Abstract: A compact audio reproduction system for two input signals includes at least four loudspeakers disposed at the vertices of a quadrilateral not more than two feet on any side and such that no two loudspeakers are located at a distance from one another which is less than one-fourth the greatest distance between any two loudspeakers. The two input signals are connected to alternate speakers such that no two loudspeakers at adjacent vertices of the quadrilateral produce the same signal such that a listener at an arbitrary location perceives a sound source larger than the quadrilateral and significant stereo image. The signals received by two loudspeakers located at adjacent vertices may receive signals which are equalized separately from the signals received by the other loudspeakers for the purpose of reducing comb filtering and improving the tolerance of the device to placement near walls and other obstructions.

Abstract: A dual purpose loudspeaker incorporating at least two audio signal inputs and at least one switch is adapted to receive and reproduce either a single audio signal input or two audio signal inputs according to the position of the switch. A switch slide mechanically linked to the switch is provided which blocks one of the audio signal inputs when the switch is in the single-channel position, thereby preventing erroneous connection to the blocked audio signal input.

Abstract: A port for a loudspeaker is disclosed which is sufficiently weather resistant for long term outdoor use and which prevents debris, insects and other vermin from entering the loudspeaker and which is compact and efficient.