Left-Right Arrays
For a stacked or flown left-right subwoofer system, using gradient arrays pointed offstage helps reduce lobing.
Figure 31 compares the coverage of a single-wide Xsub stack on either side of the stage with that of a gradient configuration of the same size.
Bass on Stage
Although Figure 31 doesn’t show it, the angled-hypercardioid configuration puts a good deal less bass onto the stage than the simple one.
For the simple configuration on the left, performers at center stage hear the summed output of both subbass stacks from a relatively short distance away. Nowhere in the venue is the subbass louder than this.
For the right-hand configuration, however, the gradient woofers’ hypercardioid nulls are pointed directly across the front of the stage. In typical configurations, this reduces the subbass level at downstage center by 15dB or more.
Coverage Control for Smaller Arrays
For small venues with flat floors, stacked subwoofers usually create excessive bass levels in the audience areas near the stage. While this might be fine for a dance club, it is not fine for a corporate AV presentation. In such cases, using a small center-flown subwoofer can provide excellent coverage without excessive levels anywhere.
However, if a conventional woofer is used, it will be essentially omnidirectional, which means that (a) large amounts of bass energy will be radiated into the reverberant field, which will make for muddy sound, and (b) the bass on stage will be quite loud.
In contrast, hanging a cardioid or hypercardioid woofer above the stage will put the bass energy where it’s needed—in the audience—and keep it out of the reverberant field and away from the stage.
Figure 32 shows a 120° hypercardioid woofer. If you think of the diagram as a horizontal polar plot, you’ll see that it puts most of the bass energy out front and not into useless directions. If you think of it as a vertical plot, you’ll see that the hypercardioid null points at the stage.
