Short answer: the KZ ZST on measured sound quality, the KZ ZST X on price. The KZ ZST ranks #632 of 1369 in-ear headphones, rated 3.7/5, at $22.99. The KZ ZST X ranks #849, rated 3.5/5, at $6.99, $16 cheaper.
What the KZ ZST does well: In oratory1990’s measurement the preference score is 70, with bass about 2.3 dB above target from 60 to 200 Hz for extra warmth and punch, and sub-bass tracking the target within 0.1 dB. Watch for: A 9.4 dB dip near 4.4 kHz and 3.7 dB lower presence from 3 to 6 kHz pull back vocal clarity and the attack of snares and guitars.
The case for the KZ ZST X: A broadly balanced tuning with a preference score of 67 against the Harman target. The catch: An uneven response, 2.5 dB standard deviation from target.
Buy the KZ ZST when sound quality outweighs the price for you, and the KZ ZST X when the price outweighs sound quality instead.
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In oratory1990’s measurement the preference score is 70, with bass about 2.3 dB above target from 60 to 200 Hz for extra warmth and punch, and sub-bass tracking the target within 0.1 dB.
Amazon $22.99 eBay
A broadly balanced tuning with a preference score of 67 against the Harman target.
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Specifications Side By Side
| KZ ZST | KZ ZST X | |
|---|---|---|
| Price | $22.99 | 6.99 |
| Ranked | #632 of 1369 in In-Ear Headphones | #849 of 1369 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Harman Preference Score | 70 (measured by oratory1990, via AutoEQ) | 67 (median of 8 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 2.31 dB standard deviation | 2.46 dB standard deviation |
| Tonal Tilt | -0.47 (negative is warmer, positive brighter) | -0.45 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+0.1 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (+0.4 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Hybrid (1 dynamic + 1 balanced armature) | Hybrid |
| Drivers | 1 x 10mm dynamic + 1 x balanced armature | 1 dynamic driver + 1 balanced armature (10mm dynamic + 30095 balanced armature) |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) | 20Hz - 40kHz |
| Back | Closed | Closed |
| Impedance | - | 12 ohms |
| Sensitivity | - | 107 dB/mW |
| Weight | - | 0 lbs (22 g) |
Frequency Response Compared
Both headphones’ measurements overlaid on the Harman target. Above the target sounds louder in that range, below it quieter. Each curve is the median of several independent measurements, shifted so its 500 Hz to 2 kHz average sits at 0 dB, so only the tuning is compared.
Measurement data: the KZ ZST from audioamigo, bassyalexander, hbb, iemocean, isaiahse, melatonin and sl0the; the KZ ZST X from achoreviews, aftersound, bukanaudiophile, eplv, hbb, melatonin, pw and vortexreviews, all via squig.link.
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