Short answer: the KZ ZAS, though neither ranks well in its class. It ranks #418 of 450 in-ear headphones by sound quality, rated 2.4/5, at $75.99; the Sennheiser IE 4 ranks #425, rated 2.3/5, and costs $89, so there is little reason to consider the other one. Both are rated below 3.0/5 among the 450 in-ear headphones; for better sound, the Intuaura Reference 2019 ranks #5 at $34.99.
What the KZ ZAS does well: Bass is lifted about 2 to 3 dB from 20 to 200 Hz, so bass-heavy genres have plenty of weight, and listeners with a bassy or warm taste are the best match. The catch: In hobbyist measurements on squig.link the presence range sits about 5.4 dB below target with a 7.5 dB dip near 3.4 kHz, which pushes vocals back and blurs detail.
Why pick the Sennheiser IE 4: Sub-bass and bass both sit more than 6 dB above target and extend fully to 20 Hz, a good match for listeners who want big, rumbling bass and a V shaped sound. The tradeoff: A huge 15.3 dB peak near 5.1 kHz and presence about 10 dB above target make vocals and snares sound shouty and fatiguing.
Buy the KZ ZAS. It is rated higher for sound quality than the Sennheiser IE 4 and costs less, which makes it the one to get unless you need something the other one does better.
Looking for alternatives? See the complete Headphones rankings.
Specifications Side By Side
| KZ ZAS | Sennheiser IE 4 | |
|---|---|---|
| Price | $75.99 | $89.00 |
| Ranked | #418 of 450 in In-Ear Headphones | #425 of 450 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 54 (measured by crinacle, via AutoEQ) | 53 (measured by oratory1990, via AutoEQ) |
| Deviation From Target | 3.18 dB standard deviation | 3.59 dB standard deviation |
| Tonal Tilt | -1.30 (negative is warmer, positive brighter) | -0.43 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+2.9 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (+5.6 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Hybrid (1 dynamic + 7 balanced armature) | Dynamic |
| Drivers | 1 x 10mm dynamic + 7 x balanced armature | 1 x dynamic |
| Impedance | 24 ohms | 16 ohms |
| Sensitivity | 109 dB | 106 dB SPL/V |
| Frequency Response | 10Hz - 40kHz (Manufacturer specified) | 40Hz - 20kHz (Manufacturer specified) |
Related Headphone Comparisons
How KZ ZAS compares with other leading options:
- Sennheiser CX 3.00 vs KZ ZAS
- iBasso IT01 vs KZ ZAS
- KZ ZAS vs CCA PLA13
- CCA PLA13 vs Sennheiser IE 4
- Questyle NHB12 vs Sennheiser IE 4
Prices on this page were last checked October 11, 2026 at 4:59 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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The Two Headphones In Full
KZ ZAS: $75.99 Amazon eBay
Pros: Bass is lifted about 2 to 3 dB from 20 to 200 Hz, so bass-heavy genres have plenty of weight, and listeners with a bassy or warm taste are the best match. It packs one 10 mm dynamic driver and seven balanced armatures per side. Sensitivity of 109 dB means any phone drives it easily.
Cons: In hobbyist measurements on squig.link the presence range sits about 5.4 dB below target with a 7.5 dB dip near 3.4 kHz, which pushes vocals back and blurs detail. A 5.5 dB peak near 11.9 kHz adds a thin, sizzly edge on top. The Final Audio E3000 carries a higher rating for less money.
Full KZ ZAS review and specifications →
| Released | 2021 (5 years ago) |
|---|---|
| Back | Closed |
| Connection | Wired |
| Deviation From Target | 3.18 dB standard deviation |
| Driver Type | Hybrid (1 dynamic + 7 balanced armature) |
| Drivers | 1 x 10mm dynamic + 7 x balanced armature |
| Form Factor | In-ear |
| Frequency Response | 10Hz - 40kHz (Manufacturer specified) |
| Harman Preference Score | 54 (measured by crinacle, via AutoEQ) |
| Impedance | 24 ohms |
| Sensitivity | 109 dB |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+2.9 dB at 30 Hz) |
| Tonal Tilt | -1.30 (negative is warmer, positive brighter) |
EQ preset to match the Harman target
Set a preamp of -5.1 dB, then add these filters in any parametric equalizer (Wavelet, Equalizer APO, Peace, or a player with parametric EQ). Calculated by AutoEQ from its measured frequency response.
| Filter | Frequency | Gain | Q |
|---|---|---|---|
| Low shelf | 105 Hz | -3.8 dB | 0.70 |
| Peak | 3,021 Hz | +20.0 dB | 0.67 |
| Peak | 177 Hz | -3.3 dB | 1.06 |
| Peak | 2,306 Hz | -20.0 dB | 0.65 |
| Peak | 801 Hz | +4.7 dB | 0.87 |
| High shelf | 10,000 Hz | +2.2 dB | 0.70 |
| Peak | 68 Hz | +0.7 dB | 1.83 |
| Peak | 5,877 Hz | -2.8 dB | 5.99 |
| Peak | 115 Hz | -0.5 dB | 2.49 |
| Peak | 5,429 Hz | +1.5 dB | 6.00 |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
Sennheiser IE 4: $89.00 B&H Photo Video eBay
Pros: Sub-bass and bass both sit more than 6 dB above target and extend fully to 20 Hz, a good match for listeners who want big, rumbling bass and a V shaped sound. The 16 ohm impedance and 106 dB/V sensitivity let it run fine from a phone. It is rated level with the CCA PLA13 at a similar price.
Cons: A huge 15.3 dB peak near 5.1 kHz and presence about 10 dB above target make vocals and snares sound shouty and fatiguing. The KZ ZAS is rated higher and costs less.
Full Sennheiser IE 4 review and specifications →
| Released | 2005 (21 years ago) |
|---|---|
| Back | Closed |
| Connection | Wired |
| Deviation From Target | 3.59 dB standard deviation |
| Driver Type | Dynamic |
| Drivers | 1 x dynamic |
| Form Factor | In-ear |
| Frequency Response | 40Hz - 20kHz (Manufacturer specified) |
| Harman Preference Score | 53 (measured by oratory1990, via AutoEQ) |
| Impedance | 16 ohms |
| Sensitivity | 106 dB SPL/V |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+5.6 dB at 30 Hz) |
| Tonal Tilt | -0.43 (negative is warmer, positive brighter) |
EQ preset to match the Harman target
Set a preamp of -5.2 dB, then add these filters in any parametric equalizer (Wavelet, Equalizer APO, Peace, or a player with parametric EQ). Calculated by AutoEQ from its measured frequency response.
| Filter | Frequency | Gain | Q |
|---|---|---|---|
| Low shelf | 105 Hz | -3.3 dB | 0.70 |
| Peak | 1,393 Hz | +6.5 dB | 0.39 |
| Peak | 4,512 Hz | -13.3 dB | 0.97 |
| Peak | 8,609 Hz | +6.4 dB | 1.20 |
| Peak | 200 Hz | -2.3 dB | 1.14 |
| High shelf | 10,000 Hz | -1.0 dB | 0.70 |
| Peak | 2,324 Hz | +2.4 dB | 3.14 |
| Peak | 3,227 Hz | -4.2 dB | 4.39 |
| Peak | 64 Hz | +0.9 dB | 2.17 |
| Peak | 4,107 Hz | +2.7 dB | 6.00 |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons