KZ Castor Review

KZ Castor Review

KZ Castor Review – Cheapest Dual-Driver Harman-Tuned IEM

The KZ Castor comes in two versions – Harman Target and Harman Target with Improved Bass. Both models offer a new standard in sound quality by closely adhering to the acclaimed Harman FR curve.

KZ Castor Review

The KZ Castor is engineered with an innovative stacked dual-dynamic driver structure. One 10mm driver is solely focused on the 20-200Hz range to deliver powerful bass, while the other 8mm driver takes care of mid and high frequencies.

KZ Castor Review

The Harman Target with Improved Bass Version pushes the envelope with a low-frequency drop of over 10dB in the 40Hz-300Hz range.

KZ Castor Review

KZ Castor comes with professional-grade filters allowing for two-stage adjustments for both low and high frequencies. Users can personalize their audio experience with up to 16 different profiles to match their music preferences.

KZ Castor Review

The earphones boast a top and bottom-stacked cavity design that strikes a perfect balance between sound quality and wearing comfort.

KZ Castor Review

With an integrated injection molding process that is more than 10 times more precise than traditional 3D printing, KZ Castor’s internal support structure boasts a staggering precision of around 0.01mm.

What’s in the box


  • Frequency Range: 20-40000Hz
  • Impedance: Harman Target Version: 31-350Ω, Harman Target with Improved Bass Version: 16-200Ω
  • Sensitivity: Harman Target Version: 105±3dB, Harman Target with Improved Bass Version: 103±3dB
  • Plug Type: 3.5mm
  • Pin Type: 0.75mm
  • Cable: Flat transparent black cable
  • Cable Length: 120±5cm
  • Price: $14 Harman version, $17 Improved Bass version.

I would like to thank KZ Audio for providing me with the review sample of  KZ Castor.


KZ Castor FR Graph

I reviewed the Harman Target version of the Castor and as usual, I put all the switches down and tested in its standard tuning. In All Down mode, the Castor sounds very close to the CCA Duo that I reviewed a while ago which I liked a lot.

KZ Castor Review

And for just half the price the KZ Castor Harman edition sounds as good as the CCA Duo even as the Truthear RED when you play with the switches.

KZ Castor vs Truthear RED


If there’s any reason to go for the KZ Castor, it’s the bass. There’s a ton of body to the tone, and it dives deeper than you think. Its surface has a good consistency to it, providing smooth grooves of texture. You even get a hefty helping of sub-bass vibration. It feels like the bass is alive, and it can crawl down to your core. Overall it establishes a great foundation for the sound signature, and will certainly engage bass lovers.

KZ Castor Review

The sub-bass is slightly more prominent than the rest of the bass range, however, the bass feels abundant altogether. The textured, powerful bass contributes to the fun factor of the IEM. It’s tuned in a way (Harman 2019 curve v2) to prevent the bass from bleeding into the lower midsection. The detail level is also good. The Castor performs well in this regard, the bass is controlled, very powerful, and quite exciting to listen to.


The overall signature feels quite spacious, as well as the stage and the space between the instruments. The midrange has a linear tonality. The response is fairly clean. Nothing ever feels too centered, as the KZ Castor organized the sound elements well. There isn’t as much drive to its tone as the bass, but nothing is too recessed either. The instruments are clear enough, and they keep the sound as articulate as it can be. Vocal performances cut through very well, never feeling like they’re too far in the background.

KZ Castor Review

The resolution and detail retrieval are really good here, you can hear and track micro-details and individual instruments on the stage, easily. The slightly recessed midrange does not stick out at all, it feels quite alright, following the rest of the spectrum effortlessly. The Castor has an elevated upper midrange with a crisper tone.


The treble range of the IEM follows the bass line, they are a little more pronounced compared to the lower midrange. The second dynamic driver does a great job of reproducing detailed, articulate, and clean treble. The resolution and detail level are certainly impressive for this price and the extension is quite satisfactory. The dispersion of extended highs of the Zero helps stereo imaging and enhances the perception of stage height and width.

KZ Castor Review


The soundstage is one of the strong suits of the Castor. The instruments have accurate positioning with ample space between them and you can easily track individual instruments on the stage. The KZ Castor also handles congestion quite well thanks to its well-tuned signature and technical prowess.


The KZ Castor does more than I thought in terms of sound quality. It’s hard not to recommend it for just $14. KZ may have broken a record with Castor for the cheapest dual-driver Harman-tuned IEM.