An acoustic waveguide for shaping waves comprising: walls (44; 66) defining a chamber having an input end and an output end with the chamber defined therebetween; an opening at the input end for receiving sound waves from an acoustic transducer; an opening at the output end for outputting sound waves; the chamber opening in a first direction from the input end to the output end, the first direction being transverse to a path from the input end to the output end, the chamber defining a first inner face (44; 66) and a second inner face (44; 66) opposing and facing the first inner face (44; 66); a plurality of projections (50; 76) provided on the first inner face (44; 66) and projecting outwardly therefrom, wherein the projections (50; 75) have a cylindrical shape or an elliptical shape; at least two vanes (46; 68, 70, 72) disposed on the first inner face (44; 66) of the chamber, the vanes (46; 68, 70, 72) extending from adjacent the opening at the input end and generally toward the output end; at least two vanes (46; 68, 70, 72) disposed on the second inner face (44; 66) of the chamber, the vanes (46; 68, 70, 72) on the second inner face (44; 66) of the chamber being in alignment with the vanes (46; 68, 70, 72) on the first face of the chamber; a plurality of projections (50; 76) provided on the second inner face (44; 66) of the chamber and projecting outwardly therefrom, the projections (50; 76) on the second inner face (44; 66) being in alignment with the projections (50; 76) on the first inner face (44; 66); two waveguide members (32, 34) that are mirror images of each other, wherein the first inner face (44; 66) is associated with a first one of the waveguide members (32, 34) and the second inner face (44; 66) is associated with a second one of the waveguide members (32, 34); and a gasket provided between the first waveguide member and the second waveguide member, the gasket providing a seal between the vanes (46; 68, 70, 72) on the first inner face (44; 66) and the second inner face (44; 66), and the gasket providing a seal between the projections (50; 76) provided on the first inner face (44; 66) and the projections (50; 76) provided on the second inner face (44; 66). walls (44; 66) defining a chamber having an input end and an output end with the chamber defined therebetween; an opening at the input end for receiving sound waves from an acoustic transducer; an opening at the output end for outputting sound waves; the chamber opening in a first direction from the input end to the output end, the first direction being transverse to a path from the input end to the output end, the chamber defining a first inner face (44; 66) and a second inner face (44; 66) opposing and facing the first inner face (44; 66); a plurality of projections (50; 76) provided on the first inner face (44; 66) and projecting outwardly therefrom, wherein the projections (50; 75) have a cylindrical shape or an elliptical shape; at least two vanes (46; 68, 70, 72) disposed on the first inner face (44; 66) of the chamber, the vanes (46; 68, 70, 72) extending from adjacent the opening at the input end and generally toward the output end; at least two vanes (46; 68, 70, 72) disposed on the second inner face (44; 66) of the chamber, the vanes (46; 68, 70, 72) on the second inner face (44; 66) of the chamber being in alignment with the vanes (46; 68, 70, 72) on the first face of the chamber; a plurality of projections (50; 76) provided on the second inner face (44; 66) of the chamber and projecting outwardly therefrom, the projections (50; 76) on the second inner face (44; 66) being in alignment with the projections (50; 76) on the first inner face (44; 66); two waveguide members (32, 34) that are mirror images of each other, wherein the first inner face (44; 66) is associated with a first one of the waveguide members (32, 34) and the second inner face (44; 66) is associated with a second one of the waveguide members (32, 34); and a gasket provided between the first waveguide member and the second waveguide member, the gasket providing a seal between the vanes (46; 68, 70, 72) on the first inner face (44; 66) and the second inner face (44; 66), and the gasket providing a seal between the projections (50; 76) provided on the first inner face (44; 66) and the projections (50; 76) provided on the second inner face (44; 66).