Sennheiser HD 660S2 Open-Back Headphones

Step into a world of audiophile excellence with the Sennheiser HD 660S2, a modern refinement of the legendary HD 660S. Designed for discerning listeners, these open-back, over-ear headphones feature enhanced sub-bass response, matched drivers, and high-resolution transducers for a naturally balanced and emotionally powerful listening experience. With upgraded 300-ohm Duofol voice coils and a compliant surround tuned to 70 Hz, the HD 660S2 delivers double the sound pressure at 20 Hz compared to its predecessor — all while preserving pristine clarity and detail across the spectrum.

The open-back design promotes spacious soundstage reproduction, while ultra-soft velour ear cushions and an ergonomic headband provide lasting comfort. Crafted in Ireland with meticulous build quality, the HD 660S2 also comes with both 1/4" and 4.4mm balanced detachable cables, plus a 3.5mm adapter and carry pouch. It’s a powerful evolution in Sennheiser’s legacy of natural sound, offering unmatched clarity, imaging, and acoustic warmth for extended critical listening sessions.

Specifications

• Earpiece Design: Over-Ear (Circumaural), Open-Back
• Driver Type: 38mm Dynamic with Aluminum Diaphragm
• Voice Coil: Copper-Clad Aluminum Wire
• Impedance: 300 Ohms
• Frequency Response: 8 Hz – 41.5 kHz
• Resonant Frequency: 70 Hz
• Sensitivity: 104 dB SPL/V
• Matching Tolerance: ±1 dB
• Maximum SPL: 104 dB
• Total Harmonic Distortion (THD): 0.04%
• Audio Connectors: 1 x 1/4" TRS, 1 x 4.4 mm TRRRS (balanced)
• Included Adapter: 1/4" to 3.5 mm TRS
• Cable Type: Y-Type, Detachable, 1.8 m
• Earpiece Connector: 2 x 2-Pin Male
• Material: Aluminum, Steel, Plastic, Velour
• Weight: 260 g (9.2 oz)
• Packaging Dimensions: 10.7 x 7.5 x 4.1"
• Manufactured In: Ireland

Expanded Key Features List

• Enhanced Sub-Bass Extension: Double the sound pressure at 20 Hz delivers deeper, richer bass impact without losing detail.
• High-Resolution Transducer Design: 38mm drivers with aluminum diaphragms provide superior clarity and speed for audiophile listening.
• 300-Ohm Duofol Voice Coil: Optimized impedance matches high-end amps for cleaner impulse response and lower distortion.
• Open-Back Soundstage: Natural, spacious acoustic reproduction ideal for immersive, room-like listening experiences.
• Matched Driver Pairing: Minimal ±1 dB channel tolerance ensures balanced stereo imaging and tonal accuracy.
• Premium Comfort Design: Ultra-soft velour ear cushions and ergonomic headband deliver fatigue-free comfort over long sessions.
• Diverse Cable Options: Includes both 1/4" unbalanced and 4.4mm balanced cables, plus 3.5mm adapter and carry pouch.
• Crafted in Ireland: Built with precision materials and engineering in Sennheiser’s European manufacturing facility.

Q&A Section

Q: What’s the difference between the HD 660S and HD 660S2?
A: The HD 660S2 features improved sub-bass extension, optimized airflow, and 300-ohm Duofol voice coils for richer low-end and enhanced clarity.

Q: Are the HD 660S2 headphones suitable for portable use?
A: These are designed for stationary, high-fidelity listening with headphone amps and are not ideal for portable use due to the open-back design and 300-ohm impedance.

Q: Can I use the HD 660S2 with a smartphone or laptop?
A: While possible, the high impedance (300 ohms) requires a high-quality headphone amp to reach full performance potential.

Q: Do they support balanced audio?
A: Yes, the HD 660S2 includes a 4.4 mm balanced cable for use with balanced-output devices, enhancing dynamic range and reducing noise.

Q: Are the earpads replaceable?
A: Yes, the velour earpads are replaceable, allowing for long-term maintenance and comfort.

Q: How comfortable are the HD 660S2 for extended listening?
A: Extremely comfortable thanks to lightweight construction, velour ear cushions, and a pressure-optimized headband design.

Q: What accessories are included with the headphones?
A: The HD 660S2 comes with two detachable cables (1/4" and 4.4mm), a 3.5mm adapter, and a soft carrying pouch.

Q: Where are the HD 660S2 headphones made?
A: They are precision-engineered and manufactured in Ireland with high-quality components.