Abstract: Port devices are provided which are mounted within bass-reflex speaker enclosures behind port openings therein. Each device has an outer mouth opening at the port opening of the speaker and an inner throat opening of smaller area, on the order of two-fifths that of the mouth opening. The devices are in forms including forms having cylindrical or polygonal tubular sections combined with planar inner end wall sections, a stepped form with an additional smaller inner tubular section, and forms with hemispherical and frusto-conical walls. The throat-mouth area ratios and the ratios of the volumes of the devices of those of the enclosures are such as to extend and increase low frequency response without producing booming effects.