DUNU Zen IEM Measurements and Analysis

Discussion in 'IEM Measurements' started by purr1n, Feb 20, 2021.

  1. purr1n

    purr1n Super Friend

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    Obligatory photo here:
    PXL_20210220_205957124.jpg

    Impressions here:
    https://www.superbestaudiofriends.o...ars-reviews-impressions-and-discussion.10501/

    Given the FR graphs floating around, I had initially thought I would run away in horror upon first listen, but this was not the case. The tonal signature is one that I would typically mock as stereotypical Asian IEM tuning with stronger than typical low-mid bass emphasis and a pushed up upper mids. However, I found the bass emphasis not overdone and a nice balance to the emphasized upper mids. What really drew me in was the timbre and articulation, particularly the decay of the drivers. The timbre and transient response was at least intriguing, something different, if not simply darn good.

    I had no idea what was in them as I intentionally avoid reading any marketing literature on IEMs because it's mostly dick wanking bullshit. What counts in the end is how they sound. (I could care less about 22 drivers, urethral openings, or exotic materials because 95% of the time, these speshal implementations sound like overpriced shit.) I thought the ZEN may have been a hybrid at first, but knew that wasn't quite it. Turns out it's a single driver magnesium alloy DD? Seriously, that's how lazy I am with respect to Googling.

    But of course! I thought I had recognized it - this from my speaker building adventures using the Seas magnesium drivers. The timbre is closer to these as opposed to the magnesium drivers of the Elear / Elex.

    In a nutshell, I'd say that the DUNU ZEN are like advanced JVC FDX1 with clearer lows and crisper highs. I have the FDX1 packed away so I cannot comment on things like bass texture, plankton, etc. I use the FDX1 with the blue filter or whatever filter is the least upper-mid forward one. The ZEN's tonal response, while stomachable for me, did leave my ears more fatigued than the FDX1.

    I don't want to crap on the DUNU ZEN's frequency response too much though. I get it, they need to make IEMs sound in a way that they think their audience, their customers will like. I just don't think that audience is SBAF. Would I say that it's a shame because there are such other strong qualities with the ZEN?

    Nope. Not at all. Most portable players have EQ. I also use Roon which has EQ. The thing about frequency response errors or screwiness is that they are correctable. This is why these errors are called linear distortion. Linear distortion can be corrected. Non-linear distortion cannot. Hence why my measurements will begin with non-linear distortion and how the ZEN performs well, or at least well in an interesting way very different from BA type drivers. When I find my FDX1 (the Pod has been delayed because of the weather related mini-disasters in Texas), I will do a non-linear distortion analysis of it for a DD to DD comparison.

    As an aside, I can hope that DUNU will make an IEM more tailored for SBAF tastes. The price is certainly right. I'd be creaming all over these if the FR were more like the Andro, Solaris, Ara. Really, I wish DUNU will make an IEM for people who did NOT grow up blasting IEMs at loud volumes so they have hearing damage between 3-6kHz.

    Usual disclaimer: as an American, I don't know shit about IEMs because there aren't any stores that carry 1037 IEMs that one can demo in North America. Not that it matters because 1031 of the 1037 are probably shit and out of the 6 ones that aren't, 3 cost like $4999. Personally, I'd rather spend that kind of money on a TOTL mattress and a nice bed.
     
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    Last edited: Feb 20, 2021
  2. purr1n

    purr1n Super Friend

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    Behold... the explanation of what I'm hearing is presented (and yes, I'm messed with you by not presenting FR first - because FR can always be corrected or tailored via EQ).

    The distortion plots below are plotted differently than what we usually see. The distortion is plotted at the frequency where the harmonic "activates", that is where we hear it manifest, as opposed to the fundamental frequency of the harmonic. I've only included the second and third harmonics and these two yield the most interesting results.

    DUNU ZEN Distortion Behaviors
    Alternate Visualization
    upload_2021-2-20_16-2-56.png

    $5 via paypal to the first person who can provide insightful comments. Hint: Compare to similar type measurements / visualizations in these threads:
    These measurements are rather more complex and involved - but they have high correlation to what I'm hearing.
     
