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- Table of Contents
- Top
- Main Differences
- Sound
- Design
- Isolation
- Microphone
- Active Features
- Connectivity
- Comments
Sennheiser HD 660 S vs HiFiMan Sundara 2020
Side-by-Side Comparison
Products
Sennheiser HD 660 S
HiFiMan Sundara 2020
Tested using Methodology v1.5
Updated Jun 27, 2024 03:04 PM
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Amazon.comTested using Methodology v2.0
Updated Apr 24, 2025 06:41 PM
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Amazon.com
TypeOver-ear
Noise CancellingNo
EnclosureOpen-Back
WirelessNo
TransducerDynamic
MicNo
TypeOver-Ear
Noise CancellingNo
EnclosureOpen-Back
Bass AmountSlightly Underemphasized (-3 dB)
WirelessNo
TransducerPlanar Magnetic
Treble AmountSlightly Underemphasized (-2 dB)
MicNo
Sound SignatureFlat
Variants
- HD 660 S
- Sundara 2020 (Black)
Our Verdict
Sennheiser HD 660 S
HiFiMan Sundara 2020
The HiFiMan Sundara 2020 and the Sennheiser HD 660 S are both over-ear headphones designed for critical listening. The HiFiMan do a better job at producing low-bass with more thump and punch than the Sennheiser, as well as treble with a little more clarity and detail. That said, both are very well-balanced throughout the mid-range, so vocals and instruments should sound present without being honky. Though they are both open-backs, the HiFiMan have a significantly more speaker-like passive soundstage and are more comfortable than the Sennheiser, but the latter are more stable on the head, which might be important if you like to headbang while listening to music.
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Standard
HD 660 S
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Sundara 2020
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HD 660 S
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Sundara 2020
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HD 660 S
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Sundara 2020
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HD 660 S
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Sundara 2020
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HD 660 S
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Sundara 2020
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Finding storeMain Differences forNeutral Sound
Neutral Sound
Threshold
Neutral Sound
7.9
Full Comparison
Sound
Sound Profile
Sound Profile
Normalization Frequency
650 Hz
Bass Amount
Slightly Underemphasized (-3 dB)
Bass Amount
-4.39 dB
Treble Amount
-3.29 dB
Treble Amount
Slightly Underemphasized (-2 dB)
Sound Signature
Flat
Frequency Response Consistency
8.0
7.9
Consistency L
Consistency R
Avg. Std. Deviation
0.4 dB
0.88 dB
Raw Frequency Response
Bass Profile: Target Compliance
7.0
8.0
Bass Profile: Target Compliance
RMS Deviation From Target
4.08 dB
4.3 dB
Low-Frequency Extension
82.34 Hz
22.68 Hz
Low Bass
-7.93 dB
-6 dB
Mid Bass
-2.51 dB
-2.37 dB
High Bass
1.35 dB
0.06 dB
Mid-Range Profile: Target Compliance
9.4
9.0
Mid-Range Profile: Target Compliance
RMS Deviation From Target
0.77 dB
1.4 dB
Low Mid
0.8 dB
0.56 dB
Mid-Mid
0.13 dB
0.04 dB
High Mid
0.63 dB
-1.86 dB
Treble Profile: Target Compliance
7.1
9.3
Treble Profile: Target Compliance
RMS Deviation From Target
4.24 dB
2.19 dB
Low Treble
-2.45 dB
-2.53 dB
Mid Treble
-4.09 dB
-0.82 dB
High Treble
-10.04 dB
-4.67 dB
Peaks/Dips
8.1
7.9
Peaks/Dips Graph
Peaks
1.24 dB
1.1 dB
Dips
0.92 dB
1.85 dB
Stereo Mismatch
8.0
Frequency Response Mismatch
Phase Response Mismatch
Weighted Amplitude Mismatch
0.17
0.2 dB
Weighted Frequency Response Mismatch
1.23
1.2 dB
Weighted Phase Mismatch
2.25
2.1°
Cumulative Spectral Decay
CSD
PRTF
6.5
7.2
PRTF Accuracy (RMS Deviation)
2.89 dB
2.36 dB
PRTF Size (Avg.)
