Decentralized Sound Takes The IceThe Olympic Oval in Calgary gains significantly upgraded sonic performance and enhanced system flexibility. 10/17/2007 6:55 AM Eastern
Decentralized Sound Takes The Ice
The Olympic Oval in Calgary gains significantly upgraded sonic performance and enhanced system flexibility.
CHALLENGE: Replace an existing, underperforming point-source system with a new design providing dramatically improved coverage, as well as venue-wide sound reinforcement and the capability to simultaneously support multiple events in a massive indoor arena.
SOLUTION: Create a widely distributed approach that eliminates critical distance issues, with a digital backbone and networking to provide system zoning and, when desired, localized control.
The Olympic Oval in Calgary, Alberta, Canada, in perspective, with hundreds of thousands of square feet of athletic facilities under one roof. The ceiling catwalks circling above the surface proved to be an ideal mounting location for the majority of loudspeakers on the project.
On a list of unusual installed sound reinforcement situations, the Olympic Oval in Calgary, Alberta, Canada, would rank near the top, as evidenced by a recent project that saw the venue's original sound system replaced by a widely distributed, multi-zone design to serve a decidedly unconventional indoor arena.
Constructed for the 1988 Winter Olympics, the venue is a pre-cast, pre-stressed concrete structure that completely covers a 400-meter, long-track speed skating oval that surrounds two international-sized ice rinks: one for short-track speed skating, the other for ice hockey.
The original PA system relied upon a main centralized loudspeaker cluster comprised of larger format horns and compression drivers — the most common and accepted large-venue sound reinforcement approach two decades ago — to provide coverage to the grandstands. But this system's time had long passed, and increasingly, supplemental rental systems were required in order to meet major-event expectations.
Seeking an upgrade, Kameron Kiland, the Olympic Oval's director of operations, began discussions with Terry McConaghy, general manager of integrated system sales for Allstar Show Industries, a leading installed and portable system provider with offices in Calgary; Edmonton, Alberta; and Vancouver, British Columbia. Allstar was no stranger to the challenges of the Oval, having been a primary provider of the supplemental rental systems, plus, the company has a rich heritage of supplying top-shelf design-build solutions to large venues.
“From an operational expense standpoint, [Kiland] realized it didn't make much sense to continue to finance supplemental systems on a regular basis. A new system would pay for itself within five years, and likely even sooner than that,” McConaghy explains. “He also had a vision for what a sound system could do in terms of dramatically enhancing flexibility throughout the venue.”
In addition to dramatically improved coverage to the grandstand, Kiland sought venue-wide sound reinforcement, extending even to ancillary office areas. Further, he wanted the new system to be capable of simultaneously supporting multiple events, along with the ability to plug in localized control and source devices.
“The primary impediments to this approach include the close proximity of these areas, the fact that physical barriers can't be erected to acoustically separate them, and that the overall scale of the venue dictates rather long-throw requirements from loudspeakers,” McConaghy says. “We arrived at a design approach centered upon widely distributed loudspeakers offering exceptional directivity and control of output, where sound to each coverage area — or zone of the system —would need to be clear, present, and intelligible, but then drop off very quickly immediately outside of the direct field.”
Subsequent discussions of the project with SF Marketing, a leading distributor of pro audio products to the Canadian marketplace, as well as Joe Fustolo, head of the EAW Application Support Group (ASG), helped firm up this direction.
Arthur Skudra, a veteran electro-acoustic design consultant based in Hamilton, Ontario, was also invited by SF Marketing to join the system team, focusing on the exacting process of loudspeaker selection, location, and positioning throughout the entire venue. He started his design process by visualizing a widely distributed system and then whittled it down to smaller discrete “sub-systems” that would optimally serve their respective regions.
”I briefly considered a line-array approach, where a high-Q characteristic might overcome critical distance issues, but that would be very expensive. And in a place this big, even line arrays would still have a hard time overcoming critical distance,” Skudra explains. “It came down to one viable way to do it to meet the client's needs, and that was distributed, with a whole lot of loudspeakers to prevail over the critical distance issue.”
Comprehensive EASE modeling assisted in sorting things out. The ASG team conducted the painstaking process of translating the original printed architectural plans of the facility into AutoCAD, which then served as the basis of the EASE effort by Marc St-Jacques of SF Marketing. In the modeling process, Skudra focused in particular on what happens in coverage areas located between loudspeakers. Often, he says, when time alignment is not optimized between adjacent loudspeakers, there can be an “echo” effect and other intelligibility compromises.
