Although the Sennheiser HD 820 are a closed back headphone, they still preserve the immense, natural soundstage created by the original open back HD 800 S. This achievement is made possible by the unique concave glass that covers the transducers. It reflects the sound into an internal absorber that eliminates nearly all resonance within the headphones.

These headphones are not intended for public use with a cell phone. Sennheiser created the HD 820 for individuals to sit back at home and relax while the music carries them away. While they do not have active noise cancelling technology, the seal created around the ear and by the glass provides excellent isolation from ambient sounds. The light weight of the HD 820 allows for many hours of continuous enjoyment.