Ideal and actual sampling layouts displayed as grey and black dots, respectively, with loudspeaker channel numbers. Angle definitions are based on a spherical head-related coordinate system. Azimuth angles increase counter-clockwise and are represented by φ ∈ [0°, 360°), and zenith angles are represented by ϑ ∈ [0°, 180°]. The solid and dashed grey horizontal lines show the loudspeaker rings and the horizontal plane at the listener's nominal ear height, respectively, with loudspeaker 35 indicating the default viewing direction.