Sennheiser HD 660S2: The Evolution of an Audiophile Legend

The Sennheiser HD 660S2 is the latest iteration of Sennheiser’s legendary 600 series, headphones that have been a reference for audiophiles for decades. This new version comes with significant improvements in bass response and a refined representation of sonic details.

Design and Comfort

Sennheiser has maintained the classic design of the 600 series, with an open-back structure that allows for more natural sound reproduction. The velour ear pads are extremely comfortable and allow for several hours of listening without fatigue. The headband distributes weight evenly, and at just 260 grams, they are surprisingly lightweight for headphones in this category.

The construction is robust, with quality materials that convey a sense of durability. The cables are detachable and come with 6.3mm and 3.5mm connectors, allowing them to be connected to both high-fidelity equipment and portable devices (although the latter are not their ideal environment).

Sound Quality

This is where the HD 660S2 truly shines. Sennheiser has refined the transducers to offer a richer and deeper bass response than the previous model, without compromising the clarity and neutrality that characterizes the 600 series.

The midrange is simply exceptional, with a representation of voices and instruments that is almost tangible. The treble is detailed and extensive, but never strident, offering a natural brightness that reveals subtle details in recordings.

The soundstage is wide and precise, with excellent instrumental separation that allows you to clearly distinguish each element in complex recordings. The dynamics are impressive, capturing both the most delicate moments and the most intense passages with equal precision.

Amplification Requirements

It’s worth noting that, with an impedance of 300 ohms, the HD 660S2 requires a good amplifier to show its full potential. In our tests, we’ve obtained excellent results with desktop amplifiers like the Schiit Magnius and the Topping A90, but they also work reasonably well with quality portable DAC/amplifiers.

However, don’t expect optimal performance by connecting them directly to a phone or laptop; these headphones deserve a quality audio chain.

Versatility and Musical Genres

The HD 660S2 are surprisingly versatile when it comes to musical genres. Their improved bass response makes them more suitable for electronic music and hip-hop than their predecessors, while maintaining excellence in classical music, jazz, and rock.

They are particularly impressive with acoustic and vocal recordings, where their ability to reproduce natural textures and nuances makes them shine. Voices sound incredibly realistic, with a presence that can give you chills.

Comparison with the Competition

Compared to other headphones in their price category, the HD 660S2 stand out for their neutrality and precision. The Focal Elex offers a more dynamic and impactful presentation, while the Hifiman Sundara has an even wider soundstage thanks to its planar magnetic technology.

However, the HD 660S2 offers an exceptional balance between resolution, natural tonality, and comfort that few competitors can match. Additionally, their legendary durability and availability of replacement parts make them a long-term investment.

Final Verdict

The Sennheiser HD 660S2 represents a refined evolution of an already legendary series. They offer exceptional sound quality, with a balanced and natural presentation that reveals details in recordings that you may have never noticed before. Their superior comfort and robust construction make them ideal companions for long listening sessions.

The price is considerable, and they need a good amplifier to shine, but for audiophiles looking for a reference listening experience at home, the HD 660S2 is an investment that will provide years of auditory pleasure.

They are not headphones for everyone: their open-back design is not suitable for outdoor use or noisy environments, and they require quality complementary equipment. But for critical listening in a quiet environment, they represent one of the best values in the world of high-fidelity audio.

Score: 4.7/5

Pros:

• Exceptional sound quality with impressive detail
• Improved bass response compared to the previous model
• Extremely comfortable for long listening sessions
• Robust and durable construction
• Detachable and interchangeable cables

Cons:

• High price
• Require a good amplifier to reach their full potential
• Open-back design that doesn’t isolate from external noise
• Not suitable for mobile use or outdoors