Signals on respective RL, FL, C, FR, RR channels are divided into high frequency signals and low frequency signals by HPFs and LPFs respectively. The low frequency signals on the RL, FL, and C channels are superposed and output from a left-side woofer 21-1, while the low frequency signals on the RR, FR, and C channels are superposed and output from a right-side woofer 21-2. A predetermined directivity is given to the high frequency signals on respective channels by directivity controlling portions 17-1 to 17-5 respectively, and resultant signals are output from respective speaker units 20-1 to 20-n of an array speaker to generate virtual sound sources by the reflection from wall surfaces. A crossover frequency f2 of the rear channels (RL, RR) is set higher than a crossover frequency f1 of the front channels (FL, FR), and the signals on the rear channels are shaped into a narrow beam to generate a high-quality surround sound field.