Short answer: the AKG K712. Both are rated 3.8/5 for sound quality (#100 and #94 of 216 over-ear headphones), and the AKG K712 costs $465 against $479.95 for the Sennheiser HD 660S2, so with nothing between them on sound quality, price settles it.
What the AKG K712 does well: The open back gives a wide, airy presentation with a flat midrange, presence and treble within about 0.3 dB of the target between 3 and 10 kHz. The catch: Sub-bass is about 3.7 dB under target and the low mids are about 3 dB hot, so music sounds a touch thick in the midrange while the deepest bass lacks rumble.
Why pick the Sennheiser HD 660S2: 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. Watch for: 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 AKG K712. Both are rated the same for sound quality, and it costs $14.95 less than the Sennheiser HD 660S2.
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Specifications Side By Side
| AKG K712 | Sennheiser HD 660S2 | |
|---|---|---|
| Price | $465.00 | $479.95 |
| Ranked | #100 of 216 in Over-Ear Headphones | #94 of 216 in Over-Ear Headphones |
| Form Factor | Over-ear | Over-ear |
| Harman Preference Score | 77 (measured by oratory1990, via AutoEQ) | 78 (measured by oratory1990, via AutoEQ) |
| Deviation From Target | 2.51 dB standard deviation | 2.36 dB standard deviation |
| Tonal Tilt | -0.40 (negative is warmer, positive brighter) | -0.43 (negative is warmer, positive brighter) |
| Sub-bass Extension | Falls 6 dB below target at 34 Hz (-6.5 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 | Dynamic | Dynamic |
| Impedance | 62 ohms | 300 ohms |
| Sensitivity | 105 dB/mW | 104 dB SPL/V |
| Weight | 0.5 lbs (235 g) | 0.6 lbs (260 g) |
| Frequency Response | 10Hz - 39.8kHz | 8Hz - 41.5kHz (Manufacturer specified) |
| Drivers | - | 1 x 38mm dynamic |
| Built-in Microphone | - | No |
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More worthwhile head-to-heads for Sennheiser HD 660S2:
- HIFIMAN Edition XV vs Sennheiser HD 660S2
- Moondrop Para 2 vs Sennheiser HD 660S2
- Moondrop Para 2 vs AKG K712
- AKG K712 vs Focal Azurys
- HIFIMAN Edition XV vs AKG K712
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The Two Headphones In Full
AKG K712: $465.00 Amazon eBay
Pros: The open back gives a wide, airy presentation with a flat midrange, presence and treble within about 0.3 dB of the target between 3 and 10 kHz. Bass from 60 to 200 Hz is about 1.4 dB warm, which adds a little body. At 235 g it is light, and 105 dB/mW sensitivity is high for a 62 ohm design.
Cons: Sub-bass is about 3.7 dB under target and the low mids are about 3 dB hot, so music sounds a touch thick in the midrange while the deepest bass lacks rumble. A 6 dB dip near 9.4 kHz and a 3.8 dB peak near 5.9 kHz make treble slightly uneven. The open design leaks sound and offers no isolation, and the Austrian Audio Hi-X65 matches its rating for a lower price.
Full AKG K712 review and specifications →
| Back | Open |
|---|---|
| Connection | Wired |
| Deviation From Target | 2.51 dB standard deviation |
| Driver Type | Dynamic |
| Form Factor | Over-ear |
| Frequency Response | 10Hz - 39.8kHz |
| Harman Preference Score | 77 (measured by oratory1990, via AutoEQ) |
| Impedance | 62 ohms |
| Sensitivity | 105 dB/mW |
| Sub-bass Extension | Falls 6 dB below target at 34 Hz (-6.5 dB at 30 Hz) |
| Tonal Tilt | -0.40 (negative is warmer, positive brighter) |
| Weight | 0.5 lbs (235 g) |
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 | +6.9 dB | 0.70 |
| Peak | 143 Hz | -3.6 dB | 0.23 |
| Peak | 1,217 Hz | +5.0 dB | 1.43 |
| Peak | 3,049 Hz | +4.8 dB | 3.18 |
| Peak | 2,178 Hz | -3.4 dB | 3.30 |
| High shelf | 10,000 Hz | -0.3 dB | 0.70 |
| Peak | 5,868 Hz | -2.6 dB | 5.87 |
| Peak | 67 Hz | -0.6 dB | 1.75 |
| Peak | 157 Hz | +0.9 dB | 1.87 |
| Peak | 243 Hz | -0.5 dB | 2.27 |
- 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