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KZ Castor Harman Target IEM Review

Rate this IEM:

  • 1. Poor (headless panther)

    Votes: 20 12.3%
  • 2. Not terrible (postman panther)

    Votes: 41 25.3%
  • 3. Fine (happy panther)

    Votes: 73 45.1%
  • 4. Great (golfing panther)

    Votes: 28 17.3%

  • Total voters
    162

amirm

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This is a review, listening tests, EQ and detailed measurements of the KZ Castor Silver IEMs with configuration Harman frequency response. It was kindly drop shipped to me by a member and costs US $22.
KZ Castor Tuning Adjustable Dynamic Dual Driver Earphone IEM Harman Review.jpg

The Castor is attractive while looking reserved and was comfortable to wear. It comes with three different sized silicon tips. I found them easy to take off and a pain to put back on. I used the default medium one for measurements and larger one for listening. The latter could be a bit larger to fully seal my ear canal.

The main differentiator here is a set of dip switches which vary the response of the headphone and stated compliance with Harman target:
KZ Castor Tuning Adjustable Dynamic Dual Driver Earphone IEM Harman Target 2 switches.png


Out of box all four switches were on. This caused a huge overshoot in treble, not reflected above. Through experimentation, I found that by setting switches 1 and 2 to on provided closes compliance to our target (see below).

KZ Castor Measurements
I was not sure which Harman target KZ has used. The shelving above in treble region made me think they assumed original version so I started the measurements with that:
KZ Castor Tuning Adjustable Dynamic Dual Driver Earphone IEM Original Harman Target.png


Then again it seems to comply a bit better with new target:
KZ Castor Tuning Adjustable Dynamic Dual Driver Earphone IEM Harman Target 2 frequency respons...png


I wish there was a switch to bring treble down but there isn't. You can only boost it. As is though, the differential is small:
KZ Castor Tuning Adjustable Dynamic Dual Driver Earphone IEM Harman Target 2 relative frequenc...png


Castor uses two different drivers. I am not sure of the transition frequency but there is a pronounced rise in distortion in lower treble:
KZ Castor Tuning Adjustable Dynamic Dual Driver Earphone IEM Harman Target 2 relative THD dist...png

KZ Castor Tuning Adjustable Dynamic Dual Driver Earphone IEM Harman Target 2 THD distortion me...png


Impedance is naturally not flat due to passive components to shape the response:
KZ Castor Tuning Adjustable Dynamic Dual Driver Earphone IEM Harman Target 2 impedance measure...png


Sensitivity is the lowest I have measured, ranking like a normal headphone:
most sensitive Harman IEM review 2024.png

So best to use a proper headphone amplifier to drive it.

Group delay is pretty clean as most IEMs are so I am not showing it.

KZ Castor Listening Tests and EQ
As noted, even the larger tips were not quite enough to fill my ear canal so I had to push them with my hands for best bass response. If you are so situated, you may want to get aftermarket tips. Listening out of box, the sound was good but I was curious what the effect of correction would be:

KZ Castor Tuning Adjustable Dynamic Dual Driver Earphone IEM Harman Target 2 equalization eq p...png

I paired two filters around 2 to 3 kHz to get a flat top response (eyeballed). Once there, I was surprised that I liked the response with EQ better. I say surprised because I tend to like a bit of extra energy in that region to give more spatial response. That was certainly better in stock response but the sound was a bit bright and grungy. Can't swear this is the case but it may be that I am hearing the harmonic distortion. Negative EQ there is helping lower distortion and with it, extra high frequency energy.

When I set the levels for measurements, I let the mid-frequency reference to be below 0 dB. I compensated for that using Band 3 and I liked the results. Got back a bit more warm and overall niceness for lack of a better word.

Difference is not night and day of course but I really liked the EQ response. Track after track sounded superb now, albeit, with slightly less impact in sub-bass which may be due to fitment.

Conclusions
I really, really like the idea of configurable frequency response. KZ comes close to nailing that but vagaries of measurement system differences and two "Harman" targets makes their job hard if not impossible. This is why I always talk about having one standard with one fixture and target. Otherwise while we can get close, we will still not be there. Still, what we have in Castor is major progress and you may just like the stock tuning. If not, that bit of EQ takes you to a more ideal place assuming your preference is similar to mine.

Distortion is a bit of a concern if my assumption of it adding some sharpness is right.

