Short answer: the Fosi Audio IM4. Both are rated 4.3/5 for sound quality (#133 and #152 of 450 in-ear headphones), and the Fosi Audio IM4 costs $99.99 against $109 for the ZhuLinNiao Z4, so with nothing between them on sound quality, price settles it.
Buy the Fosi Audio IM4. Both are rated the same for sound quality, and it costs $9.01 less than the ZhuLinNiao Z4.
Still deciding? The full Headphones rankings cover every ranked option.
Specifications Side By Side
| Fosi Audio IM4 | ZhuLinNiao Z4 | |
|---|---|---|
| Price | $99.99 | $109.00 |
| Ranked | #133 of 450 in In-Ear Headphones | #152 of 450 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 78 (median of 5 squig.link measurements, calibrated to AutoEQ) | 77 (median of 10 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 1.75 dB standard deviation | 1.69 dB standard deviation |
| Tonal Tilt | -0.02 (negative is warmer, positive brighter) | +0.44 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-1.4 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (-3.7 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Dynamic | Dynamic |
| Drivers | 1 x 10mm dynamic | - |
| Impedance | 21 ohms | 32 ohms |
| Sensitivity | 109 dB | 106 dB |
| Weight | 0 lbs (7 g) per earbud | - |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) | 10Hz - 40kHz (Manufacturer specified) |
| Built-in Microphone | No | - |
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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
Fosi Audio IM4: $99.99 Amazon eBay
Full Fosi Audio IM4 review and specifications →
| Released | 2025 (1 year ago) |
|---|---|
| Back | Closed |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 1.75 dB standard deviation |
| Driver Type | Dynamic |
| Drivers | 1 x 10mm dynamic |
| Form Factor | In-ear |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) |
| Harman Preference Score | 78 (median of 5 squig.link measurements, calibrated to AutoEQ) |
| Impedance | 21 ohms |
| Sensitivity | 109 dB |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-1.4 dB at 30 Hz) |
| Tonal Tilt | -0.02 (negative is warmer, positive brighter) |
| Weight | 0 lbs (7 g) per earbud |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
ZhuLinNiao Z4: $109.00 Amazon eBay
Full ZhuLinNiao Z4 review and specifications →
| Back | Closed |
|---|---|
| Connection | Wired |
| Deviation From Target | 1.69 dB standard deviation |
| Driver Type | Dynamic |
| Form Factor | In-ear |
| Frequency Response | 10Hz - 40kHz (Manufacturer specified) |
| Harman Preference Score | 77 (median of 10 squig.link measurements, calibrated to AutoEQ) |
| Impedance | 32 ohms |
| Sensitivity | 106 dB |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-3.7 dB at 30 Hz) |
| Tonal Tilt | +0.44 (negative is warmer, positive brighter) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons