A Sennheiser pop-up store in New York lets anyone test out its flagship $55,000 Orpheus HE-1, the most expensive headphones in the world. The headphone-and-amplifier setup can be tested out in a separate, soundproof room. The Orpheus is an electrostatic headphone, which differs from ordinary 'dynamic' headphones by how it replicates sound with as much tonal accuracy as theoretically possible.