The Sennheiser HD 820 headphones have ring radiator transducers that are fitted using specialized glass covers. These glass covers not only show off the technical parts inside of the headphones, but they are designed with the purpose of enhancing the sound. Because the glass is concave, it reflects the sound waves from the back of the transducer up to the absorber. This helps minimize the resonance in the chamber and takes away the sound waves that are still present in open headphones. Exceptional levels of detail are given to each pair of these Sennheiser’s, ranging from everything like the handcrafted, ergonomic ear pads to stop ambient noise from getting in to the gold plate plugs and silver clad OFC cables and the ultra-durable metal headband with a dampening feature.