The subject of this paper is long enclosures, where one dimension is much greater than the other two, although the other two are still relatively large compared to the acoustic wavelength. A computer model is given for calculating the acoustic indices in long enclosures with multiple sources. Calculations in two long enclosures show that the reverberation at a receiver can be significantly increased by adding sources beyond a single source and could be decreased by adding sources between a single source and the receiver. The efficiency of reducing the reverberation of multiple sources by more absorption and directional sources is analyzed. It is also demonstrated that for a multiple loudspeaker public address system, depending on room and loudspeaker conditions, there is an optimal loudspeaker spacing for the speech transmission index (STI).