One of the things I enjoy about working in a venue for an extended period is the opportunity to become very familiar with the ins and outs of the system and the room. This allows me to better help touring artists achieve a quality sound, and it also means that I have an intimate knowledge of the shortcomings of the system.
Although I’d already worked on this venue’s main arrays to bring both level and spectral variance to within a few dB throughout the coverage area, the system is a typical example of the all-too-common reality of budget constraints. The mains cover about 90 percent of seats very well (I counted), but the first few rows of the orchestra-level seating are outside the coverage pattern, causing intelligibility issues for reinforced speech events.
Plans are in the works to augment the installed system with flown fill loudspeakers, but several upcoming events meant that I needed a (literal) stopgap solution. I placed two of the venue’s JBL PRX Series loudspeakers in the only practical position – the outer corners of the orchestra pit – and set about the tuning process. The approach for integrating front fills boils down to five simple steps:
1) Determine the extent of the existing coverage gap
2) Place and aim a loudspeaker to fill the gap
3) Set EQ
4) Set level
5) Set delay
The reality is that for some events there is simply no opportunity to set up an analyzer and do a “real” optimization on the fill systems. Since I believe that ears are the system tech’s most valuable tool, I decided that it would be fun and educational to try to determine the proper level, EQ, and delay values by ear, and then check them with the analyzer to see how close I came.
Coverage Gap: By walking the seating rows while playing my reference music, I was able to pace off the seats that needed the most help from the front fills. Tip: To make the high-frequency rolloff even more audible, try using pink noise. Figure 1 shows the house left seating area and the placement of the fill, with the affected seats shaded yellow.
Placement and Aim: Due to cosmetics and sightlines, the pit corners were the only placement option for the fill loudspeakers. I aimed them though what I judged to be the middle of the coverage area. Although common practice usually dictates aiming a loudspeaker’s on-axis point at the farthest seat, this doesn’t apply to front fills, because the closer seats need the most help, and the front fill gradually hands coverage off to the main system as we move further back.
EQ: I adjusted the parametric EQ on the console matrix driving the front fills while listening to my reference track. The general trend for front fills is going to be cutting back the HF, because of the smaller HF drivers placed much closer to the listener.
Level: With both the mains and the fills playing, I adjusted the fill until the fill area seemed to match the level of the mains.
Delay: By standing in the row where the mains and fills seemed to meet at equal level, I visually estimated that the front fills were about 11 feet (10 milliseconds) closer than the mains, so I added the 10 ms of delay to the matrix output at the console.