Sennheiser HD 660S2

In this sennheiser hd 660s2 review, the Sennheiser HD 660S2 is a $499.00 open-back audiophile headphone that ranks #4 of 9 in our best audiophile headphones guide, where it earns the best-for-deep-bass label. It scored 4.5 stars from 785 Amazon ratings, and its 42 mm transducers plus an ultra-light aluminum voice coil push down to a 27.5 Hz piano low. That matters if you want a wide, airy open-back soundstage with real sub-bass weight instead of the leaner low end of the HD 600 series. Buyers who mainly want neutral monitoring should look at the cheaper HD 600 instead.

On the technical side, the 42 mm transducers handle the 45 to 60 Hz range of bass drums and kick drums without blurring the mids, which means acoustic bass, piano and electronic tracks keep their texture. Sennheiser rates the HD 660S2 for piano lows down to 27.5 Hz, so the deepest notes stay audible rather than fading into a hum. Meanwhile, breathable plush ear cushions and the open-back frame prevent fatigue over long sessions. The box includes a 6.3 mm cable, a 4.4 mm balanced cable, a 6.3 mm to 3.5 mm adapter and a carry pouch, so you can move between a desktop amp and a portable player. On top of that, the build is assembled in Germany and Ireland and covered by a 2 year manufacturer warranty.

At $499.00, the Sennheiser HD 660S2 sits above the cheaper HD 600 and HD 650, which rate slightly higher at 4.6 stars but deliver less low-end weight. By contrast, this model trades a little of that neutral flatness for deeper, controlled bass, so the gap only shows up on bass-heavy tracks. In practice, the extra sub-bass is subtle unless you listen closely, and the 4.5 star score from 785 ratings reflects that. Skip it if you mainly monitor mixes or want the lowest price. However, if acoustic bass, piano and electronic music make up your library, this is the audiophile headphone to buy.