiser IE900

My time the IE900 was very brief but it differs from Zen Pro in that, where Zen Pro is balanced & neutral the IE900 has a decided bass & treble specialty with the mids pushed back. IE900 has a tremendous reputation and in its own way it excels. If you want top tier bass & treble it’s by far the better choice—however if you’re looking for balance & neutrality in an all rounder the Zen Pro is worth a look.

VS Moondrop Kato

These are quite similar to the Zen Pro-- less balance, more tilted towards the bass, a lot less technical, more of a generic tuning. Not factoring in cost the Zen Pro eats them alive however when you consider that they only cost $200 or less than 25% of the Zen Pro they come off as a benchmark for the price tier they occupy. If you want an even keeled IEM that sounds good with everything, has no glaring flaws in bass, mids or treble, has more than adequate technical chops and you don't want to spend more than $300 then these are an easy rec. They're great for what they are but don't have any real standout qualities-- they don't have the balance of emotive engagement, impeccable tonal balance & technical prowess of the Zen Pro, or the divine mids and capacity for genuine intimacy of the Isabellae. They're a standout for $300 but they would not come close to tempting me away from the Zen Pro.


One of the most profound lessons I’ve learned in this hobby recently can be summed up in a quote by Steve Jobs—that I think I even featured in an earlier review in the year: “Sometimes you don’t know what you want until someone shows you”…how true this is. For myself I have found that whenever I try to really pigeon-hole my own preferences—which I thought I was on the verge of doing once I started really comparing the graphs of many of my favorite IEMs like the Duo, Dorado and Isabellae—along will come an IEM like the Zen Pro that throws all of that to the wind and completely reorients my own idea of what I’m looking for.

This brings me to another lesson—one so important that I’ve probably restated it in one form or another every time I’ve sat down to review an IEM: never judge an IEM by its graph. On two occasions this year—first with the Isabellae and later with the Zen Pro—had I gone just by the graph I would have never considered either IEM however upon listening to both I was instantly swept off my feet and smitten, albeit for different reasons. The point: ever be ready to try something new and always be willing to let your own ears be the final judge.

In closing I really want to emphasize the importance in recognizing the different approaches everyone may take in this hobby as they wend their way along the pathway to audio Zen (pun, again, intended). As hinted at earlier I often comment that there are two main ways to approach the listening experience with an IEM-- either intellectually or emotionally. The former implies looking at the different components of the sound through a proverbial microscope and the latter implies being more concerned with how one responds emotionally to the cohesive whole of the experience. Both approaches are valid however I think most people are skewed more to one side or the other. I like having a balance of different perspectives out there and so long as they're sincere they can all be helpful. As I said above my own personal bias is strongly towards the "emotional' side. When forming & writing impressions my inclination is much more towards the overall picture of the emotional experience of listening to an IEM-- and consequently when looking for impressions of others the number one thing I look for is someone having the same sort of emotional reaction to an IEM that I myself am craving...though I know some find this approach too wishy washy and not very helpful in much the same way that some find an overly analytical approach to be too devoid of the necessary romance of the experience. The beauty of this hobby and communities like this one is we have access to the full spectrum of different opinions and approaches and are free to take or leave what works for us or what doesn't.

Caleb Roseneau of Campfire audio in an interview I heard once described the main differences in BA vs. DD drivers being that BAs are better at "describing" sound and DDs are better at making you feel it. In light of the distinction I just made above DDs are more naturally suited to emotional engagement (evoking feeling) and BAs are more suited to intellectual engagement (being more detailed and technically precise). There is of course overlap but so far in my experience the best BA IEMs can't compete with the best DD IEMs in terms of sounding natural and evoking a certain type of emotional engagement and conversely the best DD IEMs can't compete with the best BA IEMs when it comes to technical skill and precision.

With the Dunu Zen Pro we have in my estimation a benchmark in the IEM world. It is a single DD that manages to take an extraordinarily balanced tuning and simultaneously imbue it with the bodied natural timbre one finds in a DD and a degree of technical perfection that, while certainly falling short of the most purely technical sets using BAs or e-stats—nonetheless leaves little to be desired. Dunu strikes me as one of those brands that have been quietly plying their trade for years...often below the radar. I never heard the OG Zen or any other Dunu for that matter but the Zen Pro, tuning wise, has the mark of a degree of polished perfection consistent with a clear vision and lots of experience. I'm feeling seriously tempted by the Falcon Pro just to experience more Dunu DD magic. The Dunu Zen Pro is my de facto IEM of 2021.

Samples of music used to generate the impressions used in this review:

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I see the Duo's in the picture, what cable are you using on those?