In a crowd-filled venue, the ability to clearly understand emergency announcements and instructions can literally be a matter of life or death. That's why the National Fire Protection Association included a voice intelligibility requirement in NFPA 72, the National Fire Alarm and Signaling Code. Widely adopted by jurisdictions across the country, the code mandates mass notification systems for "acoustically distinguishable spaces" and specifies intelligibility standards for those spaces. As Boston's Communications Design Associates, Inc. recently found when designing a sound upgrade for the city's John B. Hynes Veterans Memorial Convention Center, Electro-Voice is the only loudspeaker manufacturer that can deliver the required intelligibility in high-ceilinged spaces requiring long-throw horns.
"Back in 1988 I designed and installed the original sound systems at the Hynes Center," recalls CDA principal consultant Greg Vincent. "After 21 years, it was time for an upgrade, so they contacted us several years ago to design replacement systems. The added twist was that we had to bring the building up to present code, and in doing so we had to meet the intelligibility requirements of NFPA 72 2007 Edition."
The sound system upgrade, installed by ADTECH Systems of Sudbury, Massachusetts, covered a wide variety of rooms within the 352,000 square foot facility, including a divisible grand ballroom, a 3000-seat auditorium, and several large exhibit halls. In some of these larger spaces ceiling heights reach nearly 60 feet. "The greatest challenge in terms of meeting intelligibility requirements was in those larger, taller spaces," Vincent says.
To meet the requirements, CDA started by modeling various manufacturer's loudspeakers in EASE. "Because the spaces are large, open, and highly reverberant, it really required speakers with great pattern control," Vincent says. "In shopping around and looking at specs we realized that the large-format horns from Electro-Voice seemed to have the best pattern control. In fact for the tallest rooms it turned out that the EV horns were the only product that could meet the standard."
The Electro-Voice horns were sourced through New England Electro-Voice manufacturer’s representative AudioPros of Charlton, Massachusetts. Because the State of Massachusetts owns the Hynes Center and sole sourcing is typically frowned on in public procurement, CDA was required to provide detailed documentation in order to justify including only Electro-Voice horns in the bidding specifications for the taller rooms. "We ended up putting in the specifications that these were the only loudspeakers that could be used. If the contractor wanted to substitute something else, they would have to bear the expense of another modeling process to prove that it would still be compliant."
The largest of the horns were MH4020ACs coupled with ND6X-8 compression drivers and AT-100 transformers. "The pattern of those horns is so well defined," Vincent says, "that even at long distances you can walk in and out of it and really hear the difference. There's no way to get that control at those distances with other manufacturer's horns." Twenty-five such horn/driver combinations were used in Exhibit Hall D and another 16 in the Auditorium. In Exhibit Hall C, meanwhile, CDA specified 84 of a slightly smaller Electro-Voice horn, the MH660AP. Once again, Vincent says, the Electro-Voice horn was "the only thing that could give us what we needed in that room."
In the Auditorium the Electro-Voice horns were supplemented with 13 Xi-1082 ultra-compact, two-way full-range loudspeakers for under-balcony coverage and 12 EVH-1152S/96 two-way coaxial full-range high-efficiency loudspeakers for the balcony. "We wanted to keep all parts of the room voiced the same rather than mixing loudspeakers from multiple manufacturers," Vincent says. "You can walk from the main floor into the under-balcony area and it all sounds consistent. And the same is true of the large balcony seating area, which is covered very well by the 1152s. The EV systems are all voiced to work very well together."
Eighteen cabinets of a different 1152 variant, the EVH-1152S/66, are used in the ballroom. "For the ballroom, we needed not only the intelligibility but a musical quality as well," Vincent says. "We auditioned products from several manufacturers, and we really liked the way the 1152s sounded. We modeled it, and it met the intelligibility requirements, so we went ahead and specified it for the bid."
Vincent says that throughout the process Electro-Voice went "above and beyond" to ensure success. "They gave us a lot of assistance. They reviewed our modeling and made recommendations as far as equalization to optimize for their cabinets. That type of support from a manufacture is invaluable to a consultant. Also, the Center was in full use, so we really needed good coordination to get the systems installed. EV was really great about staying on top of shipment dates, and AudioPros was also very instrumental in helping everyone work as a team to pull this off in a timely fashion."
With the Electro-Voice systems now all installed, Vincent says, "we've passed all the proof-of-performance tests for intelligibility in the large high ceiling spaces with no problems. The systems have been running great, and the client loves the sound quality. They are very happy with these systems."