Fit and Comfort

There are subtle fit differences between the different ear tips that come with the DUNU ZEN PRO, at least for the same size. It's hard to see on the camera front-on, however. As such, I chose to show only one such size M ear tip installed on the right IEM, inserted into an artificial ear mold. I have average-sized ears, and the ear mold above represents my own experiences well enough as a proxy. Size M silicone tips are my go-to for testing since foam tips are not included by some, and I generally preferred the stiffer flange white silicone tips. You may want to consider using the foam tips for a better seal while potentially dampening the treble response, too. The size of these IEMS won't generally be an issue, being on the smaller side of average and adopting gentle curves courtesy the shell design that sits nicely supported in the concha as seen above. There is enough leeway to rotate the IEMs for better ear hook support from the cable, which helps since these are heavier than average at ~10.5 g each. With a proper fit, there was no physical fatigue. Indeed, I found myself using the ZEN PRO paired with my phone and the Type-C plug for a lot of things, including watching a few live sports events while on public transportation. Not once did I feel these were coming off either, and there is sufficient passive isolation, too.

Audio Performance

Audio Hardware

I went into detail on DUNU's ECLIPSƎ platform in the FALCON PRO review, which I won't repeat here. There is plenty new to talk about as-is, including with a dome that is far more sophisticated than the simpler amorphous diamond-like carbon coated composite polymer dome. The ZEN PRO ditches that in favor of a magnesium/aluminium alloy dome in a µ shaped morphology that is reminiscent of Focal's excellent dynamic driver headphones. As the FALCON PRO, the DUNU ZEN PRO dome is also coated with ADLC, but in a completely different process including reactor technology for a higher temperature coating that results in a more tetrahedral nano-carbon deposition, which is more in line with a diamond's molecular structure than coal. This also results in a more uniform coating, and everything combined, including the alloy composition itself, adds to the rigidity and internal damping of the ZEN PRO drivers.

There is a vibration-dampening ring and fully independent surround around the dome, and the magnets around the diaphragm are further optimized in orientation, shape, and distance from the dome to where over 1.8 T of magnetic flux are generated, which in itself is a record very few can even aim for. There are a few other tricks up the ZEN PRO's sleeve, or rather the front. Remember that cutout with the tiny holes in a long oval pattern? DUNU terms this the Air Control Impedance System (ACIS), claiming it assists lower frequency output (<100 Hz) while flowing well with the circular design of these IEMs. All this contributes to making the ZEN PRO relatively easy to drive with an average impedance of 16 Ω and 112 dB/mW sensitivity, though the company omitting the mW left me unsatisfied with their specifications sheet. This is plenty fine with mobile devices thus, and a portable DAC/amp will suit your needs perfectly for when you find yourself without an available 3.5 mm audio jack when on the go. As such, the digital plug options with DUNU's Q-Lock PLUS cables come in all the more handy here, with the integrated DAC providing enough power for the ZEN PRO. If stationary, the shorter cable included with IEMs might be a potential handicap when connecting to a laptop or PC as the audio source, especially with a standalone DAC/amp in the chain.

Frequency Measurement and Listening

I will mention that I have a general preference for a warm-neutral signature emphasizing a slightly elevated bass and smooth treble range with detailed mids and good tonal separation. I also generally prefer instrumental music over vocals, with favored genres including jazz and classical music.


Our reproducible testing methodology begins with a calibrated IEC711 audio coupler/artificial ear IEMs can feed into enough for decent isolation. The audio coupler feeds into a USB sound card, which in turn goes to a laptop that has ARTA and REW running and the earphones connected to the laptop through the sound card. I begin with an impulse measurement to test for signal fidelity, calibrate the sound card and channel output, account for floor noise, and finally test the frequency response of each channel separately. Octave smoothing is at the 1/12th setting, which nets a good balance of detail and noise not being identified as useful data. Also, the default tuning was used for testing, and no app-based settings were chosen unless specifically mentioned. Each sample of interest is tested thrice with separate mounts to account for any fit issues, and an average is taken of the three individual measurements for statistical accuracy. For IEMs, I am also using the appropriate ear mold fitted to the audio coupler for a separate test to compare how the IEMs fare when installed in a pinna geometry and not just the audio coupler. The raw data is then exported from REW and plotted in OriginPro for easier comparison.


The IEC711 is such that you can't really compare these results with most other test setups, especially those using a head and torso simulator (HATS). The raw dB numbers are also quite contingent on the set volume, gain levels, and sensitivity of the system. What is more useful information is how the left and right channels work across the rated frequency response in the DUNU ZEN PRO, or at least the useful part. The left channel was separately tested from the right one, and colored differently for contrast. I did my best to ensure an identical fit for both inside the IEC711 orifice, so note how the two channels are identical all the way through the lows and mids, and even the highs until well past the point where the coupler measurements need to be taken with a grain of salt. Suffice it to say then that I never noticed any channel imbalance at all even when specifically looking for it. These measurements were taken after ~50 hours of testing, and I noticed no change from hour one, where I had also done a quick measurement after some preliminary listening. There wasn't any burn-in effect, perceived or measured, with a mix of white/pink noise going through the IEMs for a good two days non-stop without changing anything. The response with the artificial pinna in place was basically similar enough to where I decided to forego it here given how long this page will already be.


