Short answer: the HIFIMAN Edition XV. It ranks #84 of 216 over-ear headphones by sound quality, rated 3.9/5, at $399; the Sennheiser HD 660S2 ranks #94, rated 3.8/5, and costs $479.95, so there is little reason to consider the other one.
What the HIFIMAN Edition XV does well: Its open back planar driver scores 79.8 for preference in the median of 8 squig.link measurements, a strong result for an open headphone. Watch for: An 8.7 dB dip near 9.7 kHz dulls cymbal shimmer and sibilance, and sub-bass falls about 4 dB short below 60 Hz, as open planars often do.
What the Sennheiser HD 660S2 does well: Oratory1990’s measurement gives it a preference score of 78 with a smooth midrange, as the band from 200 Hz to 6 kHz stays within about 1.4 dB of the Harman target and the largest peak above 1.5 kHz is under 2 dB. The tradeoff: Sub-bass falls about 6.5 dB below target and is 6 dB short by 40 Hz, and an open back means bass is felt less and sound leaks out freely.
Buy the HIFIMAN Edition XV. It is rated higher for sound quality than the Sennheiser HD 660S2 and costs less, so it is the default pick unless a specific strength of the other one matters more to you.
Still deciding? The full Headphones rankings cover every ranked option.
Specifications Side By Side
| HIFIMAN Edition XV | Sennheiser HD 660S2 | |
|---|---|---|
| Price | $399.00 | $479.95 |
| Ranked | #84 of 216 in Over-Ear Headphones | #94 of 216 in Over-Ear Headphones |
| Form Factor | Over-ear | Over-ear |
| Harman Preference Score | 79 (median of 9 squig.link measurements, calibrated to AutoEQ) | 78 (measured by oratory1990, via AutoEQ) |
| Deviation From Target | 2.18 dB standard deviation | 2.36 dB standard deviation |
| Tonal Tilt | -0.44 (negative is warmer, positive brighter) | -0.43 (negative is warmer, positive brighter) |
| Sub-bass Extension | Falls 6 dB below target at 27 Hz (-5.8 dB at 30 Hz) | Falls 6 dB below target at 40 Hz (-7.4 dB at 30 Hz) |
| Connection | Wired | Wired |
| Back | Open | Open |
| Driver Type | Planar magnetic | Dynamic |
| Impedance | 12 ohms | 300 ohms |
| Sensitivity | 92 dB | 104 dB SPL/V |
| Weight | 1 lbs (452 g) | 0.6 lbs (260 g) |
| Frequency Response | 8Hz - 50kHz (Manufacturer specified) | 8Hz - 41.5kHz (Manufacturer specified) |
| Built-in Microphone | No | No |
| Drivers | - | 1 x 38mm dynamic |
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More worthwhile head-to-heads for HIFIMAN Edition XV:
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- Logitech G Astro A50 X vs HIFIMAN Edition XV
- HIFIMAN Edition XV vs AKG K712
- HIFIMAN Edition XV vs Sennheiser HD 490 Pro
- AKG K712 vs Sennheiser HD 660S2
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
HIFIMAN Edition XV: $399.00 Amazon eBay
Pros: Its open back planar driver scores 79.8 for preference in the median of 8 squig.link measurements, a strong result for an open headphone. Bass from 60 to 200 Hz sits right on target, so bass guitar and cello come through full and clean. A gentle warm tilt and a 2.3 dB lift in the 10 to 16 kHz air band keep it airy without harshness.
Cons: An 8.7 dB dip near 9.7 kHz dulls cymbal shimmer and sibilance, and sub-bass falls about 4 dB short below 60 Hz, as open planars often do. Sensitivity of 92 dB is low for an over-ear, so a phone will struggle and a desktop amp is the better partner. The open back leaks sound and blocks no outside noise, and the 452 g weight is heavy. See headphone amps and DACs with enough power to drive it.
Full HIFIMAN Edition XV review and specifications →
| Released | Sep 2025 (1 year ago) |
|---|---|
| Back | Open |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 2.18 dB standard deviation |
| Driver Type | Planar magnetic |
| Form Factor | Over-ear |
| Frequency Response | 8Hz - 50kHz (Manufacturer specified) |
| Harman Preference Score | 79 (median of 9 squig.link measurements, calibrated to AutoEQ) |
| Impedance | 12 ohms |
| Sensitivity | 92 dB |
| Sub-bass Extension | Falls 6 dB below target at 27 Hz (-5.8 dB at 30 Hz) |
| Tonal Tilt | -0.44 (negative is warmer, positive brighter) |
| Weight | 1 lbs (452 g) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
Sennheiser HD 660S2: $479.95 B&H Photo Video eBay
Pros: Oratory1990’s measurement gives it a preference score of 78 with a smooth midrange, as the band from 200 Hz to 6 kHz stays within about 1.4 dB of the Harman target and the largest peak above 1.5 kHz is under 2 dB. Voices, strings and piano come across natural and free of harshness. The gently warm balance suits long listening sessions at home.
Cons: Sub-bass falls about 6.5 dB below target and is 6 dB short by 40 Hz, and an open back means bass is felt less and sound leaks out freely. A 7.9 dB dip near 9.3 kHz dulls cymbal shimmer, and its 300 ohm impedance with 104 dB/V sensitivity calls for a dedicated headphone amp. The cheaper Austrian Audio Hi-X65 rates the same. See headphone amps and DACs with enough power to drive it.
Full Sennheiser HD 660S2 review and specifications →
| Released | Feb 2023 (3 years ago) |
|---|---|
| Back | Open |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 2.36 dB standard deviation |
| Driver Type | Dynamic |
| Drivers | 1 x 38mm dynamic |
| Form Factor | Over-ear |
| Frequency Response | 8Hz - 41.5kHz (Manufacturer specified) |
| Harman Preference Score | 78 (measured by oratory1990, via AutoEQ) |
| Impedance | 300 ohms |
| Sensitivity | 104 dB SPL/V |
| Sub-bass Extension | Falls 6 dB below target at 40 Hz (-7.4 dB at 30 Hz) |
| Tonal Tilt | -0.43 (negative is warmer, positive brighter) |
| Weight | 0.6 lbs (260 g) |
EQ preset to match the Harman target
Set a preamp of -6.4 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 | +7.6 dB | 0.70 |
| Peak | 98 Hz | -3.5 dB | 0.31 |
| Peak | 8,089 Hz | +4.7 dB | 0.53 |
| Peak | 5,567 Hz | -6.6 dB | 3.92 |
| Peak | 1,206 Hz | -2.0 dB | 2.46 |
| High shelf | 10,000 Hz | -3.8 dB | 0.70 |
| Peak | 2,218 Hz | +1.1 dB | 3.75 |
| Peak | 3,206 Hz | -1.2 dB | 3.51 |
| Peak | 4,367 Hz | +1.3 dB | 6.00 |
| Peak | 115 Hz | +0.1 dB | 1.26 |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons