A speaker system comprises a speaker transducer, a diffraction-slot acoustic waveguide and first and second mechanical acoustic barriers. The waveguide is arranged in proximity to the speaker transducer along a centerline of the speaker transducer so that the waveguide extends substantially an equal distance on both sides of the centerline of the speaker transducer. The area of the waveguide covers a corresponding area of the speaker transducer. The first and second mechanical acoustic barriers are respectively disposed on each side of the waveguide and cover the areas of the speaker transducer on both sides of the centerline of the speaker transducer that are not covered by the waveguide. The first and second mechanical acoustic barriers provide a low-pass filter for acoustic energy output from the speaker transducer.