Overall, I am going to recommend the KZ Castor. It is a bargain at $16 with very good sound and excellent flexibility.
-----------
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 Castor Frequency Response.zip
    33.7 KB · Views: 66
Last edited:

Jasperous

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This seems weird and odd for an IEM. I’m no IEM fanatic but, the very low sensitivity means it can’t be run by your phone and if you have a headphone amp you aren’t going to buy this.
 

Maiky76

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Here are some thoughts about the EQ.
Please report your findings, positive or negative!

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, start your journey here or there.
    There is a presentation by S. Olive here.
    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 regard to the very unit you are trying this EQ on.
  • I sometimes use variations of the Harman curve for some reasons. See rational here and here
  • 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

Good L/R match.

I have generated three EQ, the APO config file are attached.

Score no EQ: 79.7%
Score Amirm: 86.3%
Score with EQ: 92.6%


Code:
Kz Castor Harman Full EQ
May072024-094337

Preamp: -0.0 dB

Filter 1: ON PK Fc 128.38 Hz Gain -2.30 dB Q 0.72
Filter 2: ON PK Fc 238.03 Hz Gain -1.14 dB Q 3.13
Filter 3: ON PK Fc 1340.24 Hz Gain -3.86 dB Q 1.81
Filter 4: ON PK Fc 3084.88 Hz Gain -3.74 dB Q 0.86
Filter 5: ON PK Fc 12689.30 Hz Gain -6.33 dB Q 3.75

Kz Castor Harman Full EQ .png



Edit: different tuning for the Harman curve
The first Biquad is optional, it looks good on paper but the fit is never perfect...

Score no EQ: 79.7%
Score Amirm: 86.3%
Score with EQ: 92.6%
Score with Harman 2: 95.6%

Code:
Kz Castor Harman Full 2 EQ
May072024-111133

Preamp: 0.00 dB

Filter 1: ON PK Fc 17.5 Hz Gain -2.10 dB Q 0.65
Filter 2: ON PK Fc 166.1 Hz Gain -2.47 dB Q 0.89
Filter 3: ON PK Fc 1368.5 Hz Gain -4.14 dB Q 1.62
Filter 4: ON PK Fc 3228.1 Hz Gain -3.74 dB Q 0.93
Filter 5: ON PK Fc 12721.5 Hz Gain -6.08 dB Q 3.31

Kz Castor Harman 2 Full EQ .png

Hereafter is the Knowles target is used. The scores are NOT comparable
Kz Castor Knowles Full EQ .png
 

Attachments

  • Kz Castor Harman Full EQ .txt
    315 bytes · Views: 37
  • Kz Castor Knowles Full EQ .txt
    312 bytes · Views: 35
  • Kz Castor Harman 2 Full EQ .txt
    316 bytes · Views: 43
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DWPress

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Pretty amazing for under $20. Wish I could stand to use IEMs.
 

markanini

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I own this IEM. Strong first impressions, expecially for the price, but beyond that I haven't used them much. The issue is with the sound being too V-shaped for my taste and there's some harshness up top. The distortion graph gives some clues as to why.

My pet theory about the KZ brand is that it's targeting a segment of consumers that pay attention to specs sheets. That's a reasonable assumption to make about wired IEMs. But the competition is tight in the budget segment and KZ is not putting in the final bit of effort on the acoustic tuning. KZs latest strategy is attracting consumers that pay attention to graphs and target curves. If you followed the brand over the years and a tried few of their IEMs you might agree.

Thanks Amir for the review!
 
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SoundsGood2Me

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Thanks Amirm, you're the only (reliable) un-biased reviewer there is! I hope you have someone in the wings to take your place, but I fear it's like my job installing antennas on Towers: no one wants to take over, it's actual work and you have to be self motivated.

But thanks for all the recommends, Rockin' my Benchmark system till it makes me deaf!
 

shuppatsu

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With all the competition in the low-end IEM market, I don't see any point in these, particularly given that they are so insensitive.

Also, KZ is famous for unethical business practices. From selling hybrid designs where the additional drivers were muted, to allegedly attempting to pay for positive reviews, to changing the performance on the PR2 after the initial batch without telling anybody... I'm a cheapskate and will jump at a bargain, but there are bargains galore in this space so why bother?

