A wide beam angle (diffuse) luminaire with an efficient multi-source radiative emitter array. Embodiments of the luminaire utilize one or more LEDs disposed around a perimeter of a protective casing. The LEDs are angled to emit into an internal cavity defined by the inner surface of the casing. The placement of the LEDs around the perimeter of the device reduces self-blocking and facilitates heat transfer from the LEDs through the casing or another heat sink and into the ambient. Light impinges on the inner surface and is redirected as useful emission. A diffuse reflective coating may be deposited on the inner surface to mix the light before it is emitted.