2.37 dB
4.77 dB
PRTF Distance
1.79 dB
9.84 dB
Openness
9.5
Acoustic Space Excitation
8.6
Harmonic Distortion
9.5
Harmonics Levels
WHD @ 94 dB SPL
0.193
0.04%
WHD @ 104 dB SPL
0.069
0.09%
Electrical Aspects
Impedance
Sensitivity @1kHz-1V
105.0 dB SPL
Bluetooth Max SPL
N/A
Virtual Soundstage
0.0
0.0
Virtual Soundstage
Head Modeling
No
No
Speaker Modeling
No
No
Room Ambience
No
No
Head Tracking
No
No
Virtual Surround
No App
No App
Test Settings
Firmware
No Firmware
No Firmware
Power
Passive
Passive
Connection
Wired
Wired
Codec
PCM, 24-bit, 48kHz
PCM, 24-bit, 48kHz
Test Instrument
Audio Precision APx517B
EQ
No EQ
No EQ
ANC
No ANC
No ANC
Tip/Pad
Default
Default
Microphone
No Microphone
No Microphone
Imaging
9.2
Group Delay
Phase Response Mismatch
Weighted Group Delay
0.2
Weighted Phase Mismatch
2.25
2.1°
Weighted Amplitude Mismatch
0.17
0.2 dB
Weighted Frequency Mismatch
1.23
1.2 dB
Weighted Harmonic Distortion
8.3
Weighted Harmonic Distortion
WHD @ 90
0.193
0.04%
WHD @ 100
0.069
0.09%
Design
Style
Design Picture 2
Type
Over-ear
Over-Ear
Enclosure
Open-Back
Open-Back
Wireless
No
No
Transducer
Dynamic
Planar Magnetic
Comfort
7.0
8.0
Comfort Picture
Weight
0.6 lbs
0.87 lbs
Clamping Force
1.2 lbs
1.6 lbs
Controls
0.0
0.0
Controls Picture
OS Compatibility
No Controls
No Controls
Ease Of Use
No Controls
No Controls
Feedback
No Controls
No Controls
Call/Music Control
No
No
Volume Control
No
No
Microphone Control
No
No
Channel Mixing
No
No
Noise Cancelling Control
No
No
Talk-Through
No
No
Additional Controls
No
No
Breathability
6.2
Breathability After Picture
Avg.Temp.Difference
6.4 °C
Portability
5.4
5.3
Portability Picture
L
7.7" (19.6 cm)
8.3" (21.1 cm)
W
7.1" (18.0 cm)
5.8" (14.7 cm)
H
3.6" (9.1 cm)
4.6" (11.7 cm)
Volume
197.00 in³ (3,228.24 cm³)
221.00 in³ (3,621.53 cm³)
Transmitter Required
No
No
Case
0.0
0.0
Case Picture
Type
No case
No case
L
N/A
N/A
W
N/A
N/A
H
N/A
N/A
Volume
N/A
N/A
Build Quality
7.5
7.5
Build Quality Picture
Stability
7.5
6.5
Stability Picture
Headshots 1
Angled Picture
Side Picture
Headshots 2
Front Picture
Rear Picture
Top
Top Picture
In The Box
In The Box Picture
Isolation
Noise Isolation - Full Range
1.3
0.6
Noise Isolation - Full Range Graph
Noise Cancelling
No
No
Overall Attenuation
-3.45 dB
-1.46 dB
Isolation Audio
Bass
0.02 dB
1.05 dB
Mid
0.86 dB
-0.31 dB
Treble
-10.94 dB
-5.78 dB
Noise Isolation - Common Scenarios
0.7
Noise Isolation - Common Scenarios Graph
Airplane Noise Attenuation
-2.06 dB
Airplane Noise Isolation Audio
Office Noise Attenuation
-1.14 dB
Office Noise Isolation Audio
Street Noise Attenuation
-1.01 dB
Street Noise Isolation Audio
Noise Isolation - Voice Handling
Female Voice 1
Male Voice 1
Female Voice 2
Male Voice 2
ANC Wind Handling
ANC Wind Handling Graph
ANC Wind Noise
N/A
Leakage
1.7
0.9
Leakage Audio
Overall Leakage @ 1ft
63.28 dB
66.5 dB
Microphone
Microphone Style
Integrated
No
No
In-Line
No
No
Boom
No
No
Detachable Boom
No
No
Mic
No
No
Recording Quality
0.0
0.0
Microphone Frequency Response
Recorded Speech
N/A
N/A
LFE
N/A
N/A
FR Std. Dev.
