23rd International AES Conference
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Semi-classical Approximation of Loudspeaker Positioning in Room
Jean-Dominique Polack 1 and Jan Abildgaard Pedersen 2
1 Laboratoire d’Acoustique Musicale, Paris, France
2 Bang & Olufsen A/S, Struer, Denmark

The field radiated by a loudspeaker is sensitive to the loudspeaker placement, specially at low frequencies, because the room exerts an acoustical load on the membrane. One of the authors has based on it a compensation system called ABC. The paper focuses on the simulation of the acoustical load seen by the source. The method used is the semi-classical theory; that is, a variant of ray tracing that takes phases into account. It builds up the coherent part of the point transfer function - or acoustical load - for different source positions and the ratios give the compensation filters. The computed filters are compared to measurements obtained by the ABC system. The same overall shapes are obtained. Discrepancies subsist due to the finite size of the loudspeaker and phase shifts at the reflections on the walls not accounted for at present in the definition of absorption and reflection coefficients. So far, the simulation has been developed for rectangular rooms and point sources only.