A loudspeaker has a loudspeaker driver and a first tube having a base end coupled to the driver and extending towards the rear end of the loudspeaker. A second tube of larger cross sectional dimensions extends over the first tube and loudspeaker driver and has a rear end wall spaced from the open rear end of the second tube and a front end coupled to the driver. A third, open ended tube of smaller cross-sectional dimensions than the first tube extends through a rear end wall of the second tube and into the first tube, with the front end of the third tube spaced from the base of the first tube. A folded, three segment transmission line is formed between the first and second tubes, between the second and third tubes, and through the third tube.