Short answer: the Sennheiser IE 600. It ranks #357 of 450 in-ear headphones by sound quality, rated 3.5/5, at $699.95. The OpenAudio Mercury ranks #370, rated 3.3/5, at $599.99, $99.96 cheaper, which does not close the gap in sound quality.
Why pick the Sennheiser IE 600: Sub-bass extends to 20 Hz with a slight 1.7 dB lift, and bass, low mids and upper mids all sit within about 1.3 dB of target, so the core of most music sounds full and natural. The tradeoff: In oratory1990’s measurement a 7.6 dB dip near 5.9 kHz and a presence band 5.5 dB under target take bite out of vocals and guitars, while a 4.7 dB peak near 9.7 kHz can sound sharp.
Why pick 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 catch: A 6.6 dB dip near 5.9 kHz in squig.link measurements softens vocal consonants and the leading edge of guitars and snares.
Buy the Sennheiser IE 600. It is rated higher for sound quality, and the $99.96 you would save on the OpenAudio Mercury does not close the gap.
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Specifications Side By Side
| Sennheiser IE 600 | OpenAudio Mercury | |
|---|---|---|
| Price | $699.95 | $599.99 |
| Ranked | #357 of 450 in In-Ear Headphones | #370 of 450 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 67 (measured by oratory1990, via AutoEQ) | 65 (measured by crinacle, via AutoEQ) |
| Deviation From Target | 2.46 dB standard deviation | 2.46 dB standard deviation |
| Tonal Tilt | -0.80 (negative is warmer, positive brighter) | -1.07 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+2.3 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (+5.8 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Dynamic | Hybrid (1 dynamic + 4 balanced armature) |
| Drivers | 1 x 7mm dynamic | 1 x 9.2mm dynamic + 4 x balanced armature |
| Impedance | 18 ohms | 8 ohms |
| Sensitivity | 118 dB SPL/V | 110 dB/mW |
| Frequency Response | 4Hz - 46.5kHz (Manufacturer specified) | 5Hz - 40kHz (Manufacturer specified) |
| Built-in Microphone | No | No |
| Weight | 0 lbs (6 g) per earbud | - |
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- Sennheiser IE 600 vs Sennheiser IE 900
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
Sennheiser IE 600: $699.95 B&H Photo Video eBay
Pros: Sub-bass extends to 20 Hz with a slight 1.7 dB lift, and bass, low mids and upper mids all sit within about 1.3 dB of target, so the core of most music sounds full and natural. Air above 10 kHz is lifted about 5.6 dB, adding sparkle to cymbals and room sound. At 118 dB/V it is easy to drive from a phone, and it suits listeners who like a bassy or warm tilt.
Cons: In oratory1990’s measurement a 7.6 dB dip near 5.9 kHz and a presence band 5.5 dB under target take bite out of vocals and guitars, while a 4.7 dB peak near 9.7 kHz can sound sharp. The FiiO FD5 and iBasso IT04 both carry higher ratings for considerably less money.
Full Sennheiser IE 600 review and specifications →
| Released | Mar 2022 (4 years ago) |
|---|---|
| Back | Closed |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 2.46 dB standard deviation |
| Driver Type | Dynamic |
| Drivers | 1 x 7mm dynamic |
| Form Factor | In-ear |
| Frequency Response | 4Hz - 46.5kHz (Manufacturer specified) |
| Harman Preference Score | 67 (measured by oratory1990, via AutoEQ) |
| Impedance | 18 ohms |
| Sensitivity | 118 dB SPL/V |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (+2.3 dB at 30 Hz) |
| Tonal Tilt | -0.80 (negative is warmer, positive brighter) |
| Weight | 0 lbs (6 g) per earbud |
EQ preset to match the Harman target
Set a preamp of -5.3 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 | -2.7 dB | 0.70 |
| Peak | 4,374 Hz | +5.0 dB | 1.28 |
| Peak | 196 Hz | -1.9 dB | 1.50 |
| Peak | 1,727 Hz | -2.8 dB | 1.16 |
| Peak | 798 Hz | +1.5 dB | 1.45 |
| High shelf | 10,000 Hz | -7.6 dB | 0.70 |
| Peak | 72 Hz | +1.4 dB | 1.93 |
| Peak | 5,857 Hz | +3.3 dB | 5.80 |
| Peak | 143 Hz | -0.7 dB | 3.18 |
| Peak | 4,796 Hz | -0.6 dB | 4.12 |
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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