N/A
N/A
HFE
N/A
N/A
Weighted THD
N/A
N/A
Gain
N/A
N/A
Noise Handling
0.0
0.0
SpNR
SpNR
N/A
N/A
Noise Gate
No
No
Speech + Pink Noise Handling
N/A
N/A
Speech + Pink Noise Audio Sample
N/A
N/A
Speech + Subway Noise Handling
N/A
N/A
Speech + Subway Noise Audio Sample
N/A
N/A
Active Features
Battery
0.0
0.0
Battery Type
No Battery
No Battery
Continuous Battery Life
N/A
N/A
Additional Charges
N/A
N/A
Total Battery Life
N/A
N/A
Charge Time
N/A
N/A
Power-Saving Feature
No
No
Audio While Charging
No
No
Passive Playback
Passive Headphone
Passive Headphone
Charging Port
None
None
App Support
0.0
0.0
App Picture
App Name
No App
No App
iOS
No
No
Android
No
No
macOS
No
No
Windows
No
No
Equalizer
No
No
ANC Control
No
No
Mic Control
No
No
Room Effects
No
No
Playback Control
No
No
Button Mapping
No
No
Surround Support
No
No
Connectivity
Wired Connection
9.5
9.9
Cable Picture
Analog Audio
Yes
Yes
USB Audio
No
No
Detachable
Yes
Yes
Length
9.80 ft (2.99 m)
4.80 ft (1.46 m)
Connector
1/4" TRS
1/8" TRS
Latency - Analog
0.2 ms
Latency - USB
0 ms
N/A
Recorded Latency
Recorded Latency Connection
Analog
Bluetooth Connection
0.0
0.0
Bluetooth Version
No Bluetooth
No Bluetooth
Multi-Device Pairing
No
No
NFC Pairing
No
Quick Pair (Android)
No
Quick Pair (iOS)
No
Line Of Sight Range
N/A
N/A
Latency - SBC
N/A
N/A
Latency - aptX
N/A
N/A
Latency - aptX Adaptive (High Quality)
N/A
Latency - aptX Adaptive (Low Latency)
N/A
Latency - LDAC
N/A
Recorded Latency
N/A
Recorded Latency Codec
No Bluetooth Audio
AAC Support
No
PC Latency (aptX HD)
N/A
PC Latency (aptX-LL)
N/A
iOS Latency
N/A
Android Latency
N/A
Wireless Connection (Dongle)
0.0
0.0
Line Of Sight Range
N/A
N/A
Latency - Dongle
N/A
N/A
Recorded Latency
N/A
PC Compatibility
Analog
Audio Only
Audio Only
Wired USB
No
No
Non-BT Wireless
No
No
PlayStation Compatibility
PS4 Analog
Audio Only
Audio Only
PS4 Wired USB
No
No
PS4 Non-BT Wireless
No
No
PS5 Analog
Audio Only
Audio Only
PS5 Wired USB
No
No
PS5 Non-BT Wireless
No
No
Xbox Compatibility
Xbox One Analog
Audio Only
Audio Only
Xbox One Wired USB
No
No
Xbox One Non-BT Wireless
No
No
Xbox Series X|S Analog
Audio Only
Audio Only
Xbox Series X|S Wired USB
No
No
Xbox Series X|S Non-BT Wireless
No
No
Base/Dock
0.0
0.0
Type
No Base/Dock
No Base/Dock
USB Input
No
No
Line In
No
No
Line Out
No
No
Optical Input
No
No
RCA Input
No
No
Dock Charging
No
No
Power Supply
No Base/Dock
No Base/Dock
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Standard
HD 660 S
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Sundara 2020
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HD 660 S
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Sundara 2020
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HD 660 S
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Finding storeBlack
Sundara 2020
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Finding storeStandard
HD 660 S
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Sundara 2020
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HD 660 S
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Sundara 2020
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Sennheiser HD 660 S
HiFiMan Sundara 2020
Comments
Sennheiser HD 660 S vs HiFiMan Sundara 2020: Main Discussion
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