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    Last edited: Feb 21, 2021
  3. shotgunshane

    shotgunshane Floridian Falcon

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    A single dynamic built like the Zen but tuned to SBAF tastes would be dynamic end game.

    3rd harmonics here look mostly good. Much lower than 2nd. What’s going on at 10k and above though?
     
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  4. Alondite

    Alondite Acquaintance

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    I wonder if that rise in 3rd up to and beyond 10k is responsible for the fatigue (though it seems like it would be fine at lower volumes because that rise becomes more significant in the louder plots, which also means they'd probably respond well to some EQ in this region). That would be my guess. Interesting that 2nd through the same region is almost like a mirror; it drops in a similar manner to how the 3rd rises. Also happens to be the only region dominated by 3rd, rather than 2nd order distortion.

    You noted that the U18t had "indistinct one-note bass," and the plots show 3rd rising higher than 2nd from ~200Hz down. Also, that it "tends to impart sort of its own timbre or overtones in the upper mids and lower highs," and the plots show 3rd rising higher than 2nd through this region.

    The Soranik plots are more similar than they different between 2nd and 3rd so I can't really glean anything interesting from that, other than them not having anything that is especially problematic.

    Seems pretty clear that having 3rd order distortion dominating over 2nd is no bueno regardless of where it occurs in the FR. Graphs are fun.
     
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    Last edited: Feb 20, 2021
  5. Friday

    Friday Friend

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    More BA-like treble due to higher 3rd harmonic distortion in the higher frequencies? Which might be why you thought they were hybrids (and not necessarily in a good way)?
     
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  6. purr1n

    purr1n Super Friend

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    Here's the more traditional distortion plot for another perspective. This plots the distortion to the fundamental.

    DUNU ZEN Distortion Behaviors
    upload_2021-2-21_6-34-38.png

    I do wonder if the rise in the third harmonic is associated with both the fatigue and at least some of that magnesium driver coloration. I mentioned that the this DD sounded more like a Seas magnesium driver, in particular the W15CY, than the mag alloy driver in the Elear.

    I pulled this up from zaphaudio, which is the distortion measurement for the W15CY.

    There is one similarity here. Both the Seas and the ZEN have a sharp rise third order distortion from 2kHz onwards (the ZEN's extends and peaks a bit further).

    upload_2021-2-21_6-55-35.png

    upload_2021-2-21_6-53-57.png

    One thing to note is that the W15CY driver can also be fatiguing if used past 2kHz. (It should be crossed over with a steep slope IMO - speaker builder guys tend to be a lot more fussy than headphone/IEM guys about colorations like this).

    The thing about the ZEN measurements is that the third-distortion hump only manifests at higher SPLs. I do listen loudly, and with the ZEN's upper-mid forward frequency response, it's likely the H3 behavior will be heard. Of course the good news is that maybe with EQ correction to push the upper-mids down, this fatigue problem or metal coloration goes away. This will definitely be worth investigating.

    Indeed. This could be why I felt it had hybrid like qualities, that is DD on the bottom and BA on the top.
     
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  7. purr1n

    purr1n Super Friend

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    Despite, the H3 rise in the highs, I was rather smitten by the timbre of the ZEN. A few things to point out.
    • The second harmonic, H2, is a bit lower than the H2 on U18T at higher volumes, but quite a bit higher than Ara across the board.
    • H2 quite good. There is a rise in lower frequencies similar to speaker drivers, but otherwise the H2 is flat across all frequencies with the exception of a small bump near 3kHz.
    • H3 is quite a bit lower than both U18T and Ara (both BA type IEMs) - with the exception of the 2-6kHz rise at higher SPL. Does this account for something about DD bass sound or DD texture?
    dunu dist.gif
     
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    Last edited: Feb 21, 2021
  8. Augmentin

