Sennheiser HD 660S2 Headphones

Dagobiet Morales Alfaro, Vanessa McCuaig, and Yannick Khong from RTINGS highlight the Sennheiser HD 660S2 as a thoughtfully tuned successor to the HD 660 S, delivering a flat and slightly warm sound signature with natural mids and a smooth treble that favors critical listening. They praise its consistent audio delivery, low harmonic distortion, and well-built, comfortable design, though note the high clamping force may cause discomfort for some users. The review emphasizes the headphones’ open-back design, which provides a spacious soundstage but results in poor noise isolation and significant audio leakage, making them unsuitable for travel, office, or sports use. The HD 660S2 require a powerful amplifier due to their increased impedance, and the lack of a microphone limits communication use. Unique insights include detailed measurements revealing stereo mismatch in the bass and a nuanced treble response that may not suit those seeking brighter cymbal detail. Overall, the review conveys a balanced, moderately positive tone, recommending the HD 660S2 primarily for dedicated, quiet listening environments.

What Hi-Fi? highlights the Sennheiser HD 660S2 as a refined and relaxed pair of audiophile headphones that excel in delivering a smooth, captivating midrange, especially for vocal and acoustic music lovers. Praising their comfortable design and lightweight build, the review emphasizes the headphones’ effortless, undemanding listening experience and detailed, intimate vocal reproduction. However, the HD 660S2 show clear limitations in bass performance, with soft, less dynamic low frequencies that lack the punch and tightness found in some rivals like the Beyerdynamic Amiron. This shortfall in bass impact and detail prevents the headphones from reaching their full potential, particularly on bass-heavy or more demanding tracks. Overall, the review conveys a measured enthusiasm, appreciating the HD 660S2’s strengths in midrange clarity and comfort while candidly noting that their subdued bass and limited dynamic drive hold them back from being truly exceptional.

Christian Thomas from SoundGuys highlights the Sennheiser HD 660S2 as a refined update to the HD 600 line, offering a slightly bassier and more “relaxed” sound profile that may appeal to listeners who prefer less treble emphasis. While the headphones deliver solid, competent audio performance with good imaging and comfort for extended listening sessions, the reviewer notes that the tonal changes are subtle and may not justify upgrading from previous models like the HD 660S or HD 650. The open-back design provides a natural soundstage but sacrifices noise isolation and causes sound leakage, making them best suited for quiet environments. Connectivity is straightforward but includes some inconvenient cable design choices. Priced near $600, the HD 660S2 is positioned as a niche product for enthusiasts who appreciate its sound signature, though the reviewer suggests waiting for a price drop or considering alternatives if budget or a brighter sound is a priority. Overall, the review is measured and encourages personal listening before purchase.

Henry St Leger from TechRadar highlights the Sennheiser HD 660S2 headphones as an excellent entry point into open-backed audio, praising their neutral, inoffensive sound signature and improved bass response over the previous model. He emphasizes their suitability for professional use, such as sound mixing and mastering, as well as for relaxed, high-quality home listening. The review notes the headphones’ comfortable fit, plush cushioning, and rigid build that minimizes vibration, though their weight feels slightly heavier than expected. While the open-back design offers an expansive soundstage and detailed audio reproduction, it limits portability due to minimal sound isolation and lack of wireless features like Bluetooth or ANC. St Leger also points out the need for high-impedance compatible devices or amplifiers to fully appreciate their performance. Overall, the HD 660S2s deliver a refined, balanced listening experience ideal for audiophiles and professionals, though they are less suited for casual or on-the-go use.

Geoffrey Morrison from SoundStage! Solo highlights the Sennheiser HD 660S2 headphones as a compelling choice for listeners who appreciate a spacious, open soundstage paired with detailed, airy treble. He praises their lightweight design despite their bold, sizable appearance and notes the inclusion of versatile cables and adapters. Morrison emphasizes the headphones’ clarity and balanced sound, particularly excelling with vocals and acoustic instruments, while acknowledging a slightly treble-forward profile that may not suit bass enthusiasts. He finds them easy to drive with both high- and low-powered sources, making them versatile for different listening setups. Compared to competitors like the Beyerdynamic T5p and more feature-rich models such as the Momentum 4 and Sony WH-1000XM5, the HD 660S2s stand out for their natural, relaxed sound and critical listening appeal. While not perfect, Morrison’s enthusiasm grows with extended listening, recommending these headphones for those valuing clarity and openness over heavy bass or extra features.

