Sennheiser HD 660S2 Review
By 8mm Audio Experts | Audiophile Open-Back Headphones Review
The Sennheiser HD 660S2 Open-Back Headphones continue the legacy of the iconic HD 6XX headphone series. For decades, this lineup has been trusted by audiophiles, recording engineers, and music enthusiasts for its natural sound reproduction and long-term listening comfort.
The HD 660S2 builds upon the HD 660S with improvements focused primarily on acoustic performance. With a redesigned 38mm dynamic driver, optimized airflow through a vented magnet system, and extended bass response, the HD 660S2 aims to provide a more complete listening experience while preserving the balanced sound signature that defines the 6XX family.
Sennheiser HD 660S2 Specifications
- Type: Open-back over-ear headphones
- Driver: 38mm dynamic transducer
- Frequency response: 8Hz – 41,500Hz
- Impedance: 300 ohms
- Sensitivity: 104dB
- Total harmonic distortion: <0.04%
- Weight: Approximately 260g (without cable)
- Cables included: 4.4mm balanced cable and 6.35mm cable
- Ear pads: Plush velour
- Design: Open-back architecture
- Manufactured in Ireland
Sound Quality
The HD 660S2 is tuned to deliver a balanced and natural sound signature suitable for extended listening sessions.
Bass Performance
Compared with previous models in the HD 6XX series, the HD 660S2 offers noticeably improved sub-bass extension. Low frequencies reach deeper into the sub-bass region while maintaining tight control and clarity.
Midrange
The midrange remains the defining strength of the HD 660S2. Vocals, guitars, and acoustic instruments are reproduced with exceptional realism, making the headphones particularly well suited for classical, jazz, and vocal-focused music.
Treble
Treble extension is slightly more open and detailed than earlier models. This additional clarity improves perceived air and detail without introducing harshness during long listening sessions.
Driver and Acoustic Design
The HD 660S2 uses a redesigned 38mm dynamic driver developed by Sennheiser at its manufacturing facility in Ireland.
Key engineering improvements include:
- Vented magnet system for improved airflow
- Optimized diaphragm movement for lower distortion
- Aluminium voice coil tuned for 300-ohm impedance
- Improved driver compliance for deeper bass response
These refinements help deliver more controlled low frequencies and improved dynamic response compared with earlier models.
Design and Comfort
The HD 660S2 retains the familiar design language of the HD 6XX series. The lightweight construction and breathable velour ear pads make it comfortable for long listening sessions.
- Lightweight 260g design
- Soft velour ear cushions
- Open-back grille for natural soundstage
- Durable dual-entry cable system
The open-back design allows air and sound to move freely through the ear cups, creating a spacious listening experience similar to traditional loudspeakers.
Amplifier Requirements
With a 300-ohm impedance rating, the HD 660S2 benefits from being paired with a dedicated headphone amplifier. While basic devices may power the headphones, a proper amplifier helps deliver improved dynamic range and bass control.
Common pairing options include desktop DAC/amp units and dedicated headphone amplifiers designed for high-impedance headphones.
Best Use Cases
The HD 660S2 is designed primarily for quiet indoor listening environments.
Typical use cases include:
- Home hi-fi listening
- Studio reference monitoring
- Classical and jazz music listening
- Audiophile music setups
Because of its open-back design, the HD 660S2 does not isolate external noise and is not intended for commuting or office environments.
Pros and Cons
Pros
- Balanced and natural sound signature
- Improved sub-bass extension compared with previous models
- Excellent midrange clarity
- Wide and natural soundstage
- Comfortable lightweight design
Cons
- Requires a dedicated amplifier for optimal performance
- Open-back design leaks sound
- Not suitable for noisy environments
Final Verdict
The Sennheiser HD 660S2 represents one of the most refined iterations of the HD 6XX headphone series. With improved bass extension, balanced tonal accuracy, and exceptional comfort, it remains an excellent choice for dedicated home listening.
For listeners who want an open-back headphone with natural sound reproduction and long-session comfort, the HD 660S2 continues the tradition of Sennheiser’s reference-grade audio design.
a perfect summary for any audiophile considering the HD 660S2! You’ve captured the essence of what makes this headphone special without getting lost in unnecessary marketing fluff. As an Electrical Engineering student at Telkom University Surabaya, thank you for the detailed engineering context—this is a great reference for our signal processing and audio systems studies https://bee-sby.telkomuniversity.ac.id/