Short answer: a tie on sound quality. Both are rated 4.3/5 (#133 and #135 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 Moondrop Rays on features: they are rated the same for sound quality at close to the same price.
Still deciding? The full Headphones rankings cover every ranked option.
Specifications Side By Side
| Fosi Audio IM4 | Moondrop Rays | |
|---|---|---|
| Price | $99.99 | $99.99 |
| Ranked | #133 of 450 in In-Ear Headphones | #135 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) | 78 (median of 4 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 1.75 dB standard deviation | 1.53 dB standard deviation |
| Tonal Tilt | -0.02 (negative is warmer, positive brighter) | -0.41 (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 (-1.2 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Dynamic | Hybrid (1 dynamic + 1 planar magnetic) |
| Drivers | 1 x 10mm dynamic | 1 x 10mm dynamic + 1 x 6mm planar magnetic |
| Impedance | 21 ohms | 30 ohms |
| Sensitivity | 109 dB | 120 dB SPL/Vrms |
| Weight | 0 lbs (7 g) per earbud | - |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) | 7Hz - 39kHz (Manufacturer specified) |
| Built-in Microphone | No | Yes |
Related Headphone Comparisons
More worthwhile head-to-heads for Fosi Audio IM4:
- 7Hz Salnotes Dioko vs Fosi Audio IM4
- Oriveti Bleqk Dynabird vs Fosi Audio IM4
- Fosi Audio IM4 vs Moondrop Kato
- Fosi Audio IM4 vs ZhuLinNiao Z4
- Fosi Audio IM4 vs Juzear Defiant
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.
As an eBay Partner, we may be compensated if you make a purchase.
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
Moondrop Rays: $99.99 Amazon eBay
Full Moondrop Rays review and specifications →
| Released | Apr 2025 (1 year ago) |
|---|---|
| Back | Closed |
| Built-in Microphone | Yes |
| Connection | Wired |
| Deviation From Target | 1.53 dB standard deviation |
| Driver Type | Hybrid (1 dynamic + 1 planar magnetic) |
| Drivers | 1 x 10mm dynamic + 1 x 6mm planar magnetic |
| Form Factor | In-ear |
| Frequency Response | 7Hz - 39kHz (Manufacturer specified) |
| Harman Preference Score | 78 (median of 4 squig.link measurements, calibrated to AutoEQ) |
| Impedance | 30 ohms |
| Sensitivity | 120 dB SPL/Vrms |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-1.2 dB at 30 Hz) |
| Tonal Tilt | -0.41 (negative is warmer, positive brighter) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons