Sennheiser's HD 4. 20s closed-back over-ear headphones offer superb audio quality combined with a durable and compact folding design. Plush leatherette ear-pads ensure a comfortable listen, and an inline one-button remote and mic allows you to stay in control of your device and take calls on the go. Superb Sennheiser Sound The closed-back over-ear design creates a rich soundscape with precise acoustic response and dynamic bass. With a frequency response of 18-20000 Hz, audio is detailed, balanced, and lifelike, delivering renowned Sennheiser sound quality. Read more… Calls on the Go A convenient one-button smart remote on the tangle-free cable gives control over your device and lets you take hands-free calls when out and about. Durable, Comfortable Premium leatherette ear-pads ensure good attenuation of ambient noise and ensure a comfortable listen, even over long sessions. The HD4. 20s headphones are lightweight, sturdily designed for everyday use, and they can be folded for storage.