While we're here, does anybody have any opinions on whether multiple driver IEMs make sense any more, other than marketing? My impression is that they were favored in the early days because single dynamic drivers struggled to accurately reproduce the whole spectrum, but now there are single-driver designs with essentially zero distortion anywhere. Do the additional drivers help with IMD, or what's their deal?
 

lin4265

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Pretty amazing for under $20. Wish I could stand to use IEMs.
I wish the opposite. It's so easy for me to pop an ear piece in and go for a jog or chores around the house. Immerse myself with sound.
People around me goes away when I turn on the speakers. If noise level around me isn't too quiet or if I move, the sound is worse than ideal.
 

MacClintock

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It´s cheap and close to Harman, but has higher distortion than most other cheap IEMs measured here, hard to drive and is even brighter than the already bright Harman2019IEv2 target, so for me it loses on all fronts against the 7Hz Salnotes Zero 2.
 
Last edited:

peniku8

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Sensitivity is the lowest I have measured, ranking like a normal headphone:
View attachment 368047
So best to use a proper headphone amplifier to drive it.
Don't even the wimpiest of dongles reach like 2V on the output side nowadays?
That would be 120dB with these IEMs if my calculations are correct?
 

USER

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If it helps, I have the CCA Trios (one of the many, many, many iterations of these IEMs) and the similar FR response sounds a bit too bright to me as well. I have smaller ears and find that I need that area at or a bit below Harman 2019v2 or else I really don't like it. I've never thought it was due to distortion, however, which I did know was problematic in that area.

kz-castor-02-2-p-800.png
blob.jpg

graph (41).png
CCA Trio Distortion.jpg


I found from comparing numerous measurements that one of the biggest differences between GRAS 45CA-10 and the standard clone "711" used in many reviews is in that area. (I imagine this is due to the pinna.) Your measurements helped me identify my sensitivity to that area. I found that Moondrop Spring Tips (known to bring down highs a little) has a much larger effect on the Trios than on other IEMs. I highly recommend them as an alternative to EQ. I'd bet they would have a similar effect on the Castors.
graph (42).png
graph (43).png

My conversion seems to "work" quite well (for an amateur) against your measurements as well as Sean Olive's 45CA-10 results, so I am becoming more confident in it. (The overall consistency of modern manufacturing astounds me.)
graph (65).png


One funny thing is that I always considered the Trios as having a slightly wider soundstage than usual for IEMs, but I was always well aware that it was likely due to visual bias from seeing those vents. Interesting to see you have a different opinion as it helps to ground mine. (Assuming that circle on the body is a large vent.)

Finally, thank you for that impedance graph as the Trios were driving me a bit crazy with boomy bass when connected to my laptop. It took me a week to realize what was happening as the sound didn't match up to my measurements with an apple dongle. Too bad you have to be careful with sources with these IEMs.

Edit: This is the Trios vs these Castors. The Castors are more V-shaped and the Trios (basically updated Castors) more "Harman" (as they are described to be). To me it makes perfect sense that Amir would find this bright having heard the Trios.

graph (45).png


If I can add one thing to think about it is that because IEMs have gotten so well-tuned during the last year or so I think we can be more strict with what we call "Harman-tuned." We are starting to see more and more IEMs hitting target curves more closely than ever before (at least with respect to whatever measurement systems companies are using and the resonance people use to align insertion depth for their measurements), that I would call this a new era. These things are so far ahead of headphones in this regard. While I would last year, this year I would not say that the Castors meet Harman and I think the graph above illustrates why.
 
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virtua

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These are my favourite IEMs and sit on my desk daily. Tried Salnotes Zero and Zero:2, and they didn't do it for me like this one did. I rather like the QKZ x HBB too if I'm looking for more bass.

Would be interested to see a Truthear Nova review, as I'm quite curious about that set.
 

SuicideSquid

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Two years ago:

"Wow, I can't believe we can get this level of performance from a $50 IEM"

One year ago:

"Wow, I can't believe we can get this level of performance from a $25 IEM"

Today:

"Wow, I can't believe we can get this level of performance from a $16 IEM"

So next year, we can expect a $9 IEM that outperforms many ~$1,000 models?
 

virtua

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So next year, we can expect a $9 IEM that outperforms many ~$1,000 models?
I bought these from Aliexpress for the princely sum of $13 AUD shipped to my house - around 9 USD, so maybe you don't need to wait until next year? I'm sure there is plenty of worse sounding 1k IEMs than this one.
 
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