Short answer: the OpenAudio Mercury. It ranks #370 of 450 in-ear headphones by sound quality, rated 3.3/5, at $599.99; the Fatfreq Reference Pro SE ranks #392, rated 3.0/5, at $599. With prices this close, go by the sound-quality ranking rather than the cost.
The case for the OpenAudio Mercury: A bass-forward tuning with about 4.7 dB of extra sub-bass below 60 Hz and a 5.8 dB lift at 30 Hz, so kick drums and synth bass carry deep rumble. The tradeoff: A 6.6 dB dip near 5.9 kHz in squig.link measurements softens vocal consonants and the leading edge of guitars and snares.
Why pick the Fatfreq Reference Pro SE: It is a wired, closed-back in-ear that blocks outside noise passively. Watch for: In crinacle’s measurement it scores only 62.0 for preference, with a 3.18 dB deviation from target, so the tuning departs noticeably from what most listeners prefer.
Buy the OpenAudio Mercury. It is rated higher for sound quality, and the $0.99 you would save on the Fatfreq Reference Pro SE does not close the gap.
Looking for alternatives? See the complete Headphones rankings.
Specifications Side By Side
| OpenAudio Mercury | Fatfreq Reference Pro SE | |
|---|---|---|
| Price | $599.99 | $599.00 |
| Ranked | #370 of 450 in In-Ear Headphones | #392 of 450 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 65 (measured by crinacle, via AutoEQ) | 62 (measured by crinacle, via AutoEQ) |
| Deviation From Target | 2.46 dB standard deviation | 3.18 dB standard deviation |
| Tonal Tilt | -1.07 (negative is warmer, positive brighter) | +0.31 (negative is warmer, positive brighter) |
| Connection | Wired | Wired |
| Driver Type | Hybrid (1 dynamic + 4 balanced armature) | - |
| Drivers | 1 x 9.2mm dynamic + 4 x balanced armature | - |
| Impedance | 8 ohms | - |
| Sensitivity | 110 dB/mW | - |
| Frequency Response | 5Hz - 40kHz (Manufacturer specified) | 20Hz - 20kHz (Manufacturer specified) |
| Built-in Microphone | No | - |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+5.8 dB at 30 Hz) | - |
Related Headphone Comparisons
How OpenAudio Mercury compares with other leading options:
- Sennheiser IE 600 vs OpenAudio Mercury
- OpenAudio Mercury vs Shanling ME700
- Fatfreq Reference Pro SE vs Shanling ME700
- Fatfreq Reference Pro SE vs Yanyin Mahina
- Fatfreq Reference Pro SE vs Audio-Technica ATH-CK2000Ti
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
OpenAudio Mercury: $599.99 Shenzhenaudio eBay
Pros: A bass-forward tuning with about 4.7 dB of extra sub-bass below 60 Hz and a 5.8 dB lift at 30 Hz, so kick drums and synth bass carry deep rumble. The midrange from 200 Hz to 3 kHz tracks target within half a decibel, keeping vocals natural. A 9.2mm dynamic woofer and four balanced armatures at 110 dB/mW play loud from a phone.
Cons: A 6.6 dB dip near 5.9 kHz in squig.link measurements softens vocal consonants and the leading edge of guitars and snares. The Fearless Audio S8F rates higher for less money, and the Fearless Audio S6Rui matches its rating for considerably less.
Full OpenAudio Mercury review and specifications →
| Released | 2022 (4 years ago) |
|---|---|
| Back | Closed |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 2.46 dB standard deviation |
| Driver Type | Hybrid (1 dynamic + 4 balanced armature) |
| Drivers | 1 x 9.2mm dynamic + 4 x balanced armature |
| Form Factor | In-ear |
| Frequency Response | 5Hz - 40kHz (Manufacturer specified) |
| Harman Preference Score | 65 (measured by crinacle, via AutoEQ) |
| Impedance | 8 ohms |
| Sensitivity | 110 dB/mW |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+5.8 dB at 30 Hz) |
| Tonal Tilt | -1.07 (negative is warmer, positive brighter) |
EQ preset to match the Harman target
Set a preamp of -5.8 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 | -3.5 dB | 0.70 |
| Peak | 8,898 Hz | +5.0 dB | 0.59 |
| Peak | 1,655 Hz | -4.0 dB | 1.64 |
| Peak | 190 Hz | -1.7 dB | 1.58 |
| Peak | 766 Hz | +1.6 dB | 1.15 |
| High shelf | 10,000 Hz | -5.2 dB | 0.70 |
| Peak | 69 Hz | +1.4 dB | 2.47 |
| Peak | 4,352 Hz | -3.9 dB | 5.29 |
| Peak | 3,442 Hz | +2.2 dB | 4.15 |
| Peak | 5,697 Hz | +3.1 dB | 5.70 |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
Fatfreq Reference Pro SE: $599.00 FATfreq eBay
Pros: It is a wired, closed-back in-ear that blocks outside noise passively. It holds an equal rating to the Cayin Fantasy and the Shanling ME700.
Cons: In crinacle’s measurement it scores only 62.0 for preference, with a 3.18 dB deviation from target, so the tuning departs noticeably from what most listeners prefer. The equally rated Cayin Fantasy costs less.
Full Fatfreq Reference Pro SE review and specifications →
| Released | 2022 (4 years ago) |
|---|---|
| Back | Closed |
| Connection | Wired |
| Deviation From Target | 3.18 dB standard deviation |
| Form Factor | In-ear |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) |
| Harman Preference Score | 62 (measured by crinacle, via AutoEQ) |
| Tonal Tilt | +0.31 (negative is warmer, positive brighter) |
EQ preset to match the Harman target
Set a preamp of -7.8 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 | +8.5 dB | 0.70 |
| Peak | 78 Hz | -4.1 dB | 0.20 |
| Peak | 996 Hz | +3.3 dB | 0.84 |
| Peak | 1,675 Hz | -4.1 dB | 1.47 |
| Peak | 9,708 Hz | +6.2 dB | 0.76 |
| High shelf | 10,000 Hz | +3.3 dB | 0.70 |
| Peak | 5,897 Hz | +2.6 dB | 6.00 |
| Peak | 4,550 Hz | -1.9 dB | 3.96 |
| Peak | 7,117 Hz | -2.9 dB | 5.77 |
| Peak | 5,664 Hz | +0.7 dB | 4.21 |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons