Overview

The KZ ZST X is an upgraded version of the popular KZ ZST featuring a hybrid driver configuration with 1 balanced armature and 1 dynamic driver. Launched as part of KZ’s budget-oriented lineup, it represents the company’s approach to combining dynamic and balanced armature drivers for enhanced sound reproduction. The ZST X features a 10mm dual magnetic dynamic driver paired with a 30095 balanced armature unit positioned to minimize high frequency loss, along with a detachable 0.75mm 2-pin cable system.

Scientific Validity

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Evaluation based on available manufacturer specifications with conservative adjustment. The KZ ZST X specifications include 20Hz-40kHz frequency response, 12Ω impedance, and 107dB/mW sensitivity [1]. While credible third-party measurements for critical audio quality metrics including THD, SNR, Dynamic Range, IMD, or Crosstalk are unavailable for the ZST X specifically, manufacturer specifications provide baseline performance indicators. The claimed frequency response range of 20Hz-40kHz exceeds standard transparent level criteria (20Hz-20kHz ±0.5dB), though deviation tolerances are not specified. Given the lack of third-party verification, a conservative evaluation applies 0.5 as per policy for non-third-party measurements.

Technology Level

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The KZ ZST X employs KZ’s proprietary hybrid driver technology developed since 2014, featuring a 10mm dual magnetic dynamic driver paired with a 30095 balanced armature unit positioned at the front end to reduce high frequency loss [1]. KZ operates their own acoustic laboratory for product development and testing, with extensive iteration processes including over 10,000 tests for ear canal fitting optimization. The implementation includes Hi-Fi silver plating wire and High-Si Kevlar fiber core to reduce signal transmission loss and distortion. However, the analog-only approach lacks integration with modern digital signal processing or advanced software technologies. While representing accumulated know-how in hybrid configurations, the technology offers limited competitive differentiation that competitors could not readily replicate.

Cost-Performance

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The ZST X at 20 USD faces direct competition from the 7Hz Salnotes Zero at 20 USD, which offers equivalent functionality with superior build quality including metal composite diaphragm and documented frequency response measurements. However, since comprehensive third-party measurement data comparing critical audio quality metrics (THD, SNR, Dynamic Range, IMD, Crosstalk) between these products is unavailable, direct performance comparison cannot be definitively established. Based on available manufacturer specifications and functional equivalence (detachable cable, similar sensitivity, compatible impedance), both products offer comparable user-facing functionality at identical pricing. With no cheaper equivalent option available in the current market, CP = 20 USD ÷ 20 USD = 1.0.

Reliability & Support

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KZ provides a standard 1-year warranty covering manufacturing defects and workmanship issues under normal use [2]. However, individual customer reports indicate reliability concerns including documented cases of early failures, with one reported instance of single-side failure after approximately one month of use [4]. Some individual customers have reported difficulties with warranty support response, with one customer describing their experience as problematic when attempting to contact KZ support via email [4]. The primarily dealer-based support infrastructure relies on authorized distributors rather than direct global manufacturer support, potentially resulting in variable service quality across different regions and resellers.

Rationality of Design Philosophy

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KZ’s design philosophy emphasizes “sound quality above all else” with the mission to “provide high-quality audio equipment to fellow music lovers” and claims to deliver “studio-grade original sound at one-tenth of the price” [5]. Founded by Keith Yue (audio technology engineer) and Zen Li (Western-trained classical musician), the company established proprietary hybrid driver technology as a core innovation since 2014 [5]. While KZ operates their own acoustic laboratory and conducts extensive testing (over 10,000 iterations for optimal ear canal fitting), the approach lacks scientific measurement focus with public verification of performance claims. The conservative analog-only methodology shows limited integration of modern technologies like DSP, software processing, or advanced digital features that could provide superior measured performance at equivalent price points.

Advice

The KZ ZST X represents a conventional entry in the budget hybrid IEM market with competitive pricing among equivalent hybrid configurations. At 20 USD, the ZST X matches the pricing of established competitors like the 7Hz Salnotes Zero, making cost-performance comparable between these options. The lack of verified third-party measurements makes objective performance evaluation impossible, creating uncertainty about actual audio quality delivery. Potential buyers should consider that reliability concerns and inconsistent warranty support may impact long-term ownership experience. For those specifically seeking hybrid driver configuration, the ZST X provides adequate value at current pricing, though buyers should ensure comparison with current market alternatives that provide documented measurement data and stronger support infrastructure.

References

[1] KZ Audio, “KZ ZST X

Fast worldwide delivery!”, https://kz-audio.com/kz-zst-x.html, accessed 2025-09-23

[2] KZ Headphones, “Returns and warranty”, https://www.kzheadphones.com/pages/returns-and-warranty, accessed 2025-09-23

[3] SoundGuys, “7Hz Salnotes Zero - Best budget IEMs in 2025”, https://www.soundguys.com/best-budget-iems-132439/, accessed 2025-09-23

[4] TechEnclave, “Review - KZ Warranty is Fraud”, https://techenclave.com/threads/kz-warranty-is-fraud.217712/, accessed 2025-09-23

[5] KZ Audio, “KZ Earphones

Fast worldwide delivery!”, https://kz-audio.com/, accessed 2025-09-23

(2025.9.23)