INTRODUCTION AND DISCLAIMER:
The KZ ZAX is a hybrid in-ear monitor (IEM) with a 10mm PEK spring diaphragm dynamic driver (DD) and seven balanced armatures (BAs) on each side. KZ is one of the biggest names in ChiFi, and I thought highly of the ZSX “Terminator,” KZ’s last major wired hybrid IEM release. However, following the release of the ZSX, KZ’s previously frenetic release schedule slowed to trickle, and what new products they did announce fell mostly into the total wireless stereo (TWS) category. The release of the ZAX comes as a surprise and relief to those that feared KZ had, in fact, “terminated” their hybrid endeavors.
The KZ ZAX was provided to me for review by Linsoul Audio and retails for $60. This is appreciably more expensive than the ZSX, which retailed at the lower end of the $40–50 price bracket at release. Other KZ and KZ-affiliated IEMs I’ve heard include the KZ ZSX, CCA C10, Tripowin TP10, KZ AS10, KZ ATE, and KZ ED9.
PACKAGING AND ACCESSORIES:
The KZ ZAX comes in a small rectangular black box with a lid that opens to the left. The box is unmarked apart from the KZ logo printed on the front of the lid. Stickers on the left face of the box indicate the selected mic and color options, as well as KZ’s contact information in Chinese and English. The ZSX comes with a detachable .75mm 2-pin cable, three pairs of KZ Starline-type black silicone eartips (S, M, L), a user manual, a QC pass chit, and a warranty card. The ZSX does not include a carry bag or case.
BUILD QUALITY / DESIGN:
The KZ ZAX follows the now-familiar design archetype typical of the last couple of years of KZ-affiliated IEMs, with a metal faceplate and a semi-transparent inner acrylic body. The metal faceplates are vented, though as I will discuss later the function these vents serve is mysterious to me. The housing has a teardrop-shaped cross-section. The ZAX’s inner acrylic body is less overtly ergonomic than the ZSX, omitting the latter’s bulbous protrusion on the top half of the housing. The nozzle is swept forward from the bottom corner. “ZAX — 16 Units Hybrid Technology” is written on the top face of the acrylic body just below the faceplate seam. The nozzles are metal, with a small lip for securing eartips. Each earpiece has two small circular vents on the inner face of the housing. I did not notice any driver flex with the TRN memory foam eartips I used for this review.
The four-strand 4N oxygen-free copper silver-plated cable is a huge improvement over the KZ norm. It has little-to-no microphonics and is much less tangle-prone than other KZ stock cables. The cable has a clear rubber jack and Y-split hardware and clear plastic housings for the 2-pin connections. There strain-relief above the 3.5mm jack and at all junctures of the Y-split. The 3.5mm jack is L-shaped. The 2-pin connectors use the KZ “type-C” recessed connector and have indented markings to indicate left and right. These markings are difficult to distinguish in dim lighting. The cable has pre-formed ear-guides without memory wire. The KZ logo is embossed on the 3.5mm jack housing. There is no chin-adjustment choker, at least on the mic’d cable that I received.
COMFORT / FIT / ISOLATION:
The KZ ZAX is intended to be worn cable-up only. The earpieces have a moderate insertion depth and were comfortable for me. The housings protrude moderately above the surface of the ear. Secureness of fit is average and the earpieces need periodic readjustment. I suspect this is due to the nozzle angle not being ideal for my ears. Despite the vents on the faceplates, there is negligible sound leakage and isolation is above average.
My measurements were conducted with a Dayton iMM-6 microphone using a vinyl tubing coupler and a calibrated USB sound interface. The headphones are driven using my Element, which has an output impedance of no more than 1 ohm. The measurements use a compensation file derived from relating my raw measurements to published measurements from Crinacle and Antdroid. The indicated SPL readings are not accurate. The measurements are presented with 1/24th smoothing. There is a resonant peak at 8k. Measurements above 10k are not reliable.
I do want to take a moment to congratulate KZ for their consistently excellent channel matching at all price points. I have a review forthcoming of several IEMs with retail prices orders of magnitude above the KZ ZAX with horrifically bad channel matching. This is completely unacceptable and unfortunately quite common.
A Note on the Vents:
The faceplate vents, while real and not cosmetic, do not seem to serve a sonic purpose. There is a tiny amount of sound leakage from the vents, but covering the vents with one’s fingers or tape does not appreciably change the ZAX’s frequency response. Covering the vents may have some effect on soundstage, but it is difficult to say for certain. Although putting pressure on the faceplates while listening has a definite effect on the sound produced by the ZAX, this does not vary based on the degree to which the vents are covered, rather, it depends on how hard and far one pushes the earpieces into the ear canal. This may in fact result from the two circular vents on the inner face on the housing being covered with deeper insertion.
The KZ ZAX has a more balanced sound signature than what I expect from KZ IEMs. The ZAX is U-shaped rather than V-shaped. It has a more aggressive bass response than can be defended as “neutral,” but the bass is less elevated than most other IEMs I have reviewed. In addition, the upper midrange and lower treble are restrained by Chi-Fi standards.
The bass tuning exhibits an elevated sub-bass shelf falls in a linear fashion before receding into the lower midrange. Sub-bass extension is excellent but I would have preferred the bass shelf recede slightly earlier, as there is a fair amount of mid-bass bleed that creates congestion in the midrange. The bass response is meaty and textured, with fast attack, but prioritizes note weight over agility. Notes have organic decay but the DD strains to keep up with faster musical passages. The ZAX lacks the sense of effortless speed that characterizes the bass performance of higher-end DDs. The overall bass resolution is very good, however.
The midrange has a cool tonality. There is enough presence to lend vibrancy to female vocals and bite to electric guitars, but not so much that either of these things sound harsh or overwrought. Though male vocal intelligibility is very good, there is a nagging sense that male vocals and drums lack body. The intelligibility of female vocals is equally good, and there are no issues with sibilance. Female vocals have slightly more color than male vocals. Male and female vocals roughly level with each other. There is a hint of BA plasticity but not as much as one would expect given the price point.
The treble response is smooth and extended, with ample air. Detail retrieval is good but avoiding harshness is more of a priority. The lower treble is restrained and fans of older or cheaper KZ offerings may find themselves wishing for a more sparkly presentation. Transient delivery is realistic and avoids being overly splashy. Soundstage width and depth are in line with my expectations for a hybrid IEM at this price point. Imaging is very good and instrument separation is mostly exceptional, held back only by some lower midrange congestion on bass-heavy tracks. The ZAX is easy to drive with a variety of source devices.
KZ ZAX vs KZ ZSX
The ZAX is recognizable as an evolution of its predecessor with some marked improvements. The wooly bass of the ZSX is more distinct and resolving on the ZAX. The ZAX’s upper midrange is more restrained and even-sounding, avoiding the sibilance that sometimes accompanied female vocals on the ZSX. The ZAX’s treble presentation is also slightly smoother.
KZ ZAX vs TinHiFi T2 Plus
These two IEMs are extremely competitive and choosing between them requires distinct trade-offs. The KZ ZAX has a slightly smoother yet more detailed treble presentation than the TinHiFi T2 Plus. The T2 Plus has better overall bass articulation and less congestion in the lower midrange. Neither IEM is “bad” with respect to their bass or treble presentation but each has a different strength.
CLOSING WORDS AND PRODUCT LINK:
The KZ ZAX meaningfully improves over the ZSX and is competitive with the other heavy hitter at the $60 price point. If you are beginning your IEM journey, there’s never been a better time to start (shipping delays excepted).
The KZ ZAX can be purchased at the link below: