Sound reinforcement quality in stadium bowls continues to improve, due to the continuously increasing skills of the audio/acoustical consultants designing these systems, in tandem with steadily advancing technology.

Dramatically improved sound quality is displayed in full force in the U.S., where no fewer than 10 new stadiums hosting National Football League (NFL) franchises have opened in the past three years alone, complete with state-of-the-art sound systems. Even long-established facilities, such as Giants Stadium in Meadowlands, NJ, and Rich Stadium in Buffalo, NY, have recently upgraded to newer, more dynamic audio systems.

While all modern professional football stadiums in the U.S. share roughly the same dimensions, structure and seating capacities (65,000 - 75,000), each is now afforded two primary choices when it comes to sound design. One is the classic “main cluster” approach, where sound coverage is supplied by a single grouping of loudspeakers in one of the end zones, usually residing with the scoreboard and at least one large video screen.

The other method is a distributed system, where hundreds of smaller loudspeakers are mounted throughout the seating area, with each loudspeaker assigned to cover only a specific, nearby area. (Occasionally there are hybrid designs combining both, usually a main cluster augmented by smaller loudspeakers covering severely shadowed regions.)

Why choose one approach over the other? For answers, we turned to representatives of Acoustic Dimensions, responsible for the sound design at the new Lincoln Financial Field in Philadelphia, PA, and the recent retrofit at Rich Stadium; and Wrightson, Johnson, Haddon & Williams (WHJW), sound designer for the new Gillette Stadium in Foxboro, MA, and the new Seahawks Stadium in Seattle, WA, along with identical duties at Heinz Field in Pittsburgh, PA, which opened a year ago.

Both firms are coincidently based in Dallas, TX, and they supply the overwhelming majority of stadium sound designs in the U.S. in addition to enjoying a deep well of international clientele as well.

The choice of approach lay largely with the client, according to all of these qualified sources, with the sound design team working to fully educate their customers on the “ins and outs” of each from the beginning of a project. Specifically, final selection most frequently comes down to the production values expected of the system, combined with the budgetary situation.

The main cluster approach is generally more economical than its counterpart, simply because it employs far fewer loudspeaker, amplifier and digital signal processing components as well as much less cabling, infrastructure and installation labor, explains Ron Baker, senior designer for WJHW, which implemented a main cluster of high-output full-range loudspeakers at Heinz Field.

Another positive of a single-point main cluster is that it gives you a sense of place - the sound’s coming from way over there, so you definitely get the feel that this is a huge stadium filled with people for a football game.

WJHW senior consultant Jack McCallum notes that there are very few single-point loudspeaker options available that can supply even and coherent full-bandwidth coverage at the tremendous distances and throughout the large overall area presented at a stadium like Heinz Field. From this select group he settled on an appropriate type of loudspeaker to form the single cluster that would reside on a custom platform mounted above the scoreboard and video screens.

Working with the architect, WJHW was able to have a steel thrust attached above the Heinz Field scoreboard to get the loudspeaker cluster ‘out and away’ from the structure, helping to form the appropriate cluster ‘arc’ needed for optimum performance. This also curtails potential shadowing effects created by a more standard platform.

The potential downside of a main cluster approach can be somewhat lower overall sound quality, due to the distance sound must travel before reaching the majority of listeners. Factors like humidity can significantly attenuate the higher frequencies, while thermal conditions and wind can cause sound to fade in and out, or to "swirl".