BILLINGS, MT – Pro Media/UltraSound recently installed a substantial EAW loudspeaker system at Rimrock Auto Arena within the MetraPark multi-facility events center here, including EAW AX Series speakers, SB Series large format subwoofers and CIS Series ceiling speakers. The project was part of a multimillion-dollar refit of the 12,000-seat arena, which was damaged by a tornado in June 2010.
According to Demetrius Palavos, senior sales and design engineer with Pro Media/UltraSound, the architecture of the arena had a significant impact on the design of the rigging and positioning of the new speaker system. Mark Graham of AV systems design consultants Wrightson, Johnson, Haddon & Williams, Inc. (WJHW) of Dallas, Texas, was the lead consultant on the project.
"Due to large roof trusses that run down each side of the building through the main seating, it required a different approach to the overall design of the loudspeaker system," Palavos said. "Typically in an arena like this, you would have a center cluster that would handle two-thirds of the seating bowl with some type of smaller two-way delay devices that would handle the upper seating areas. But these large beams hang down low and would be in the main cluster's coverage pattern, leaving portions of the audience out of the sound coverage."
WHJW's design called for a multi-cluster arrangement incorporating EAW AX344, AX364 and AX396 three-way, full-range arrayable install loudspeakers.
"There's a center cluster that consists of EAW SB528zp Large Format Subwoofers. Then there are two different styles of clusters," Palavos said. "On the north and the south sides there are four AX boxes with a single AX hung below for down fill. There's another large lateral truss running through the building, so on the east-west clusters they had to do this unique rigging solution that has a pair of AX boxes with a single down-firing AX box. That handles about half the seating of the facility. Then there are five AX boxes per side on the outside of the large roof trusses that handle coverage for the majority of the audience in the east-west portion of the arena."
A number of MK2399 two-way, full-range install loudspeakers provide scoreboard fill in the center of the arena, Palavos added, "and they do also have what they call the south stage clusters, which are two – one left, one right – AX396 enclosures that allow them to do some end-stage events like graduations and other things.
"WJHW not only did the electronics package design – speakers, wiring, consoles – but they also did a substantial improvement to the facility's acoustics," Palavos continued. "Bass traps are located down each side of the arena. As you approach the top of the seating area, the audience seating gets pretty close to the bass trap ceiling, which allowed us to install EAW CIS400 [two-way, 6.5-inch] ceiling loudspeakers for additional fill coverages."
"The system tuned up very quickly – much more so than anticipated, given the architectural constraints of the loudspeaker locations," said Graham. "This was a tough project with a lot of emotion involved, given the high number of complaints specifically directed at the old sound system (vintage 1975) and previous acoustical treatments, or lack thereof."
Originally the site of a fairground in the early 1900s, MetraPark (METRA is an acronym for Montana's Entertainment, Trade and Recreation Arena) is situated next to the Yellowstone River and covers 185 acres within the Billings city limits.
MetraPark's Rimrock Auto Arena hosts Montana's largest concerts, family shows, rodeos, ice shows, motor sports and other events, including local school and college sports tournaments and graduation ceremonies.
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