Imagine a lapel mic worn by a soft-spoken person trying to speak to a stadium full of people.
Being able to energize loudspeakers physically removed from the proximity of the microphone versus turning closer ones up louder will provide much more headroom before feedback.
When a symphony plays a quiet passage the main arrays are quiet.. and the delay positions are quiet. When the score gets much louder, the same dynamic happens.
If you were trying to achieve this intimacy at the back of the room without the delay loudspeakers, the long-throw portions of the rig would have to be turned up very loud relative to the rest of it.
Even though they may not be aiming directly at you, I believe you can still hear the extra energy from these devices filling the room, as it struggles to deliver clarity to the farthest audience members during the quiet passages, and perhaps running out of headroom during the louder ones.
By utilizing delay loudspeakers you can keep the system’s output more uniform throughout the room. I would rather try to capture the nuance of the performance using this ‘old school’ technology and avoiding the non-linear set-up. To successfully focus audio energy in to the areas of the room where coverage from the tamed main arrays is inadequate, optimizing the drive settings for the delay loudspeakers is critical to achieve the best results.
The main premise is that delay loudspeakers should be heard, but not perceived. While the value for ‘delay’ is ultimately very important, it is not the only consideration. Achieving this transparency is done by balancing the frequency response, delay time, gain and coverage angles of the delay loudspeakers relative to the main arrays.
For example, the delay time might be extended by a small increment compared to the actual measured value for the distance to the main arrays. This is because with two sources we tend to localize sound to the one we hear first. In this case we prefer the main arrays at the stage. Next the gain should be adjusted so the level is as low as possible, while still being effective,
Again, we tend to localize sound to the louder of two sources, so make the mains louder by turning the delays down. Think “invisible” when you are making these adjustments.
The frequency response of the delay loudspeakers is also important as to how well they work.
The premise here is to use the delay loudspeakers to keep the sound at the listening position spectrally balanced. To determine the best response you must first go to the audience areas to be covered by the delay loudspeakers, At a moderate level, listen to the main system with the delays off.
You will find many times, that the spectral information reaching the far parts of the audience is not nearly as balanced as it is on the floor at the mix position.
There is also coloration from the room itself that will sometimes accentuate different frequencies, and the distance from the mains may diminish high mid and high frequencies.