Sennheiser HD 660 S2 – Over Ear Open Back Wired Headphones

Sennheiser HD 660 S2 Headphones

The HD 660S2 is an open-back, over-ear audiophile headphone featuring a revised 38 mm dynamic transducer with a uniquely powerful vented magnet system and an ultra-light aluminum voice coil. The 300-ohm impedance matches the legendary HD 600 and HD 650, while a more compliant surround drops the resonant frequency to 70 Hz, doubling the sound pressure at the very lowest frequencies for extended sub bass with extraordinary precision. Designed in Germany and made in Ireland, the HD 660S2 includes both a 6.3 mm unbalanced cable and a 4.4 mm balanced cable.

• Open-back, over-ear audiophile headphone
• 38 mm dynamic transducer with vented magnet system and ultra-light aluminum voice coil
• 300 Ω impedance
• Frequency response: 8 – 41,500 Hz (–10 dB)
• Sound pressure level: 104 dB (1 kHz, 1 Vrms)
• THD: ≤ 0.04% (1 kHz, 100 dB)
• Extended sub bass with resonant frequency lowered to 70 Hz
• Diffuse field equalized frequency characteristic
• Includes 6.3 mm unbalanced and 4.4 mm balanced OFC cables (1.8 m each)
• Weight: approx. 260 g (without cable)
• Designed in Germany, made in Ireland
• 2 Year Warranty

Highlights & Key Technologies

Revised Transducer with Extended Sub Bass
The HD 660S2 features a revised 38 mm dynamic transducer with a uniquely powerful vented magnet system. The ultra-light aluminum voice coil now matches the 300-ohm impedance of the legendary HD 600 and HD 650, providing higher magnetic force and electrical dampening for cleaner impulse response. The surround is more compliant than its predecessor, dropping the resonant frequency to 70 Hz. Considerable effort went into optimizing the airflow around the transducer, resulting in more sensitivity over the entire frequency spectrum because the magnet’s air gap works more efficiently. These measures result in even greater precision, speed, and resolution — with double the sound pressure at the lowest frequencies. Extension on the low end creates more space for the sound: against a deeper backdrop, highs feel more brilliant, the soundstage deeper, and emotions stronger.

Sound Signature
The HD 660S2 delivers an intimate, relaxed sound signature that combines outstanding precision with a natural, warm character. The diffuse field equalized frequency characteristic reproduces instruments and vocalists with breathtaking resolution. The frequency response extends from 8 Hz to 41,500 Hz (–10 dB), and the total harmonic distortion is no greater than 0.04% at 1 kHz and 100 dB. As far back as the HD 580, high-end Sennheiser headphones have inspired generations with balanced, natural reproduction. The HD 600, HD 650, and HD 660S all share visible and audible DNA with the HD 660S2.

Comfort & Design
The velour earpads provide a tactile comfort with just the right amount of tension for proper acoustic positioning. As an open-back design, the HD 660S2 gives your ears an extremely comfortable climate, even for extended listening sessions. The low total weight of approximately 260 g and the ergonomic headband rule out any potential discomfort. The contact pressure is approximately 6.0 N ± 1.0 N.

Cables & Connectivity
The HD 660S2 ships with two oxygen-free copper (OFC) cables, each 1.8 m in length: a 6.3 mm (1/4") gold-plated unbalanced stereo jack plug (3-pin), and a 4.4 mm balanced plug (5-pin). A 6.3 mm to 3.5 mm stereo jack adapter is also included. An optional XLR-4 balanced cable is available separately. The detachable cable design allows easy replacement.

Details & Specifications

MODEL INFORMATION
Model: HD 660S2
Article number (SKU): 700240

AUDIO PERFORMANCE
Transducer principle: Dynamic, open
Transducer size: 38 mm
Frequency response: 8 – 41,500 Hz (–10 dB)
Frequency characteristic: Diffuse field equalized
Nominal impedance: 300 Ω
Sound pressure level: 104 dB at 1 kHz, 1 Vrms
Total harmonic distortion (THD): ≤ 0.04% (1 kHz, 100 dB)
Long-term input power: Max. 500 mW (per EN 60-268-7)
Maximum value of the static magnetic field at the surface: 4.5 mT

PHYSICAL SPECIFICATIONS
Ear coupling: Circum-aural, open
Contact pressure: Approx. 6.0 N ± 1.0 N
Weight: Approx. 260 g (without cable)
Country of origin: Ireland

CABLE & CONNECTORS
Cable: Oxygen-free copper (OFC), 1.8 m
6.3 mm (1/4") stereo jack plug: Gold-plated, unbalanced, 3-pin
4.4 mm stereo plug: Balanced, 5-pin
Adapter: 6.3 mm (1/4") to 3.5 mm stereo jack adapter (unbalanced)

ENVIRONMENTAL
Operating temperature: –10°C to +55°C

INCLUDED ACCESSORIES
HD 660S2 open, dynamic headphones
6.3 mm (1/4") unbalanced OFC cable, 1.8 m
4.4 mm balanced OFC cable, 1.8 m
6.3 mm to 3.5 mm stereo jack adapter
Storage bag
User information