In a bass-reflex sound reproducing system, a ducted port is utilized to reduce distortion in the lower portion of the frequency range. To increase relative sound pressure level in that lower portion, the enclosure is constructed to exhibit a predetermined acoustic compliance and is essentially air-tight except for a pair of primary openings. Mounted sealingly over one opening is the bass-range loudspeaker which exhibits a selected cone- suspension acoustic compliance, a given loaded free-air Q not less than 0.4, but not greater than 1.0 and a predetermined free-air resonant frequency. The ratio of the enclosure compliance to the cone compliance is no less than 0.707. The duct projects from around the periphery of the second opening and has its length and cross-sectional area such that it exhibits a tuned acoustic frequency the ratio of which to the speaker resonant frequency is not less than 0.5 and not greater than 1.0. Consequently, radiation through the duct is that of a frequency generally below that of the sound projected directly by the speaker, but is at a sound pressure level at least substantially equal to that of the sound projected directly by the speaker.
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