“My goal on this project was keeping the impulse time at 30 milliseconds or less between any two adjacent loudspeakers,” he notes. “This isn't simply a matter of setting delay times in digital processing, but painstaking placement and aiming of the loudspeakers.”
Two ceiling catwalks (inner and outer) running above the oval surface proved quite opportune as mounting positions for most of the system's 66 EAW AX Series (longer throw) and MK Series (shorter throw) full-range loudspeakers. They're positioned to cover at least a dozen different areas that are broken down into zones.
First focusing on coverage to the grandstands, Skudra chose to attach loudspeakers to the outer catwalk that is closer (and lower) to the seating, presenting an acceptable critical distance of up to 12 meters (a little over 39 feet). These loudspeakers fire almost straight down in providing coverage from the front row to the back, while energy does not reflect off the back wall.
The EAW MK2364 two-way loudspeakers chosen for this task are located approximately 12 meters apart, with their 60-degree-by-40-degree horns rotated so that the cabinets can be mounted in a lower profile horizontal orientation when needed.
The inner catwalk, higher above the floor at about 18 meters (59 feet), proved an optimum position to mount a variety of loudspeakers to handle various event regions. To provide coverage on the lengthy straightaways of the speed skating long track, EAW AX344 loudspeakers, again spaced at about 12 meters, provide coverage up to an “edge of critical distance” of approximately 25 meters (82 feet). They transition to AX396 loudspeakers for each the two “end zones” of this track, selected because their wider horizontal dispersion (90 degrees) helps better spread the coverage over these wider, curved spaces all the way into the corners of the grandstand.
An EASE plot of the Olympic Oval in Calgary shows the location of every loudspeaker installed within the arena. Sound pressure level predictions are represented by different color outlines.
Using both sides of the inner catwalk, four more AX396 loudspeakers (two per side) are dedicated to the skating short track, and the same approach was duplicated with the hockey rink. These are mounted at a steep down-angle to avoid generating reflections off of ample amounts of nearby ductwork.
“Being aware of the critical distance for every loudspeaker in the system, and keeping in mind what is happening with adjacent sounds that might also reach listeners, was the key,” Skudra says. “Discrete echoes resulting from placing a loudspeaker too far away from its intended listeners would have compromised the quality we were all seeking.”
The six-week system installation process was headed up by Keith Watson of Allstar, with the venue's constant use every day of the week dictating workdays starting at 10 p.m. and lasting until 5 a.m. The crew used 85-foot lifts to reach the ceiling over the ice surfaces.
The sheer scale of the system, as well as the number of point sources it employs and the requirement for multiple zoning capability, dictated a sophisticated digital backbone to manage and tie it all together. In consultation with SF Marketing, Allstar settled on a Symetrix SymNet Express Cobra System, a series of digital signal processors (DSP) that are controlled by SymNet Designer software.
Joining the system's 18 QSC CX Series power amplifiers, a configuration of four 4-input by 12-output Express Cobra units are rack-mounted in a remote equipment room. These units can be remotely addressed and controlled over Ethernet, and they also support 16 inputs and 16 outputs of CobraNet audio over Ethernet, in addition to analog I/O.
Companion SymNet ARC wall panels —installed at several locations and linked via CAT-5 cable — provide simple user control of a system. For example, one channel of analog audio can be routed to or from an ARC panel for simple paging or monitoring needs. In addition, the Express Cobra units are also outfitted with an RS-485 port for extending ARC and external control capacity.
“One of the unique things about this system is that it has six paging locations, and an ARC panel at each of these locations provides audio over the RS-485 control bus just by pushing a button,” explains SF Marketing's Rob Deslauriers. This interface and networking capability also allows for easy routing of program material from a radio dual tuner to various zones in the system via RS232, even to distributed ceiling loudspeakers in front office and conference room areas.
Eight more ARC panels are also permanently positioned around the venue to serve as local inputs, allowing a portable system — Shure UHF wireless microphones, an electronic start gun and a pair of EAW FR129 compact loudspeakers — to be located at race start positions. “As a result, there's local audio right at these crucial positions, and this program material can also be fed to the designated zones of the main system,” Deslauriers says.
The installation crew worked around the old system, which remained operational until it could be removed after the new system had been activated. Skudra returned to the venue immediately following installation to perform three nights of system tuning and optimization, and he was one of the first audio professionals in the world to utilize new EAW Smaart v.6 measurement and analysis software on a live project (see sidebar). EAW's Fustolo also provided his input in the commissioning effort, and ultimately, the final performance results proved startlingly effective, perhaps even surpassing the team's expectations.
Writer/photographer Keith Clark has been covering AV technology and applications for more than 20 years. He can be reached at firstname.lastname@example.org.