Sennheiser Hd 660S2 Open Over-Ear Headphones with Optimized Surround & Improved

The Sennheiser HD 660S2 is an open‑back, audiophile-grade upgrade to the revered HD 660S, built around enhanced 38 mm/42 mm dynamic drivers with a redesigned 300 Ω voice coil, compliant surround (dropping resonance from ~110 Hz to 70 Hz), and optimized airflow—all combining to deliver cleaner impulse response, deeper sub‑bass extension, smoother treble, and greater resolution across the spectrum. Reviewers highlight its “natural, warm, detailed” sonic signature with notably improved low-end presence compared to its predecessor , and Head‑Fi notes its robust build and comfortable, non‑fatiguing presentation