Figure 18 shows the same array as in Figure 17, but with two additional XLC-215 woofers stacked on or in front of the stage.
The front-fill woofers are delayed by 2.0 mSec.
The shape of the curves is quite sensitive to the delay value. Performance is better, but not excellent.
Figure 19 shows how a bit of simple beamforming can give good results.
The bottom two boxes in the stack are delayed by 4 mSec. No other processing is applied.
In all of these scenarios, there is an overall bass level difference of 12-14dB from front to back. This will not be satisfactory for most applications. A perfect solution to the problem is difficult.
Where venue dimensions permit, high trim is the single most effective technique for evening out bass SPL from front to back.
In the preceding illustrations, trim height was 32 feet (~10m) to top of stack. Figure 20 shows the same beamformed array as in Figure 19, but with a trim height of 65 feet (~20m) to top of stack. The level shift from front to back is much less.