Sennheiser’s HD660S2 Headphones Offer a New Twist on a Classic

Sennheiser has been engineering high-end headphones for almost 75 years and whilst there has been a lot of recent changes, the German manufacturer is still considered to be one of the leading brands in the category.

There was some concern when Sonovo took over the consumer products division that the focus on audiophile products might become less important to the company with its relatively small market and high R&D costs — but so far Sonovo appears to have decided to refresh the audiophile categories with new IEMs, wireless headphones, and the brand new Sennheiser HD660S2 that were just introduced earlier this week.

This is a big deal because the HD660S was already a really good headphone with a significant following.

I have lost track of the number of times I’ve recommended the HD650 and HD660S over the years as they sit right in the sweet spot for price/performance and it’s hard to get something better without spending a lot more.  

This new model follows in the footsteps of its predecessors having been designed in Germany and it will be assembled in Ireland on the same production equipment used for the HD650 and HD660S.

Externally, the changes are minor with the HD660S2 retaining the same basic frame and color-ways as its predecessor with brass badging distinguishing it from the earlier versions.   

The cups are the same external dimension (although dramatically redesigned internally) and use the same connectors as other HD6x0 models; which means that all of the third party pads, cables, and accessories will work with the new HD660S2.

That’s good news for those who have invested in XLR cables or other high-cost accessories.    

The other good news is the HD660S2 ships with both a 6.35mm and a 4.4mm balanced cable so purchasers may not need aftermarket options.

The Skinny

“Our new Sennheiser HD 660S2 offers listeners what they requested most from the headphones’ predecessor,” says Jermo Koehnke, Sennheiser Audiophile Product Manager. “With precision and power like no other and new sensitivity across all frequencies, listeners will hear details they’ve never heard before, especially at the lower end of the spectrum.”

The Depth and Drama Audiophiles Crave

​Improving on a beloved classic while retaining its best traits was a challenging task, starting with the lowest end of the frequency plot. The HD 660S2’s warm bass characteristics pair perfectly with its silky-smooth treble performance and trademark vocal presence, allowing the timbre and uniqueness of any instrument part to stand out. 

Across the entire frequency spectrum, the HD 660S2 delivers a refined listening experience thanks to improved transducer airflow and a refined voice coil. From thunderous timpani crescendos to pulsating EDM rises, even the most discerning audiophiles will notice the depth and nuance of low-frequency passages, adding dramatic flair to any type of music.

Ultimately, listeners are treated to deeper, clearer bass without sacrificing the expansive detail the series is known for. By reducing the voice coil’s weight, impulse response improves, bringing hyper-realistic textures to the forefront of any performance reproduction.

The overall experience is smoother and warmer than the original HD 660S, thanks to ​ that reduces the distances between select peaks and troughs. The overall impedance matches that of the HD 600 and HD 650, at an audiophile-friendly 300 ohms, for punchy dynamics and impressively low distortion.

Fit

​Designed in Germany and manufactured at Sennheiser’s state-of-the-art Ireland production facility, the HD 660S2 continues the series’ emphasis on quality, functional design using materials that contribute to the hi-fi experience.

Plush earpads and cushy headband padding place the revised 300-ohm transducers at the optimal distance from the ear resulting in a spacious soundstage with an abundance of detail — even for extended musical exploration. The transducer surround drops the resonant frequency from 110 Hz (original HD 660S) down to 70 Hz for hefty kick drums that move with ease. Even the outer mesh grilles are crafted to manage airflow at the ideal impedance for exquisite open-back listening sessions. 

Versatile enough to connect to vintage classics and modern solutions alike, the HD 660S2 ships with two 1.8 meter (5.8 ft) user-detachable cables that terminate to 6.3 mm (1/4-inch) single-ended stereo and 4.4 mm balanced stereo jack plugs, respectively.

A 6.3 mm to 3.5 mm (1/8-inch) adapter is also included, for use with popular hi-fi gear from DAC-amps, DAPs, and dedicated amplifiers such as the Sennheiser HDV 820. Distinguishing bronze accents complement the elegant jet-black finish, all of which is protected by a storage pouch.

We have our request in now for a review pair and will be sure to post and in-depth review as quickly as we can get a pair in hand.  

Pricing & Availability

​The Sennheiser HD 660S2 are available now for $599.95 at Amazon and Crutchfield.