A loudspeaker is disclosed in which a cone driver operates into one end of an acoustic channel having acoustically closed sides and an acoustically open front. A longitudinally extended member is mounted directly in front of, and in alignment with, the driver, so as to restrict the free space within the channel. The rear of the longitudinally extending member effectively extends within the voice coil former, such that the volume defined between the rear of the longitudinally extending member and the loudspeaker is an annulus. The profile of the longitudinally extending member differs in its vertical and horizontal planes so as to provide a lower acoustic impedance in one plane than in the other.