Fig. 10: Powerhouse alley with two subwoofers spaced 14 m (47 ft).
Figure 10 shows the alley for two single subwoofer boxes spaced 14 meters (47 feet). It is not as obvious graphically as it is audibly, but it can still be distinguished as an approximately 4 meter (13 feet) band with more intense color.
The only real way to avoid the powerhouse alley is to place all subwoofers in a single location. With smaller scale applications, placing all the subwoofers in the center is normally not a possibility, but the larger shows may benefit from flying subwoofers in the center.
It is important, however, to understand what is happening, so as not to blame the speakers. And being aware of the zones that get created before taking mixing decisions.
For instance, if the FOH console is located in the centre, we could chose a mix that is somewhat bass-heavy when listened to along the center line.
Off to the sides destructive interference will kick in and establish some frequency balance between the low frequencies and the rest of the system.