The Sennheiser HD 660S is an open-back, over-ear headphone that has gained popularity among audiophiles for its refined sound and exceptional comfort. It is the successor to the highly acclaimed HD 650 and builds upon its legacy with improved sound performance, better build quality, and enhanced versatility. Designed primarily for home listening, the HD 660S offers a natural, detailed, and immersive audio experience, making it ideal for those who appreciate high-fidelity sound.
1. Design and Build Quality
The Sennheiser HD 660S maintains the classic design of its predecessor, the HD 650, with a few subtle yet significant improvements. It features a sleek, matte-black finish with a modern and understated look. The headphones are made primarily of high-quality plastic, with metal components in the headband to provide extra durability and flexibility. The use of premium materials ensures that the HD 660S is lightweight and robust, suitable for extended listening sessions.
The earcups are generously cushioned with soft velour padding, which provides a plush and comfortable feel on the ears. The open-back design allows for ventilation, reducing the risk of heat buildup, which can be an issue with closed-back headphones. The headband is also well-padded and adjustable, ensuring a snug yet comfortable fit. Overall, the build quality is excellent, with a focus on long-lasting comfort and durability.
2. Sound Quality
The Sennheiser HD 660S is known for its superb sound quality, which is characterized by a natural, balanced, and detailed audio profile. These headphones use new and improved transducers that reduce harmonic distortion and provide a more refined sound signature compared to the HD 650. The result is a clearer, more dynamic, and engaging listening experience.
Bass: The HD 660S offers tight, accurate bass that is well-controlled and precise. While it doesn’t have an exaggerated bass response, it reproduces low frequencies with great detail and texture. The bass is punchy and well-defined, making it suitable for genres that require bass accuracy rather than overwhelming power.
Mids: The midrange is where the HD 660S truly shines. Vocals and instruments are clear, natural, and full-bodied, with a sense of warmth that enhances the listening experience. The mids are neither recessed nor overly forward, maintaining a balanced presentation that appeals to purists who seek an authentic sound.
Highs: The treble is smooth and detailed, without being harsh or sibilant. The HD 660S manages to deliver high frequencies with precision, allowing for excellent resolution and clarity. This makes the headphones ideal for genres that require nuanced sound reproduction, such as classical, jazz, and acoustic music.
The open-back design of the HD 660S contributes to a spacious and natural soundstage, which enhances the sense of depth and separation between instruments. This design choice allows for a more immersive listening experience, but it also means that sound leaks out of the headphones, and ambient noise can be heard during use. Therefore, these headphones are best used in quiet environments.
3. Connectivity and Compatibility
The Sennheiser HD 660S is designed for versatility and can be connected to a wide range of audio equipment. It comes with a detachable cable system, which allows users to switch between different cables depending on their setup. The package includes a 6.3mm standard cable, a balanced 4.4mm Pentaconn cable, and a 6.3mm to 3.5mm adapter, providing multiple connection options for various devices.
These headphones have an impedance of 150 ohms, which is lower than the 300-ohm impedance of the HD 650. This makes the HD 660S more compatible with a broader range of devices, including portable players, smartphones, and laptops. However, for the best sound quality, it is recommended to pair these headphones with a high-quality headphone amplifier or DAC (Digital-to-Analog Converter), which can unlock their full potential.
4. Comfort and Fit
Comfort is a crucial aspect of the HD 660S, especially considering that they are designed for long listening sessions. The headphones are lightweight (260 grams) and feature a comfortable fit that doesn’t exert excessive pressure on the head. The earcups are spacious and covered with breathable velour pads, which reduce fatigue and heat buildup.
The adjustable headband ensures a secure fit, and the overall clamping force is balanced to keep the headphones stable without causing discomfort. Users who wear these headphones for hours will appreciate the soft, pressure-free design that allows for extended periods of listening without feeling tight or cumbersome.
5. Specifications
- Type: Over-ear, open-back
- Transducer Technology: Dynamic
- Impedance: 150 ohms
- Frequency Response: 10 Hz – 41 kHz
- Sound Pressure Level (SPL): 104 dB at 1V
- Total Harmonic Distortion (THD): <0.04% at 1 kHz, 100 dB SPL
- Connectivity: Detachable cable (6.3mm, 4.4mm balanced, 3.5mm adapter)
- Weight: 260 grams
- Cable Length: 3 meters
- Accessories: Storage pouch, multiple cables (6.3mm, 4.4mm balanced, 6.3mm to 3.5mm adapter)
6. Pros and Cons
Pros:
- Exceptional sound quality with natural, balanced audio
- Comfortable and lightweight design for long listening sessions
- Versatile connectivity with multiple cable options
- Improved impedance for better compatibility with various devices
- Open-back design offers a spacious and immersive soundstage
Cons:
- Open-back design leaks sound and lets in external noise, limiting portability
- Requires a high-quality amplifier or DAC for optimal performance
- Premium price point may not appeal to casual listeners
Conclusion
The Sennheiser HD 660S is a premium headphone that is ideal for audiophiles seeking a natural, detailed, and immersive sound experience. With its refined audio quality, improved transducers, and versatile connectivity, it offers a significant upgrade from its predecessor while retaining the classic features that made the HD 650 so popular. The open-back design ensures a spacious soundstage, making it perfect for home listening and studio use.
While the HD 660S is not designed for on-the-go use due to its open-back nature, it excels in providing an authentic and high-fidelity listening experience in quiet environments. Users who appreciate nuanced sound reproduction and comfort will find the HD 660S to be a worthy investment, especially when paired with a quality amplifier or DAC. Whether you are a fan of classical, jazz, rock, or acoustic music, the HD 660S delivers a balanced, detailed, and enjoyable audio experience that stands out in its class.