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KZ Castor Natural Review: Natural

On to the next Chi-fi legend on the list; we’ve got the KZ Castor. These earphones are currently hailed as one of the best-sounding IEMs out there by other enthusiasts. Modeling its frequency response range on the legendary Harmon curve, how good does it sound?

Before we start, we do need to point out two things. First off, there are two variants of the earphone: one is the natural variant, while the other one is a bass-enhanced version. We are testing the natural version here. The second thing is the KZ Castor has a unique filter to fine-tune high and low frequencies by flipping the four knobs at the back of the earphone. We are testing it with all knobs flipped up since we find that it sounds the best there.

KZ Castor Audio Quality


The KZ Castor has a unique natural-sounding profile. Its bass is accurate while gentle on the ear. It is very easy to listen to without fatigue. The highlight of the bass would be how well-layered and controlled it is.

The sub-bass is present, and I cannot emphasize enough on how gentle it sounds. Rather than a rumble that shakes the listener; it hums and radiates throughout the field. Listening to Ace Combat 7 Skies Unknown’s Dual Wielder, the bass is smooth and easy to hear, while each tone has its own lane to perform on.

However, when compared to the Moondrop Chu 2, the bass lacks striking force by default. It can be slickly remedied by tuning the.


I was expecting the KZ Castor’s mid-range to be less prominent based on how the Harmon curve is read; however, it seems to be nothing less than impressive.

The mid-range is presented with a significant amount of details and width. It extends out and feels natural, as if listening to gentle winds. It is amazing listening to vocal-heavy music regardless of gender. I was going through a classic cover of “Lion in Macros Fantier” by Studio aLF and Naomi. To put it simply, the vocals sounded organic and natural.


This is where KZ Castor’s natural really shines. Retaining gentleness and accuracy, it shines brightly, sounds crispy, and well-detailed. Lady’s vocals excel with this earphone, with higher frequencies raised yet showing no sign of sibilance nor fatigue. It shows the texture of vocals well, making it sound more natural and lively.

Listening to Rosa Walton’s “I Really Want to Stay At Your House” (Screw you Adam Smasher*) with its quick pacing and mixed instruments plays really well with her vocal in the KZ Castor. With the lack of sibilance issues, it makes the music significantly relaxing to give into.

Sound Stage

The sound stage for KZ Castor is impressive; it is wide with great positioning. In Ace Combat 7 Skies Unknown’s Two-Pronged Strategy, there is a chime that hovers around. With Castor, the movement of the chime is clear and lively, projecting a clear position of the chime.

KZ Castor Design & Comfortability:

The KZ Castor is significantly bigger than any other IEM in my collection that is in the sub-RM100 price range. It is at least twice the size of the Moondrop Chu 2, which also makes it bulkier to wear, noticeably protruding outward.

Unlike other earphones I’ve got so far, the KZ Castor comes with slow-rebound memory sponge eartips. This is a level higher than the common silicon eartips bundled with other IEMs, offering a different experience too. It provides great sound isolation and a great audio channel inward into the ear.

However, it would feel stuffy over time, as the form seems to continue pushing outward. It is less comfortable compared to silicone, so much so I exchanged the eartips with the Coreir Metal Core eartips to better conform.

KZ Castor Conclusion:

In summary, the KZ Castor earphones excel in the Chi-fi landscape, praised for exceptional audio quality. Featuring a unique natural profile, the accurate and gentle bass ensures a fatigue-free listening experience with impressive layering. Contrary to expectations, the mid-range surprises with detailed and expansive presentation, particularly in vocal genres.

The treble stands out as the Castor’s highlight, offering delicate yet accurate tones, delivering crispness and intricate detail without sibilance or listener fatigue. The expansive soundstage enhances the overall experience, providing clear positioning and dynamic audio reproduction. Despite its larger design and memory sponge eartips contributing to sound isolation, some users may find a slight sense of stuffiness over time.

In conclusion, the KZ Castor Natural earphones present a compelling option for audio enthusiasts seeking a balance of natural sound reproduction, detailed mid-range, and impressive treble clarity at an affordable price point. While considerations of size and comfort exist, the Castor lives up to its reputation as a noteworthy contender in the budget-friendly in-ear monitor market.

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