By Nheyob - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18432477
IMEG Corp. based in Rock Island, Ill., (formerly KJWW Engineers) reports that creative design solved long-standing acoustical and clarity issue at the 1,500 seat Saints Peter and Paul Cathedral in Indianapolis.
“We specified high performance, tall and thin linear loudspeakers, which are often used in large churches, but we added some unusual things in our design to improve clarity,” says IMEG Senior Designer David Wright. “We are both acoustical and AV consultants and we take that combined scope very seriously. In other words, we’re both AV and acoustic engineers who take it past average performance, yet keep a budget in line, too.
IMEG Designer Russ Hoppel modeled the room to predict and confirm performance prior to competitive bid issue. A commissioning and optimization step made a key difference at the end.
"It's as if the talker is next to you instead of 115 feet away. People connect to the message and can worship better. Millennials feel like they are not just in a huge room. The elderly hear well with a new hearing loop, as well. Everyone is more engaged." David Wright, Senior Designer, IMEG Corp.
Built in 1912, Saints Peter and Paul Cathedral’s rear seats are 115 feet from the front, and the ceiling is three stories high. It’s essentially a beautiful marble box. The cathedral – also renovated by Wright in 1987 – featured “a dated design where you stack a bunch of small background music speakers and put them in a metal screen with no (software) control,” Wright says. “The difference between that and our software steerable speaker arrays makes clarity pop. It's as if the talker is next to you instead of 115 feet away. People connect to the message and can worship better. Millennials feel like they are not just in a huge room. The elderly hear well with a new hearing loop, as well. Everyone is more engaged."
The cathedral features a pipe organ. The space is, of course, highly reflective with hard surfaces – which works well for the organ and choir but not for spoken word. “It also has a shallow transcept and a very deep Dais with Altar that audibly disconnect the natural talkers (Priest) from the congregant, and from the front loudspeaker reinforcement,” Wright notes, saying that destructive echo happens very fast in the space.
“You’d normally think a room like this would be a nightmare [since it's] so big. When a lot of people sing, it’s so inspirational but a completely different story for talkers because of the very high ceiling," he continues. "Design is the key."
Saints Peter and Paul Cathedral, Indianapolis, Blessed Sacrament Chapel, interior nave; image: Wikimedia Commons
Loudspeakers considerations
When a powerful loudspeaker “speaks” into such a space it’s like a laser, Wright reports, it may excite less reverberation as it hits limited wall area, but it can generate very late arriving echoes, which is worse.
“Sound travels 100 feet each way, so you’ve got a quarter-second echo, adding to a half second, one second, two seconds all adding like a machine gun,” says Wright. “The line arrays do multiple beam steering too and can diminish impact on many building surfaces. This is what people sell. But what’s more destructive is the echo it can create when it hits the back seats and farther, the rear glass doors. So you don’t want too much power and you must treat the room selectively for acoustics. With our predictive acoustic modeling we knew what to do well in advance. We always say AV products are not AV solutions and you just need good tools and experience in the tough rooms.”
"With our predictive acoustic modeling we knew what to do well in advance. We always say AV products are not AV solutions and you just need good tools and experience in the tough rooms.” David Wright, Senior Designer, IMEG Corp.
For these reasons, Wright’s team didn’t small choose symmetrical loudspeakers, as a good architect would love, he says. “You get better performance out of one taller speaker,” Wright continues. “You sacrifice in a space like this by using two short ones, too. It’s better to use [a] larger main speaker with a dummy enclosure for symmetry. There is better control, better imaging, less power plus a lower budget. Clarity improves and people hear, especially children and those with foreign accents. Design wins every time."
Speaker beam width
Speaker beam width was another consideration. “With all line arrays, the side dispersion is so wide that it’s hitting the closest available nearby at high power,” says Wright. “It’s actually most powerful when it hits the nearest side wall. That can become a fatal flaw. If you don’t account for that early, you’ve got another machine gun echo.”
Wright’s team designed a four-inch-thick, stretched-fabric acoustical panel to trap sound that would otherwise create destructive reflections.
Wright’s team designed a four-inch-thick, stretched-fabric acoustical panel to trap sound that would otherwise create destructive reflections. This pinpoint acoustical enhancement saved the day, he says, but also kept the space live to support worship. In addition, due to a smaller tech footprint, it conserved budget.
Wright’s team also “localized” the main speaker in software, so the main left position handles the left podium, where the talker is. “This is our trademark, and ‘localization’ or imaging to the source is as important as any other factor for design. The industry doesn’t use this technique," he says. "The distant rear seats are now some of the best seats in the house, and a side seat hears sound coming from one point.”
"... you can’t change laws of physics, but you can optimize them.” David Wright, Senior Designer, IMEG Corp.
Wright continues, “Further, the Cantor is directly in front of the loudspeaker (a clear challenge), and standing over two feet away from the mic but with no feedback, at least after commissioning the system you can’t change laws of physics, but you can optimize them.”
As for mounting a 100-pound speaker, “you cannot secure a loudspeaker to the Italian marble of a cathedral,” Wright states. “Sophisticated loudspeakers have to be almost perfectly placed. So, a short steel base was devised. The speakers were then custom painted to match the rose-striated Italian marble, which effectively hid the prominent front speakers and steel base and supported them from the floor alone.”
Wright concludes, “The result is a resounding success. You must do more than just stick the loudspeakers in a room and aim them. Catholic liturgy and architecture is demanding. With the Saints Peter and Paul Cathedral sound system, you get the beam control and balance – yet it’s visually appealing and it sounds so clear. This cathedral will benefit for decades.”
