An electroacoustic transducer of a horn loudspeaker emits sound, which is supplied through a sound conduit pipe to a horn and propagated out of the horn through a mouth of the horn. The sound conduit pipe is coupled to the horn via a rectangular opening in the upper one of the upper and lower walls forming the horn, to thereby provide a linear sound source for the loudspeaker. The location where the sound conduit pipe is coupled to the horn and/or the tilt angle of the sound conduit pipe with respect to the horn may be varied to control the sound radiation characteristic of the loudspeaker.