Headfonics praises the Sennheiser HD 660S2 as a significant technical upgrade over its predecessor, the HD 660S, highlighting improved low-end extension, enhanced dynamics, and more satisfying imaging. The reviewer appreciates the fresh driver design featuring an ultra-light aluminum voice coil, which delivers better impulse response and a richer bass experience, making the headphones well-suited for tube amplifier enthusiasts. While the overall design remains familiar and comfortable, subtle refinements such as increased memory foam and improved lateral adjustment enhance the fit, though the close, ovoid earcup shape may not suit all users. The included cables are durable and thoughtfully designed, though their length may be cumbersome for some desktop setups. Packaging is noted as a downgrade from previous models, with a simpler box and less protective storage, offset by a soft drawstring pouch. Overall, the review conveys a balanced, moderately enthusiastic tone, emphasizing the HD 660S2’s strong value proposition at its current price point while acknowledging minor comfort and packaging trade-offs.

James Barber from TechHive highlights the Sennheiser HD 660S2 as a bold departure from the brand’s traditionally neutral tuning, delivering a more musical and immersive listening experience that will appeal to a broader audience. Praising its exceptional soundstage, especially for guitar-driven music, Barber notes the headphone’s comfortable fit and solid build, though he cautions that the open-back design limits use to quiet, solo environments. He acknowledges some trade-offs, such as a slight dip in upper mids that may affect acoustic or vocal-heavy genres and the proprietary cables that lack a satisfying connection click. The minimalist packaging and included accessories reflect a practical rather than luxury approach. While the price is on the higher side, Barber believes the HD 660S2’s unique tuning and engaging sound make it a standout in Sennheiser’s 6XX line, predicting it will gain appreciation over time despite initial controversy among audiophiles.

Richard Barclay from The EAR highlights the Sennheiser HD 660S2 as a thoughtful evolution of the iconic 600 series, delivering a warmer, smoother, and more forgiving sound signature that stands out distinctly from its predecessors. He praises its improved bass extension and airier treble, which enhance realism and reduce listening fatigue, especially for rock and metal fans who prefer less aggressive midrange presence. The HD660S2 retains the series’ renowned comfort and build quality, though some design changes like shorter cables and simpler packaging reflect cost-conscious choices. Barclay notes the headphone’s excellent scaling with high-end sources and the flexibility offered by EQ adjustments to tailor its laid-back tuning. While the more relaxed voicing may not suit those seeking the bolder character of the HD660S, the HD660S2 is celebrated as a refined, versatile option that balances resolution with a richer, more engaging listening experience, making it a welcome addition to Sennheiser’s legendary lineup.

Kazi Mahbub Mutakabbir assesses the Sennheiser HD 660S2 as a thoughtful evolution of a beloved classic, delivering notable improvements—especially in bass extension and sub-bass clarity—while maintaining the series’ signature mid-centric sound. The review conveys a measured enthusiasm, praising the headphones’ comfort, build longevity, and balanced tuning that suits a wide range of genres. Unique insights include the upgraded vented magnet system and dual-entry cable design, which enhance durability and sound precision. However, the reviewer expresses reservations about the relatively modest advancements over the HD 650, particularly regarding soundstage width and bass slam, which fall short of expectations given the higher price point. The HD 660S2 excel as near-perfect studio monitors but may not justify their MSRP for all listeners. Overall, the tone is appreciative yet cautious, recommending the HD 660S2 especially if found at a discount, while acknowledging that the HD 650 remains a compelling alternative for vocal warmth and value.

Lieven from Headfonia provides a measured and informative assessment of the Sennheiser HD 660S2 headphones, highlighting their refined engineering and sound improvements over predecessors. The review conveys a respectful tone toward Sennheiser’s legacy, emphasizing the upgraded 38mm transducer with a 300-ohm impedance that enhances impulse response, low-frequency extension, and overall soundstage depth. While the reviewer notes the modest packaging as a minor drawback, they appreciate the comprehensive accessory set, including dual cables and adapters, which adds value. The article balances technical detail with practical observations, such as cable length and compatibility considerations. Enthusiasm is tempered but positive, reflecting confidence in the HD 660S2’s performance as a worthy successor and competitor in the high-end open-back headphone market. The review’s unique insight lies in its focus on the acoustic refinements and how these translate into a richer, more spacious listening experience, making it a solid choice for audiophiles seeking precision and emotional engagement.