    Augmentin MOT - DUNU IEM Company

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    Thanks for the analysis @purr1n --- just a few things to remark about this model. It was designed essentially like a miniaturized Focal driver, but the geometry of the dome was adjusted to suit f0 for small volume cavity. The driver was designed for essentially one main goal: good macrodynamics. So it combines a big dome with a really compliant surround. But because of the increased moment of inertia of the Mg dome at this size, the driver will begin exhibiting non-linearity at high frequencies, which will account for what you're seeing in the odd order harmonic distortion. We have a dampening bushing inserted between the dome and PU surround, but it doesn't completely eliminate the rise in non-linear motion. The issue would be mitigated if we used a less compliant surround like PEEK, but then it'd just be another driver and we could just use anything off the shelf. Or, a smaller size driver would have addressed both the NLD and FR issues brought up by some people, but this was a retrofit design to fit the body of a housing originally designed for this diameter.

    Driver_ZEN_Diameter_02_Small.jpg

    As for tonality, it's always a compromise. The company's core audience in China likes upper mids. I've been pushing to fork tunings for different markets but it's not something that will happen overnight. It's also much harder to do alternative tunings for single DDs. The housing is coupled with the driver, and a driver dome would need to be redesigned for this to happen. Or, Helmholtz resonators would have to be machined into the housings. This means the housing needs to be made on a future-proof platform to account for the machining of resonance chambers in advance. Doing things like adding acoustic output impedance with foam/cloth is more of a band-aid and isn't really going to correct things that were problematic to begin with. It's basically physical EQ. Lastly, it's not actually easy to design a single DD; hybrids and BAs are much easier because so many FEA modules have been developed to allow for virtual rapid prototyping these days. Single DD virtualization tools are far less robust.
     
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  9. YMO

    YMO it's not drinking alone if you're on Zoom

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    This was my biggest issue with the Zen, which is why I prefer the SA6. If it didn't have this issue where everything becomes too loud and fatiguing, I would pick Zen over SA6.

    I don't have this problem at all with my JVCs, which is why it is my daily driver on the IEM camp.
     
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  10. jaker782

    jaker782 Facebook Friend

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    Nice analysis here. So it seams the Zen is a very capable IEM technically, but tonality is a little off, at least for generalized SBAF preferences. Have you had a chance to test out the SA6? I am curious what you think of that model as it seems while not quite on par resolution wise with the Zen, it has a more agreeable tonality and "special sauce" so to speak and is the preferred model based on the impressions thread, especially when price is considered.
     
  11. purr1n

    purr1n Super Friend

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    DUNU Zen
    Impedance (and electrical phase)
    upload_2021-2-23_16-53-27.png

    Mostly flat. Two bumps exactly where I would not want them since the Zen is already midrange forward enough. However, the dumps are not extreme. Nominal impedance is about 17-ohms with the highest bump around 4kHz at a little above 20-ohms. That's nothing really.
     
  12. Kunlun

    Kunlun cat-alyzes cat-aclysmic cat-erwauling - Friend

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    YES PLEASE

    YES PLEASE

    HELL YES PLEASE
     
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  13. purr1n

    purr1n Super Friend

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    Multiway DD? Big DD for lows. Smaller DD for highs.
     
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  14. purr1n

    purr1n Super Friend

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    Now on to frequency response. Really good channel matching or I got lucky.

    DUNU ZEN
    Frequency Response
    GRN = left, RED = right
    upload_2021-2-25_19-22-24.png

    DUNU ZEN vs. FDX1 w/ Blue Filter (YEL)
    Frequency response
    upload_2021-2-25_19-24-2.png

    And this last one is for you @rhythmdevils:

    DUNU ZEN vs. Campfire Audio Ara (WHT)
    Frequency Response
    upload_2021-2-25_19-24-52.png
     
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  15. purr1n

    purr1n Super Friend

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    This is what I did for EQ. I used the frequency response measurements as a rough guide - a starting point. Then I tweaked the parameters by ear. I didn't spend too much time on it. The settings are in the image below.

    upload_2021-2-25_19-32-7.png

    • Note that I do not believe in surgical EQ - it unnecessary and overly complex. Lots of EQ also means more processing, greater latency, and more oddball phase shifts. With music, we won't make out anymore more granular more than 1/3 octave.
    • My general approach is to fix things with no more than x3 parametric EQ. Anymore more means the transducer is beyond help, or that you suck.
    • I preferring cutting instead of adding gain. Adding gain means I need to lower the overall level thus losing dynamic range, increasing noise, and increasing distortion in a region where the transducer is already having a hard time getting loud enough. Where I do add gain, I prefer to add no more than +3db.
    Note that the high EQ was an experiment to see if I could get more air / top octave after the initial three settings. It didn't do much so I just turned it off. One of the downsides to the EQ above was that the lack of top octave became very evident. This makes sense because the "Asian" EQ tuning with massively emphasized upper mids and lower treble basically masks any mid or high treble.

