High performance sound systems are rapidly becoming the norm at collegiate sports facilities around the country. In keeping with this trend, the University of Oregon Athletic Department decided it was time to replace the existing sound system in its football stadium.

The existing system was made up of small format horns and four 12-inch low frequency drivers mounted in a structure above and behind the nearest seats. The entire system was powered by two amplifiers, each rated at 200 watts per channel into eight ohms. During football games, the closest listeners received a good dose of announcer from the system while far end zone spectators were unable to hear anything.

When AD began to design the system, the basic configuration became obvious. The open “bowl” shape of the stadium, available speaker mounting locations and cost limitations of the system were the main deciding factors. The design criteria was to provide full range sound for the entire stadium to a level of 100 dB (A) at 400 ft.

To achieve this, the cluster was mounted to a position atop the stadium club building. Even with the cluster mounted over 45 feet above the closest seating area, it was still a challenge to get the sound out to the far end zone without blasting spectators in the seats below and maintain consistent tonal response at all seats. We proceeded to perform computer modeling of a hybrid horn design to find what it would take to provide loud enough sound level to the far end zone without directing energy onto the seats below the cluster.

A meeting between the top-ranked Washington Huskies and the Oregon Ducks—with a record crowd of 47,000 plus—provided the systems first real test. While standing behind the opposite end zone from the cluster (approximately 500 feet away), sound system levels of 97 dB (A) with peaks of 100 were measured. System deviation was measured to be +/-3 dB (A) throughout the entire seating area.