The HD201 are closed, dynamic headphones featuring extended, accurate response, impressive dynamic potential & remarkable comfort. The HD201 has an "over-the-ear, " closed-back design that delivers outstanding attenuation of ambient noise, encouraging the wearer to become fully immersed in sound without undue distractions. This headphone features exceptionally smooth, natural, extended response. The HD201s low frequency extends to 21 Hz & the HD215 to an amazing 12 Hz while both models perform to the upper limits of human hearing with ratings of 18k Hz & 22k Hz & deliver dynamic potential to spare for reproducing any musical style with real-world levels & impact, with SPL limits of 108d B & 112d B. So despite its unusually lightweight, comfortable design, the HD201stands ready to create a true "high-end" personal listening experience, with the natural tonalities & impressive dynamic impact experienced listeners expect from any headphone carrying the Sennheiser name. & of course, the HD201 carry Sennheisers two-year warranty.