A headphone includes an acoustic transducer having a sound-radiating surface that moves along a first axis, a housing enclosing the acoustic transducer, a first acoustic chamber defined by a first side of the acoustic transducer and a first portion of the housing, the first acoustic chamber including a first reactive port in a serial configuration with an acoustic resistance to couple the first acoustic chamber with space outside the headphone, a second acoustic chamber defined by a second side of the acoustic transducer and a second portion of the housing, the second acoustic chamber separated from the first acoustic chamber by the acoustic transducer, and an opening coupling the second acoustic chamber to the wearer's ear canal along a second axis that is not parallel to the first axis.