    Below is the resultant frequency response after EQ. The sound is subjectively less bright than what is objectively measured. Frequency response does not explain everything! This is why Amir did not like the small ELAC (with the metal dome tweeter) which measured perfectly.

    DUNU IEM
    Frequency Response
    After PEQ
    upload_2021-2-25_19-42-6.png
     
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  16. purr1n

    purr1n Super Friend

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    And here is the DUNU ZEN's distortion with EQ applied (at 104db SPL) to compare directly with the distortion with EQ applied. The distortion is much lower in the problematic 2-6kHz region

    The makes total sense. The driver isn't working the bass as hard - excursion will always negatively affect distortion everywhere. Much of the distortion from driver breakup in the highs is gone.

    DUNU ZEN
    Distortion
    EQ correction applied to FR
    upload_2021-2-25_19-51-25.png

    DUNU ZEN
    Distortion (no EQ, stock)
    upload_2021-2-25_20-1-14.png

    Closing thoughts:
    1. The DUNU ZEN is fantastic if you are willing to apply EQ. The sound is clean. The distortion behavior, with higher second harmonic over third is more "normal" sounding than BA type drivers, and the reason why there are many DD proponents.
    2. Very dynamic - lets loose - especially with better gear - see below.
    3. The midrange resolution is utterly fantastic. The ZEN has a "fast" DD driver like the Focal headphones. As such, the ZEN scales like mad with better gear. It will scale much more with better DACs, amps, from desktop systems vs. portable stuff.
    4. The lack of air is a bit disappointing. Minor EQ adjustments could not really fix this, so I just let it be. Those who are using to hearing HD800 plankton and ambient cues will definitely notice this.
     
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    Last edited: Feb 25, 2021
  17. rhythmdevils

    rhythmdevils Best SBAF member of all time

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    May God have mercy on my soul. :eek:
     
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  18. crenca

    crenca Friend

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    Well, I have a low Q -5db @ 3500k in Roon for FDX1 (with most damped filter nozzle), so I am not sure I will be turning the ZEN down to 11 all Spinal Tap style, but surely 8 or 9 at least. I do have the FDX1 bass/subass with about a +3 so I wonder if I will leave the Zen bass alone. Looking forward to hearing these, though I like the FDX1 I am anticipating a bit of a bit of a "potential, not fulfilled" story. This hobby is all about exploded expectations so we will see...
     
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  19. Alondite

    Alondite Acquaintance

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    The alternate distortion measurements seem to more closely reflect what you're hearing, which makes sense given that it's where the distortion actually manifests, i.e. where we actually hear it. Are you noticing a trend with that or is it more of a case-by-case basis?
     
  20. dan3952

    dan3952 Rando

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    If the drivers in the Zen sounds like the Al/Mg drivers in the Focal Clear headphones I used to have, then I think the fatigue experienced is mainly due to the characteristics of a certain type of metal driver: that is to say, a lot of detail is present, but presented in an intense, hyped up way that, especially when listening to percussion, isn't warm or lush. People call Focal headphones, "technical"; that is to say, they have an astonishing level of resolution, but not always presented in an enjoyable way. I hadn't found it objectionable when listening to certain types of music.

    I don't think the third order distortion rise visible on the graphs presented is audible, for anybody. My records show that distortion only starts to be audible at the frequency shown, once it gets to 32 db below the music; that is to say, the distortion is masked to that degree. My reference is a paper called, "An Axiom Experimental Study" by Alan Lofft, Ian Colquhoun and Tom Cumberland.
     

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