If I had to choose, I’d say the Sennheiser HD 660S2 Audiophile Headphones are best for organic, acoustic music with a strong focus on the most important part of the human voice’s frequency range. Bon Iver and classic singer/songwriter music sounds absolutely spectacular to me on these for example, and, outside of the slightly (and I stress slightly here) underwhelming thump in the lower register, vocal-heavy pop and electronic music does too.

Where the Sennheiser HD 660S was good, it to me never was the headphone that could make me completely forget about the HD 600 and HD 650. That’s exactly what’s different with this new S2 update. This time I do feel that people in 10 years’ time will still be talking about the HD 660S2, just like they did with the HD 650 and HD 600. The original HD 660S did not get our recommended buy award, but I feel the sound quality has improved in every possible way here.

Yes, they're hideously expensive, and in the current climate, it doesn't really seem right to recommend a set of £500/$600 headphones for everyone to try. However, that high price means the HD 660S2s are really only meant for the most professional of users who can get the most out of them. They really are some of the best headphones money can buy if you're wanting a true-to-life, warm sound that's also immensely precise, making them a real treat for games and music alike. You'll just have to watch out for that tight fit and heavy clamping force, which will take some getting used to.

The Sennheisers have a charming smoothness to their sound, but their soft bass and lack of dynamic thrust hold them back.

This hobby should be about having a blast, about the fun times & positive vibes and while Sennheiser slightly derailed the train with the HD660S release, they got back on track with a wackier-sounding HD660S2. Undoubtedly, these are a joy to listen to and while I no longer have the original HD580, HD600, and HD650 by my side, these feel like a natural follow-up, an extension to that kind of sound, getting even smoother, warmer, wider frequency wise and considerably more technical sounding along the way.

The Sennheiser HD 660S2 is slightly bassier than its predecessor, but this isn't for bass-heads, and also not for those who need significant treble emphasis. It's not a good or bad thing, it's just a preference issue—but this fact should inform your buying decisions.

Warm, smooth, and beautifully refined sound signature. Reference-quality detail and dynamics. Deep, articulate bass response. Multiple cable options. Included 3.5-mm adapter.

The Sennheiser HD 660S2 are very good for neutral sound. They have a warm sound profile and, despite being open-back, pack more thump and rumble than their predecessor. Their exceptionally neutral mids also ensure that vocals and instruments sound natural and present. A dip in the low-treble hurts the clarity and detail of these sounds, while the following peak in the mid-treble makes sibilants sound more aggressive and piercing, comparatively. Their soundstage, which feels spacious and open, struggles to produce an out-of-head audio experience too, and you'll need an amp to power these over-ears. On the upside, they deliver bass and treble consistently across reseats.