A loudspeaker system has at least a first electroacoustical transducer having a vibratable diaphragm for converting an input electrical signal into a corresponding acoustic output signal. An enclosure is divided into at least first, second and third subchambers by at least first and second dividing walls. The first dividing wall supports and coacts with the first electrical transducer to bound the first and second subchambers. At least a first passive radiator intercouples the first and third subchambers. At least a second passive radiator intercouples at least one of the second and third subchambers with the region outside the enclosure. Each passive radiator is characterized by acoustic mass. Each subchamber is characterized by acoustic compliance. The acoustic mass and acoustic compliances coact to establish at least three spaced frequencies in the passband of the loudspeaker system at which the deflection characteristic of the vibratable diaphragm as a function of frequency has a minimum.