3D sound field rendering under non-idealized loudspeaker arrangements Alois Sontacchi, Franz Zotter and Robert Höldrich 1) Abstract The approach to realise periphonic sound field reproduction based on spherical base solutions of the wave equation has already been well-known as Ambisonics and High Order Ambisonics (HOA), respectively (see [1]). By the aid of an N-dimensional orthogonal set of vectors any arbitrary source free sound field can be described. Reproduction is realized by projection of the encoded sound field on a regular loudspeaker distribution over a spherical surface. The used set of vectors exhibits a defined hierarchic with interesting symmetries. In the original scheme sound sources represented by plane waves (sources in far distance) can be encoded independent of the decoding process on the regular loudspeaker layout. Usually, in practice - in contrast to theory, 3D loudspeaker layouts are requested for the upper hemisphere. This restriction is caused by the geometry of many rooms. First of all that restriction bounds the reproduction of sound sources to the upper area. With a complete set of N-th order spherical harmonics in such discussed cases a regular design of a HOA decoder is impossible. Figure 1: Schema of the IEM-CUBE loudspeaker layout. Goal Within this case study we will show how the symmetries of the spherical harmonics can be used to obtain optimized decoding rules and to overcome insufficient irregular loudspeaker arrangements in regard of incompletely sampled spheres. Based on an existing loudspeaker arrangement (IEM-CUBE, see Fig.1) for the upper hemisphere we will highlight that a reduced set of the spherical harmonics can cope with these conditions.