"Headphones" is plural. The "phone" bit refers to the actual drivers, of which there are at least two in a pair of stereo headphones. That's why we say a pair o

"Headphones" is plural. The "phone" bit refers to the actual drivers, of which there are at least two in a pair of stereo headphones. That's why we say a pair of headphones. AirPods Max are headphones.