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KZ ZSX IEM Review

Rate this IEM:

  • 1. Poor (headless panther)

    Votes: 26 17.1%
  • 2. Not terrible (postman panther)

    Votes: 59 38.8%
  • 3. Fine (happy panther)

    Votes: 59 38.8%
  • 4. Great (golfing panther)

    Votes: 8 5.3%

  • Total voters
    152

amirm

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This is a review, measurements, listening tests and equalization for KZ ZSX IEM. It is on kind loan from a member and costs US $60.
KZ ZSX IEM frequency response review.jpg

Not much to say about the look of the unit. The owner sent me one set of tips which I used for measurements. They were kind of worn out but still worked out well. For listening tests, I grabbed one I had on hand which you see in the picture above. They did not provide a complete seal for long unless I kept pushing them in every couple of minutes. Expectedly, bass would response would drop some when that happened.

The unit has 5 BA and 1 DD driver. I assume the number 12 comes from two times six.

KZ ZSX IEM Measurements
As usual, we start with frequency response measurements of the IEM and comparison to our target:
KZ ZSX IEM frequency response measurement.png

I was relieved to see proper level of bass and generally good compliance with our target. For the purposes of EQ, we want to see the deviation from our target:
KZ ZSX IEM frequency relative response measurement.png


Distortion test revealed a clear problem with the design:
KZ ZSX IEM frequency relative THD distortion measurement.png

KZ ZSX IEM frequency THD distortion measurement.png

It is a shame more people don't do distortion tests as it so clearly demonstrates problems like this.

Group delay is usually clean with IEMs and such is the case here:
KZ ZSX IEM Group Delay measurement.png


Impedance is flat and low:
KZ ZSX IEM Impedance measurement.png

Combined with good sensitivity, you should have no trouble driving these IEMs to loud levels:
Most sensitive IEM review.png


KZ ZSX IEM Listening Tests and Equalization
Out of box experience was non-offensive but not exciting either. I expected it to sound better than it did give the small variation from target. Turns out those differences matter when we perform AB test with EQ correction:
KZ ZSX IEM Group equalization.png


The yellow filter gave the IEM huge boost in spatial effects, rising to delightful levels! The sharp filter in teal was put in there for distortion reduction. Without it the sound was a bit grungy and muddy (in limited blind testing). I initially put in correction for shortfall in higher frequencies with Bands 5 and 6. Alas, that made the IEM too bright after a few seconds of listening especially since I could not maintain good seal/bass response. So I disabled them.

Once there, the experience with my reference tracks was incredible! I often forget how great these IEMs can sound. Detail, resolution, and spatial experience per above, was superb. I didn't want to stop listening. The only miss was lack of deep bass as I have stated which may have been remedied using a different tip.

Conclusions
I very much like that KZ has made an attempt to give us bass and general response that is close to our target. The distortion is unfortunately though. My correction took a way of a bit of tonality to reduce that. Audibility may not be there due to narrowness of it but still, I like to see that remedied. Sensitivity is quite good unlike some otherwise excellent IEMs I have tested.

Overall I am fine with out of box experience so going to recommend the KZ ZSX. Add some EQ to it and this IEM becomes reference quality, blowing away vast majority of home systems.

Manufacturers Specifications:​

Model: KZ ZSX
Weight: 31g
Wear: In-ear earphone
Sensitivity: 111dB
Impedance: 24Q
Frequency: 7-40000Hz
Line Length: 1.25±0.04m
Plug Type: 3.5mm gold plated
Pin Type: 0.75mm gold plated

------------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

Attachments

  • KZ ZSX Frequency Response.zip
    33.6 KB · Views: 51
Last edited by a moderator:

kemmler3D

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What a strange issue at 800hz. I wonder if maybe there is something mechanically wrong or broken with the unit ? Although if it showed up in both the L and R then it's clearly not that.
 
OP
amirm

amirm

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What a strange issue at 800hz. I wonder if maybe there is something mechanically wrong or broken with the unit ? Although if it showed up in both the L and R then it's clearly not that.
It is in both channels. Could be a resonance.
 

Matias

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Too bad KZ has a terrible reputation in the market...
 

kemmler3D

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Wow, shady. Paying influencers to promote your products is normal in all consumer categories. However, paying for reviews is not (as) normal or ethical. Conflating influencer marketing and paid-for reviews and then blaming influencers for taking commission is just dirty.

Even if nothing Crinacle says in that post is true, KZ's statement directly shows they're not really honest, because they're deliberately trying to muddy the waters around how marketing works!
 

ALaylowguy

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$60 makes this IEM kinda hard to swallow when you consider the blue Truthear Zero with better prices and more "toned down?" design. Don't want to be a spoiled child but with Crinacle's blessing, it's hard!
 
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half_dog

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It is in both channels. Could be a resonance.
This peak around 900 to 1000Hz was quite common around some IEMs with dynamic drivers - maybe an enclosure or driver size related? The few other reviewers who used to measure THD displayed this in some IEMs like Moondrop Aria, Sartfield, Salnotes Zero, Moondrop Chu (if I'm not mistaken) etc.
 

Attachments

  • Screenshot_20231110_000230_Chrome.png
    Screenshot_20231110_000230_Chrome.png
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Maiky76

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Here are some thoughts about the EQ.


