The HD201 are closed, dynamic headphones featuring extended, accurate response, impressive dynamic potential and 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 HD201's low frequency extends to 21Hz and the HD215 to an amazing 12 Hz while both models perform to the upper limits of human hearing with ratings of 18kHz and 22kHz and deliver dynamic potential to spare for reproducing any musical style with real-world levels and impact, with SPL limits of 108dB and 112dB. So despite it's unusually lightweight, comfortable design, the HD201stands ready to create a true "high-end" personal listening experience, with the natural tonalities and impressive dynamic impact experienced listeners expect from any headphone carrying the Sennheiser name. And of course, the HD201 carry Sennheiser's two-year warranty.