An omnidirectional loudspeaker to provide uniform sound distribution in both a vertical plane and a horizontal plane, comprising: first and second axisymmetric reflectors (105a, 105b) sharing a common axis of symmetry, each reflector being in the form of a convex body having a curved surface (104a, 104b) that surrounds an end face, the two end faces (103a, 103b) facing each other and defining therebetween a straight section of a horn of the speaker, the straight section being defined by straight sides (103a, 103b) provided by the two end faces, the straight section extending inwards from an outer periphery (b) in the direction of the common axis, the curved surfaces (104a, 104b) extending from the outer peripheries of the straight section, to outer peripheries (c1, c2) of the curved surfaces (104a, 104b) and away from each other, so that the distance between them in the axial direction increases with increasing radial distance from the axis of symmetry, and defining therebetween a growth section of the horn leading to a horn exit at the outer peripheries (c1, c2) of the curved surfaces, one or both of the axisymmetric reflectors (105a, 105b) including an aperture in its end face and a sound source arranged to emit sound through the aperture and into the straight section of the horn, the or each sound source and aperture being at, and centred on, the axis of symmetry, the two curved surfaces being so shaped that, from the outer periphery (b) of the straight section to the outer peripheries (c1, c2) of the curved surfaces, the derivative of the axial distance between the curved surfaces with respect to the radial distance from the axis of symmetry is greater than 1, the arrangement being such that between the or each sound source and the horn exit, the sound emitted by the or each sound source is guided and reflected by the geometry of the first and second reflectors to provide the uniform sound distribution in both a vertical plane and a horizontal plane, wherein the axial distance between the first axisymmetric reflector and the second axisymmetric reflector varies based on the radial distance, r, from the axis of symmetry; and the axial distance grows as C/r ∗ exp(B ∗ r), wherein C and B denote constants based on one or more dimensions of a throat and a mouth of the horn. first and second axisymmetric reflectors (105a, 105b) sharing a common axis of symmetry, each reflector being in the form of a convex body having a curved surface (104a, 104b) that surrounds an end face, the two end faces (103a, 103b) facing each other and defining therebetween a straight section of a horn of the speaker, the straight section being defined by straight sides (103a, 103b) provided by the two end faces, the straight section extending inwards from an outer periphery (b) in the direction of the common axis, the curved surfaces (104a, 104b) extending from the outer peripheries of the straight section, to outer peripheries (c1, c2) of the curved surfaces (104a, 104b) and away from each other, so that the distance between them in the axial direction increases with increasing radial distance from the axis of symmetry, and defining therebetween a growth section of the horn leading to a horn exit at the outer peripheries (c1, c2) of the curved surfaces, one or both of the axisymmetric reflectors (105a, 105b) including an aperture in its end face and a sound source arranged to emit sound through the aperture and into the straight section of the horn, the or each sound source and aperture being at, and centred on, the axis of symmetry, the two curved surfaces being so shaped that, from the outer periphery (b) of the straight section to the outer peripheries (c1, c2) of the curved surfaces, the derivative of the axial distance between the curved surfaces with respect to the radial distance from the axis of symmetry is greater than 1, the arrangement being such that between the or each sound source and the horn exit, the sound emitted by the or each sound source is guided and reflected by the geometry of the first and second reflectors to provide the uniform sound distribution in both a vertical plane and a horizontal plane, wherein the axial distance between the first axisymmetric reflector and the second axisymmetric reflector varies based on the radial distance, r, from the axis of symmetry; and the axial distance grows as C/r ∗ exp(B ∗ r), wherein C and B denote constants based on one or more dimensions of a throat and a mouth of the horn.