Notes about the EQ design:


  • The average L/R is used to calculate the score.
  • The resolution is 12 points per octave interpolated from the raw data (provided by @amirm)
  • A Genetic Algorithm is used to optimize the EQ.
  • The EQ Score is designed to MAXIMIZE the Score WHILE fitting the Harman target curve (and other constrains) with a fixed complexity.
    This will avoid weird results if one only optimizes for the Score.
    It will probably flatten the Error regression doing so, the tonal balance should be therefore more neutral.
  • The EQs are starting point and may require tuning (certainly at LF and maybe at HF).
  • The range around and above 10kHz is usually not EQed unless smooth enough to do so.
  • I am using PEQ (PK) as from my experience the definition is more consistent across different DSP/platform implementations than shelves.
  • With some HP/amp combo, the boosts and preamp gain (loss of Dynamic range) need to be carefully considered to avoid issues with, amongst other things, too low a Max SPL or damaging your device. You have beed warned.
  • Not all units of the same product are made equal. The EQ is based on the measurements of a single unit. YMMV with regards to the very unit you are trying this EQ on.
  • I sometimes use variations of the Harman curve for some reasons. See rational here: https://www.audiosciencereview.com/...pro-review-headphone.28244/page-5#post-989169
  • https://www.audiosciencereview.com/...pro-review-headphone.28244/page-6#post-992119
  • NOTE: the score then calculated is not comparable to the scores derived from the default Harman target curve if not otherwise noted.
  • Occluding IE devices generally must have very good fitting/seal in the user's ear canal for best performance.
    please spend a few minutes to pick up the best ear tip... Be sure to perform this step otherwise the FR/Score/EQ presented here are just worthless.
  • 1. more bass = better seal
    2. More isolation from the outside world = better fit
    3. Comfort

Decent L/R match.
Since I did not perform any listening test I let the addition of the notch added by Amirm to the user discretion.

I have generated one EQ, the APO config file is attached.

Score no EQ: 65.5
Score Amirm: 66.0
Score with EQ: 96.6

Code:
KZ ZSX Frequency Response Harman Full EQ
November102023-130735

Preamp: -5.9 dB

Filter 1: ON PK Fc 32.24 Hz Gain -1.51 dB Q 0.33
Filter 2: ON PK Fc 175.83 Hz Gain -4.31 dB Q 0.72
Filter 3: ON PK Fc 626.05 Hz Gain 1.83 dB Q 1.35
Filter 4: ON PK Fc 1861.24 Hz Gain -5.06 dB Q 1.33
Filter 5: ON PK Fc 3169.33 Hz Gain 4.36 dB Q 2.89
Filter 6: ON PK Fc 4299.54 Hz Gain -2.84 dB Q 6.98
Filter 7: ON PK Fc 6066.35 Hz Gain 3.24 dB Q 3.80
Filter 8: ON PK Fc 8992.35 Hz Gain 6.19 dB Q 3.69
Filter 9: ON PK Fc 10946.30 Hz Gain -5.29 dB Q 6.98

KZ ZSX Frequency Response Harman Full EQ .png


The Scores are not comparable to the scores above as I have replaced the Harman target with the Knowles one.
Remember to be careful bout the boost at HF. You've been warned.

Score no EQ: 59.2
Score Amirm: 59.8
Score with EQ: 96.7

Code:
KZ ZSX Frequency Response Knowles Full EQ
November102023-131817

Preamp: -12.9 dB

Filter 1: ON PK Fc 35.99 Hz Gain -1.51 dB Q 0.22
Filter 2: ON PK Fc 179.39 Hz Gain -3.86 dB Q 0.72
Filter 3: ON PK Fc 628.05 Hz Gain 1.89 dB Q 1.35
Filter 4: ON PK Fc 1907.61 Hz Gain -5.17 dB Q 1.26
Filter 5: ON PK Fc 3166.28 Hz Gain 4.36 dB Q 2.38
Filter 6: ON PK Fc 4282.60 Hz Gain -3.10 dB Q 7.00
Filter 7: ON PK Fc 6054.04 Hz Gain 3.02 dB Q 4.64
Filter 8: ON PK Fc 9040.34 Hz Gain 6.27 dB Q 2.94
Filter 9: ON PK Fc 10886.80 Hz Gain -5.34 dB Q 7.00
Filter 10: ON PK Fc 14659.02 Hz Gain 12.72 dB Q 1.88

KZ ZSX Frequency Response Knowles Full EQ .png
 

Attachments

  • KZ ZSX Frequency Response Knowles Full EQ .txt
    589 bytes · Views: 41
  • KZ ZSX Frequency Response Harman Full EQ .txt
    534 bytes · Views: 35
Last edited:

GWolfman

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Would give it golfing panther if that resonance wasn’t there. But as it is, they feel “broken” to me.
 

nerdemoji

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I dont understand why this website is obsessed with the truthear zero and zero red. There are many better choices at lower prices these days.
 

renaudrenaud

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I dont understand why this website is obsessed with the truthear zero and zero red. There are many better choices at lower prices these days.
Thanks, we just need measurements.

Truthear Zero and Zero Red offer nice measurements and are pretty inexpensive.

And because most of us are laaaazzzzyyy, we just read reviews in this website and don't waste our precious time (semi nap enjoying listening to music) in other websites.
 

MacClintock

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If it must be KZ, I very much prefer the D-Fi, it's cheaper and has a nicer, metal shell. Also better frequency response. Hopefully it doesn't have this distortion peak.
 

IAtaman

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Thank you for the review Amir.

The larger issue with KZ performance in my opinion is that you never know what you are gonna get on the next manufacturing batch.

I dont understand why this website is obsessed with the truthear zero and zero red. There are many better choices at lower prices these days.
I am surprised it took 9 posts for someone to bring them up.
 
Last edited:

MrSoul4470

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Thanks, we just need measurements.

Truthear Zero and Zero Red offer nice measurements and are pretty inexpensive.

And because most of us are laaaazzzzyyy, we just read reviews in this website and don't waste our precious time (semi nap enjoying listening to music) in other websites.

WE just need meassurements? No YOU need them. I know both Truthear Zero and Zero Red and I actually prefer the KZ as it sounds more exciting and lifely to me. The Truthears sound really boring.
 
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