Installation Profile: AV Update
Nov 1, 2008 12:00 PM, By Dan Daley
Architectural firm RTKL redesigns the U.S. Naval Academy’s historic mess hall with flexible AV.
The video system is rounded out with the Sony PTZ camera, which is positioned in the center section of the hall — referred to as the “anchor” of the building complex — and suspended from the ceiling and focused on the ornate central podium that is used for daily announcements. Its signal can feed all 74 screens through the Magenta Research distribution system, and it can be routed to other video systems on the campus.
A Tascam DV-D6500 DVD player and VBrick MP2D-STARMPEG-2 dual-channel decoders are other input sources for the video system. Switching is controlled via a pair of Crestron TPS-12G-QM 12in. touchpanels and an AV2 processor. The larger 12in. screen was chosen to keep the GUI uncluttered and more user-friendly. Control of the LCD screens is supported with 74 Extron IPL T SI serial-to-Ethernet converters and four 24-port Cisco Ethernet switches. Crestron Enterprise RoomView software allows facility maintenance to monitor the operational status of all 74 displays remotely from elsewhere on campus. Switching is located in the anchor and in the hall's dedicated equipment room. Each wing is its own zone with its own signal, allowing each wing to be used as a conference room or classroom when necessary.
The Magenta Research distribution system makes use of traditional Cat-5e cabling rather than skew-free cabling. Because the Magenta equipment incorporates onboard skew adjustment, this decision was made in order to support voice and data needs as well as any necessary future requirements. As part of this plan to implement a versatile cabling infrastructure, RTKL chose to have all UTP cabling and terminations provided and installed by the telecom contractor, PrimeNet, rather than the AV contractor.
“We believe that the single greatest point of failure of UTP distribution systems is in the quality of the cabling and termination,” Warner says. “While there are exceptions, the AV industry continues to have inferior skill sets in this area [compared to] the telecommunications industry. Using this approach ensured that we ended up with a certified cabling system.”
TIGHT FIT FOR AUDIO
It's already been established that the wings of King Hall are long and low-slung, but they have another dimensionality that proved to be a challenge for audio: A large skylight runs down the center of each wing, limiting space for in-ceiling loudspeakers. However, almost anything would have been better than the ancient, basic, single-microphone PA system the hall had been making do with.
“Part of the mission was to bring the hall's media systems up to par with the technology in the rest of the school,” Warner says. “The distributed sound system had to be part of that.”
That might not have seemed difficult at first; the old system had several blown drivers that had been unable to handle the SPL needed to intelligibly fill the wings or the anchor. Warner had used Tannoy loudspeakers in similar situations, but he found that his first choice wouldn't work because the larger loudspeakers were not suitable for a blind-mount situation into the pre-cast GRFG ceiling.
The next choice was the Tannoy CMS601 70V ceiling-mount loudspeaker, which has an all-in-one back enclosure. These were installed after RTKL AV techs had checked their polar patterns on a CAD rendering of the space. Between the skylights and other architectural impediments, Warner acknowledges that the loudspeaker part of the design required some necessary compromises.
“Speaker placement and spacing was not perfectly ideal, but by capitalizing on the curvature of the ceiling, we achieved a system that is stable and intelligible — a marked improvement from what the hall started with,” he says. “However, the ability of the Tannoy driver to deliver and handle a higher SPL helps significantly offset that, and the curvature of the ceiling actually works in the audio's favor by angling the loudspeaker inwards toward the room's center line, thus improving its overall dispersion pattern.”
Given the size and configuration of the space, the antenna for the PA's integrated wireless microphone system required that it be mounted remotely. However, a standard two-antenna system wouldn't be sufficient for this kind of space configuration. RTKL worked closely with Shure to design an eight-antenna combining system that could support all of the various zoning configurations. In order to expand the number of antenna, but still keep it contained and more manageable within a single wireless system, a Shure ULXP24/85 wireless microphone system was configured with eight UA830WB remote antenna throughout the hall linked via a Shure UA221 passive antenna combiner. Processing and management is handled with a pair of Biamp Nexia CS audio DSP systems that route through a Bittree patch panel.
One other aspect worked in audio's favor: Despite the potential acoustical nightmare of hundreds of feet of parallel hard-surfaced walls and floors, they are generally used en masse by the students and faculty, which causes its own acoustical damping.
“Forty-eight hundred people sitting down in the same place at the same time presents some significant acoustical treatment,” Warner says with a smile.
Overall, the King Hall renovation at the Naval Academy was one of the smoother government projects that Warner has experienced, citing good site access and a generally helpful attitude on the part of the school. “It wasn't as complicated as trying to do something similar, say, at the Department of Defense,” he says. “But all government facilities have their own special challenges, including keeping the AV design and installation in tune with the aesthetics of the building, which often turns out to have some historical aspects. Expect to take a bit more time than a similar nongovernmental project” — King Hall's work had to be split into two phases over two years so as not to disrupt academic activities — “and anticipate a lot of coordination between architecture, engineering, and AV design.”
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