The Sennheiser HD 660S2 is an open-back audiophile headphone with 42mm transducers and a 300-ohm impedance, tuned natural and relaxed rather than hyped. It's built for quiet-room listeners who settle in for long sessions and will drive it from a desktop amp with enough voltage swing.
Who the Sennheiser HD 660S2 is for
Quiet-room home listening: The open-back design leaks sound in both directions, so it belongs in a quiet room rather than a shared or noisy space.
Long, low-fatigue sessions: The relaxed, un-hyped tuning is what makes long sessions possible when fatigue matters more than isolation.
Late evenings with a record: Unhurried evening listening at home is exactly the setting its open, relaxed presentation suits.
Desktop amp owners: At 300 ohms it needs a desktop amp with some voltage swing to be heard properly, so it fits a desk setup built around one.
Skip it if: you need isolation, or you won't add a desktop amp: the open-back design leaks sound both ways, and 300 ohms is a real drive requirement.
Sennheiser HD 660S2 key specs
Design: Open-back audiophile headphone
Driver: 42mm transducers
Impedance: 300 ohms
Sound signature: Natural, relaxed (not hyped)
Sound leakage: Leaks in both directions (open-back)
Recommended amplification: Desktop amp with some voltage swing
vs Sennheiser HD 650: Same open-back, 300-ohm, 42mm-driver formula, and it also wants a proper amp; pick the HD 650 for a natural, neutral voicing, or the HD 660S2 for relaxed, long-session tuning.
vs Fosi Audio I5: Uses a 97mm planar magnetic diaphragm at 28 Ω, versus the HD 660S2's 42mm transducers at 300 ohms; pick the I5 for HiFi monitoring work, the HD 660S2 for relaxed long sessions.
Yes. Every unit we sell is genuine and brand-new, shipped in its original packaging, and backed by our 1-year TonePier warranty and 45-day returns.
Where does my order ship from, and how long does it take?
Every order ships from our warehouse in China, with full tracking, and most orders ship within 3 business days. Shipping is free on every order; most US orders arrive within 7–15 business days and most orders to other countries within 7–20 business days — see our shipping policy for details.
What if it isn't for me?
You get 45 days to decide. Keep the packaging, keep it in like-new condition, and send it back for a refund. Ear tips unsealed for hygiene reasons are fine — we expect you to actually listen.
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