Short answer: the KZ ZST X. It ranks #849 of 1369 in-ear headphones by sound quality, rated 3.5/5, at $6.99; the Tanchjim Ola II ranks #900, rated 3.4/5, at $6.99. With prices this close, go by the sound-quality ranking rather than the cost.
Why pick the KZ ZST X: A broadly balanced tuning with a preference score of 67 against the Harman target. Watch for: An uneven response, 2.5 dB standard deviation from target.
Why pick the Tanchjim Ola II: A broadly balanced tuning with a preference score of 66 against the Harman target. The tradeoff: An uneven response, 2.6 dB standard deviation from target.
Buy the KZ ZST X. It is rated higher for sound quality than the Tanchjim Ola II at the same price, which makes it the one to get unless you need something the other one does better.
Still deciding? The full Headphones rankings cover every ranked option.
A broadly balanced tuning with a preference score of 67 against the Harman target.
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A broadly balanced tuning with a preference score of 66 against the Harman target.
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Specifications Side By Side
| KZ ZST X | Tanchjim Ola II | |
|---|---|---|
| Price | 6.99 | 6.99 |
| Ranked | #849 of 1369 in In-Ear Headphones | #900 of 1369 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 67 (median of 8 squig.link measurements, calibrated to AutoEQ) | 66 (median of 6 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 2.46 dB standard deviation | 2.58 dB standard deviation |
| Tonal Tilt | -0.45 (negative is warmer, positive brighter) | -0.35 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+0.4 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (-2.8 dB at 30 Hz) |
| Driver Type | Hybrid | Hybrid |
| Drivers | 1 dynamic driver + 1 balanced armature (10mm dynamic + 30095 balanced armature) | 1 dynamic driver + 1 balanced armature (10mm DMT5 dynamic + PURE Hi balanced armature) |
| Impedance | 12 ohms | 30 ohms |
| Sensitivity | 107 dB/mW | 121 dB/Vrms |
| Frequency Response | 20Hz - 40kHz | 8Hz - 48kHz |
| Weight | 0 lbs (22 g) | 0 lbs (5 g) |
| Connection | Wired | Wired |
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 X from achoreviews, aftersound, bukanaudiophile, eplv, hbb, melatonin, pw and vortexreviews; the Tanchjim Ola II from aftersound, atechreviews, audioamigo, csi-zone, samreviews and soundignity, all via squig.link.
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