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Precise Audio Directivity

A crucifix-shaped sanctuary, high ceilings, and rear glass wall set the bar at Greentree Community Church

For 17 years, the congregants of Greentree Community Church gathered on Sundays at the North Kirkwood Middle School or other schools in the district. That changed last fall, when the congregation celebrated Sunday services for the first time in the church’s new building. The building’s design is a modern take on the classic crucifix shape, with transept-like spaces on either side that can be divided into separate rooms for classes and other events, and a configurable sound system featuring Fulcrum Acoustic loudspeakers. 

Services and other events at the contemporary Evangelical Presbyterian church feature many kinds of music—voice, violin, piano, and a full amplified band with drums. The sanctuary, which seats approximately 400, has a flat floor and employs stackable chairs rather than permanent seating, allowing the space to be used for multiple purposes. 

The sanctuary’s high ceilings and glass rear wall created some acoustical challenges, explains Ryan Knox of Idibri, the Dallas, Texas, firm behind the audio, video, and lighting systems, and the acoustical treatment. “The entire back wall is glass and hard surfaces,” says Knox, “and the beams where the speakers are mounted are about 16ft. above the floor.” 

Although a motorized acoustic shade can be lowered over the windows for privacy and to reduce reflections, “it was very important that we not throw a ton of energy at that back wall,” relates project manager Brian Turnbull of Palatine, Ill., systems integrator Amplio Systems, which installed the system. 

Knox addressed the main space’s challenges by flying two pairs of Fulcrum Acoustic DX1595 dual 15in. coaxial, passive loudspeakers, which have 90° x 45 dispersion. One left-right pair is mounted on a truss above the stage, while a second pair of delayed DX1595s is mounted halfway back in the room. Four Fulcrum Acoustic RX699 6.5in. coaxial loudspeakers are mounted on the stage lip as front fills. 

“Fulcrum Acoustic has an excellent product line for this type of space,” Knox says. “Their tight pattern control and advanced processing enabled us to direct their energy on the congregation rather than on the glass rear wall. 

“The system is visually exposed on the beams, so having a high-performance, high-powered system in a small, low-visibility package was a significant benefit.” 

The two small side areas-not conventional transepts but similar in appearance-can be divided from the sanctuary, providing additional spaces for classrooms and other needs. “We had to get creative and set those rooms up so the speakers could be used as part of the main system and as stand-alone system for conferences, classrooms, and so on,” recalls Turnbull. Fortunately, the walls, ceiling, and carpeted floor in those rooms are fairly absorbent, so although the side rooms are acoustically different from the main sanctuary, they don’t create audible issues. To serve these two rooms, Knox selected four Model S dual 8-inch coaxial loudspeakers. 

All loudspeakers employed at Greentree are passive. Power and DSP are supplied by a QSC Q-SYS system. “System tuning was pretty straightforward,” notes Turnbull, “because the Fulcrum Acoustic presets did most of the work for us.”

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