This is the average frequency response for both channels of the ZEN PRO plotted against my personal target taken from VSG.squig.link, which also gives you an idea of my personal preferences to better correlate any biases possibly in play. The tuning of a set of headphones or earphones does not have to match my target as long as it is tuned with some direction, makes sense, and is executed well. After all, no one set will appeal to everyone, and having different options is what makes this hobby so interesting and hard to quantify simultaneously. What I can say based on my experiences with the ZEN PRO and other IEMs is that it is tuned well with a mellow V-shape, almost to the point of being warm-neutral, which appeals to me personally. But there's plenty offered to tug at many other strings too, so let's talk more about that now.

DUNU mentioned that it aimed to create a more balanced set of IEMs with the ZEN PRO, and address some of the lack of treble extension with the original ZEN. This makes me believe the ZEN was perhaps more V-shaped and got darker in the treble response, which others seem to agree with. This is not to say the ZEN PRO lacks bass; it has decent sub-bass extension even with the focus is on the mid-bass proper. This is where the FALCON PRO perhaps went a touch too far for some, but the ZEN PRO tweaks the elevation peak down ~50 Hz further, which is considerably more appealing universally I bet. When you have a single dynamic driver set, the bass response is where everyone expects the product's strength to lie. The ZEN PRO does not disappoint here, although I can certainly see a use case for a slight bass shelf on top. It takes EQ very well in this region, so go ahead and tweak it to your desire. For me, it was just about perfect as I prioritize energy, but not at the expense of detail. I care more about bass guitar notes than dubstep, and I want impact behind the delivery, too. The dynamics and technicalities of the FALCON PRO are why I was left impressed by it, and the ZEN PRO punches well above even that. Every strum along the guitar strings was well-appreciated, and this is where I can see fans of EDM and heavy metal preferring the ZEN PRO, too. Dynamics scale well with a bass shelf for tonality preferences, so that is where the ZEN PRO distinguishes itself from other V-shaped IEMs.

The lower mids are a touch too forward for my liking, but it does come about via a natural transition from the lows. There is no bloaty bass and bleed-over to affect, say, male vocals. I mentioned how I used the ZEN PRO with my phone on the go to watch videos outside of just listening to music, and vocals were a far more prominent aspect here. For some reason, I was in the mood for some life lessons from The Notorious B.I.G. during my testing of the ZEN PRO, and it was a good example of how forward-facing male vocals work out so well at times. There is very good separation between different mixed tracks too, and this is where I really got to appreciate these IEMs with the range in the mids. The technical performance does find itself wanting to an extent in the mids, however, with a narrow soundstage that reminds you this is stereo audio in your ears. Imaging is also inside around a 75° field in front of you for most sources, but such tracks as Low Roar's "I'll Keep Coming" showcase the left and right separation very well. Female vocals are tuned even better than male vocals, if you would believe it, and there was no point where I felt it was overly bright or shouty as we transition into the upper mids.

The in-ear resonance compensation is also well executed, but I should note that this is heavily subjective. As such, going with a slightly broader peak at 2–4 kHz is a safer approach. DUNU goes further here, but that is a natural extension of the tuning itself. Past this is where the weakness of the ZEN PRO is felt most. I can definitely see that the treble response extends further than before, but it is still easily bested by even all-BA IEMs that cost far less, let alone those with planar drivers or EST tweeters. To compensate for this, DUNU goes a touch overboard in the highs, but it ultimately makes the subsequent darker response come off flat. I will say that one thing it gets right here is timbre, which I have yet to see an all-BA set do well. The ZEN PRO treads a fine balance between a more hollow/plastic timbre and ringing/metallic one, with certain instrument classes getting their moment to shine without being compromised in this regard. Still, for most things instrumental, I'd probably look elsewhere.

Comparisons

This comparison is going to be weird because the other two have not even been reviewed yet, but I wanted to compare the DUNU ZEN PRO to two other IEMs with a similar tuning I have listened to and measured. The Lime Ears Pneuma is an expensive hybrid that has a bass boost switch, which was set to off for this measurement. The XENNS UP is a tribrid with EST tweeters, yet both of these manage to be similarly dark in the upper treble region. Okay, I may be extrapolating a touch here, but want to point out that successfully tuning IEMs for treble extension is not the easiest job in the world. Of the three, I'd definitely go with the ZEN PRO priced between the other two purely because of the better technical performance and excellent accessories, especially that cable. The other two are also much larger in size, which may make them physically fatiguing over time.


I would have loved to have more flagship-class single dynamic driver IEMs for a comparison, but the recently released FiiO FD7 never made it in for review, and I don't have any others here. Instead, I want to throw in a couple of other IEMs that are somewhat similarly priced but do things differently. The Audeze Euclid is priced higher and no longer enjoys the benefit of being the best-tuned planar IEM I have heard to date, which have been quite miserable to be fair. It fared well because of its technical performance, especially with bass macrodynamics as something I have only heard planar drivers do, but then came along the ZEN PRO to show a well-designed and engineered dynamic driver IEM can do the same. In fact, I daresay the ZEN PRO punches more so without lacking detail, and scales with EQ just as well within reason, so I would certainly purchase it over the Euclid, with the latter only besting the ZEN PRO in soundstage and imaging but then having a minimal treble response to begin with. The ThieAudio Monarch, on the other hand, is a better example of how to get treble extension with a tribrid configuration. It's tuned far more analytically than the ZEN PRO, making it more of a reference set amenable to mix with than simply enjoy music, and it has better resolution and timbre, too. Tuned differently from each other, the Monarch and ZEN PRO can't be compared easily, but I'd personally go with the Monarch, or maybe even the newer Monarch MK.2 that's supposedly even better.