The present application provides a method of manufacturing a resonant panel (200) of a flat panel loudspeaker. The method comprises: pressing a resonant panel blank between a first pressing surface (302) and a second pressing surface of a press, whereby to form the resonant panel (200) of the flat panel loudspeaker. The second pressing surface substantially opposes the first pressing surface (302). The first pressing surface (302) comprises at least one tool relief region (306, 312, 314, 316, 318), whereby to form at least one corresponding respective panel relief region (206, 212, 214, 216, 218) in a surface of the resonant panel (200).