Bass reflex Helmholtz resonator loudspeaker enclosure - has a low frequency cut=off adjustable by packing the enclosure vent with foam, e.g. polyurethane

摘要

The bass reflex loudspeaker cabinet encloses a loudspeaker and has a vent backed by an open cylindrical tube, the cabinet being a Helmholtz resonator. The vent enhances low frequency signals emitted by the loudspeaker and lowers the resonance frequency of the cabinet. The resonance frequency is to suit surrounding conditions by introducing foam packing, e.g. of polyurethane, into the tube to damp the sound output from the vent. The density, thickness, number of open and closed pores in the foam determine its damping effect. Several plugs of foam of differing parameters may be used together.