A loudspeaker includes a horn including a first end panel, a second end panel, a first side panel, and a second side panel. Edges of at least the first and second side panels define a diffraction slot opening. The first and second side panels are each fabricated from a sheet of flexible material held in a stressed, curved shape by at least a rigid support member. The panels are designed by an automated process based on a number of electro-acoustic transducers to be used in a loudspeaker, horizontal and vertical coverage angles for the loudspeaker, and a wall length for a horn of the loudspeaker.