Short answer: a tie on sound quality. Both are rated 4.3/5 (#133 and #157 of 450 in-ear headphones) at nearly the same price ($99.99 vs $99.99), so choose on features and fit.
Buy the Fosi Audio IM4 or the Juzear Defiant on features: they are rated the same for sound quality at close to the same price.
Want more options? Browse the full Headphones rankings.
Specifications Side By Side
| Fosi Audio IM4 | Juzear Defiant | |
|---|---|---|
| Price | $99.99 | $99.99 |
| Ranked | #133 of 450 in In-Ear Headphones | #157 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 5 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 1.75 dB standard deviation | 1.54 dB standard deviation |
| Tonal Tilt | -0.02 (negative is warmer, positive brighter) | -0.58 (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 (+0.4 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Dynamic | Hybrid (1 dynamic + 3 balanced armature) |
| Drivers | 1 x 10mm dynamic | 1 x dynamic + 3 x balanced armature |
| Impedance | 21 ohms | 32 ohms |
| Sensitivity | 109 dB | 109 dB |
| Weight | 0 lbs (7 g) per earbud | - |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) | 20Hz - 20kHz (Manufacturer specified) |
| Built-in Microphone | No | - |
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- Fosi Audio IM4 vs ZhuLinNiao Z4
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
Juzear Defiant: $99.99 Amazon eBay
Full Juzear Defiant review and specifications →
| Released | Apr 2025 (1 year ago) |
|---|---|
| Back | Closed |
| Connection | Wired |
| Deviation From Target | 1.54 dB standard deviation |
| Driver Type | Hybrid (1 dynamic + 3 balanced armature) |
| Drivers | 1 x dynamic + 3 x balanced armature |
| Form Factor | In-ear |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) |
| Harman Preference Score | 77 (median of 5 squig.link measurements, calibrated to AutoEQ) |
| Impedance | 32 ohms |
| Sensitivity | 109 dB |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+0.4 dB at 30 Hz) |
| Tonal Tilt | -0.58 (negative is warmer, positive brighter) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons