Short answer: the Kiwi Ears Forteza. Both are rated 3.8/5 for sound quality (#575 and #562 of 1291 in-ear headphones), and the Kiwi Ears Forteza costs $59 against $65.99 for the KZ ZAX, so with nothing between them on sound quality, price settles it.
Why pick the Kiwi Ears Forteza: The median of 16 hobbyist measurements gives it a solid Harman preference score of 71 with a 1.97 dB spread. Watch for: A 10.7 dB peak near 8.2 kHz can make cymbals and sibilance sound sharp.
Why pick the KZ ZAX: Across hobbyist measurements on squig.link sub-bass sits within 0.2 dB of target down to 20 Hz, and a 3.2 dB bass lift adds warmth and punch for pop and electronic music. The tradeoff: A 9 dB peak near 11.2 kHz lifts the top octave about 6 dB above target, which can make cymbals and sibilants sound sizzly on bright recordings, and a 3.8 dB dip near 3.4 kHz slightly recesses vocals.
Buy the Kiwi Ears Forteza. Both are rated the same for sound quality, and it costs $6.99 less than the KZ ZAX.
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The median of 16 hobbyist measurements gives it a solid Harman preference score of 71 with a 1.97 dB spread.
Amazon $59.00 eBay
Across hobbyist measurements on squig.link sub-bass sits within 0.2 dB of target down to 20 Hz, and a 3.2 dB bass lift adds warmth and punch for pop and electronic music.
Amazon $65.99 eBayPrices on this page were last checked October 16, 2026 at 5:46 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
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Specifications Side By Side
| Kiwi Ears Forteza | KZ ZAX | |
|---|---|---|
| Price | $59.00 | $65.99 |
| Ranked | #575 of 1291 in In-Ear Headphones | #562 of 1291 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Connection | Wired | Wired |
| Driver Type | Hybrid | Hybrid (1 dynamic + 7 balanced armature) |
| Drivers | 2 x 10mm dynamic + 1 x balanced armature | 1 x dynamic + 7 x balanced armature |
| Impedance | 32 ohms | 24 ohms |
| Sensitivity | 103 dB/mW | 113 dB |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) | 10Hz - 40kHz (Manufacturer specified) |
| Harman Preference Score | 71 (median of 16 squig.link measurements, calibrated to AutoEQ) | 71 (measured by crinacle, via AutoEQ) |
| Deviation From Target | 1.97 dB standard deviation | 2.29 dB standard deviation |
| Tonal Tilt | -0.17 (negative is warmer, positive brighter) | -0.43 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+3.7 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (-0.7 dB at 30 Hz) |
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 Kiwi Ears Forteza from achoreviews, aden, aftersound, audioamigo, bloomaudio, hbb, ianfann, jaytiss, joshtbvo, kr0mka, kuping-sensi, musicafe, pw, rg, soundcheck39 and vortexreviews; the KZ ZAX from achoreviews, melatonin, pw and vortexreviews, all via squig.link.
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