Sennheiser Refurbished Excellent HD 660S2 Wired Over-the-Ear Review

The refurbished Sennheiser HD 660S2 are wired, open-back audiophile headphones. They offer detailed, natural sound but require a headphone amp and have no wireless features. They can be a great value if found around $400, but are only for serious listening at home.

If you're hunting for wired audiophile headphones, the Sennheiser HD 660S2 is a classic choice. These are open-back, wired cans, so they're built for serious listening at home or in the studio, not for blocking out the world on a commute. They have a 300-ohm impedance, which means they need a decent headphone amp to really shine, and they're designed to deliver a natural, relaxed sound with a bit of extra sub-bass compared to their famous predecessors. The price is a bit of a wild card here, as we're looking at a refurbished model, and our database shows prices ranging from a reasonable $400 to an absolutely insane $88,965 from some vendors. For most people, the question is whether a refurbished high-end Sennheiser is a smart way to get into serious audio.

Let's talk about sound. According to our data, the HD 660S2's audio performance sits in the middle of the pack compared to all headphones we track. That's a bit misleading, because these aren't trying to compete with Bluetooth ANC headphones. They're aiming for a specific, high-fidelity experience. The 300-ohm drivers and lightweight aluminum voice coils are designed for excellent impulse response and timbre, which translates to a detailed, intimate listening session. They're not the loudest or bassiest headphones out there, but for critical listening of music, they offer a solid and accurate performance. The 'studio' score in our database is their strongest suit, which makes sense.

The value proposition here is entirely about the price you find. At around $400 for a refurbished 'Excellent' condition model, these could be a fantastic deal for an entry into the Sennheiser 600-series lineage. But if you see them listed for thousands, run away. For a similar price, you could get brand-new, well-regarded wired headphones like the HiFiMan Sundara or even save up for a different Sennheiser model. The refurbished route is a gamble, but if Best Buy or another reputable seller has them at the low end of that range, it's worth considering.

This is a wired headphone in a wireless world, so the comparisons are interesting. Against wireless giants like the Sony WH-1000XM6 or Apple AirPods Max, the HD 660S2 loses on convenience, ANC, and battery life completely, but wins on pure, unadulterated sound quality for stationary listening. Against other wired audiophile options, it's a classic. It's often compared to its siblings, the HD 600 and HD 650, with the S2 version offering that bit more bass. The Sennheiser ACCENTUM Plus is a wireless option from the same brand, but targets a completely different, more casual user. The Bowers & Wilkins Px8 S2 is a luxury wireless option; if you care about materials and design more than pure wired fidelity, that's the path.

Skip these if you need headphones for commuting, travel, or the office. The open-back design leaks all your music and lets all the noise in, and there's no noise cancellation. Also, avoid them if you need a microphone for calls or gaming, as the mic performance is one of the worst we've seen. And if you want wireless convenience, look at the Sony WH-1000XM6 or Sennheiser's own ACCENTUM Plus instead. These are strictly for stationary, critical listening.

Should you buy the refurbished Sennheiser HD 660S2? Only if you're an audiophile looking for a wired, open-back headphone for home use, and you find it at a price near $400. You'll need a headphone amplifier, and you must accept zero wireless features. For that specific person, this could be a smart purchase. For anyone else, especially someone who wants headphones for commuting, work calls, or gaming, these are not the right choice. The wired nature and lack of a mic make them a specialist tool.