Before revision: Open- or closed-back Both circumaural and supra-aural headphones can be further differentiated by the type of earcups: Open-back Open-back headphones have the back of the earcups open.
After revision: Open- or closed-back Both circumaural and supra-aural headphones can be further differentiated by the type of earcups: Headphones having the back of the earcups open.