A headphone comprising: two headphone earcups each comprising: an earcup housing defining an active chamber that acoustically couples a sound output side of a speaker to an ear of a user, and an inactive chamber that surrounds the active chamber; and a passive valve assembly configured to open in response to a positive pressure and a negative pressure within the active chamber to fluidly couple the active chamber to the inactive chamber and equalize a pressure between the active chamber and the inactive chamber.