Chapel Adds Invisible AV
Retractable display lifts and in-ceiling loudspeakers installed in an Australian school enable its AV system to remain unobtrusive.
CHALLENGE: Design an AV system for a chapel that can accommodate modern presentation requirements while remaining hidden during traditional services.
SOLUTION: Install a custom, retractable plasma lift, in-ceiling loudspeakers, and a pocket-sized wireless control system.
WHEN CONSIDERING options for the AV system in its new chapel, Caulfield Grammar School in Victoria, Australia, wanted a modern system that would also preserve the sanctity of the chapel. As part of a campus-wide construction project finished in late 2004, this balancing act inside the chapel created a few AV design and installation challenges. The chapel needed a system that could deliver presentations, training events, and youth-oriented services with full audio and video without detracting from more traditional activities such as funerals and worship services.
To devise an effective solution, school administrators and the project's electrical engineering consultant, Adrian Newman and Associates, turned to Daniel Baldwin, director of Victoria, Australia-based AV supply and integration firm Dr Audio Group, to serve as project manager, and Wayne Schultz, lead integrator at Victoria-based AV solutions company Insight Systems, to work with the electrical consultants and prepare the original project proposal.
The basic system called for plasma displays fed by VHS tape decks and DVD players, along with a high-quality audio system. Although the desired source components were pretty standard, logistical and aesthetic requirements complicated the project. “The display devices needed to be seen from any location in the room,” Baldwin says. “But the client didn't want the screens to be visible if they weren't being used. Computer inputs needed to be wireless, and all other source equipment needed to be housed in a rack in another room, and controlled through a wireless interface.”
Additionally, the school didn't want the room's inverted pyramid ceiling to have any penetrations, but its desire for the components to be hidden coupled with sound quality concerns didn't allow for surface-mounted loudspeakers. “The architect decided that loudspeakers on the side of the room would be preferable, but we fought the idea with point-of-origin issues,” Baldwin says. “We wanted to ensure that the congregation watching the screens in the center of the room didn't have the sound coming from behind them.”Concealed audio
With the school's constraints and expectations in mind, Shultz and Baldwin decided to install four Sound Advance SA2-4B invisible speakers with back boxes — one in each quadrant of the ceiling's inverted pyramid structure.
“These fit flush with the plaster, and can be painted the same color as the ceiling,” Baldwin says. “The result is a full-range speaker that appears invisible.”
Once the loudspeakers were selected, placement became the next concern. “We used CAD drawings showing vertical and horizontal aspects of the chapel,” Baldwin says. “We overlaid speaker plots that showed the coverage and SPL levels as indicated by the manufacturer. By manipulating the locations of the speakers, we found the ideal placements.”
The chapel also needed wireless microphones, so clergy and outside presenters could move freely around the room. Shultz installed three Chiayo UHF wireless microphone systems with an antenna splitter/divider. He also installed an AKG GN30E gooseneck microphone with a CK31 cardioid microphone capsule to a mobile lectern that can be brought in and connected to the Chiayo wireless system. The microphone signals, along with a Sony five-disc CD player, are input in to an Inter-M PP-9214 12-channel mixer, which routes the audio to any combination of the four Sound Advance loudspeakers. An NAD T163I AV tuner preamplifier was also added to control source selection and source audio levels.
Schultz says the Sound Advance speakers and wireless microphones helped achieve a nearly invisible audio presence, but didn't adequately provide enough low-frequency level for the room. To address this, Shultz added four Bose FS3B Acoustimass subwoofer modules with ceiling kits, which are invisibly ported to the side of the room. Shultz also used a Sabine GRQ3102 feedback eliminator to enhance sound quality.
“The system was tuned without the feedback eliminator being active, and once the system was signed off, the eliminator was engaged,” Baldwin says. “This ensures that the Sabine product eliminates any errant feedback that could occur due to microphone placement, but that it doesn't tune the room.”
In the control room, a 40 RU rack contains the remaining audio components, including an Australian Monitor SY800 power amplifier, two SoundTech STPS802 amplifiers, and a McLelland CX152 crossover and CP102 compressor.Retractable video displays
While room structure played a large role in the placement and design of the chapel's audio system, the primary concern with its video system was line-of-sight considerations for a number of possible room configurations. “The chapel needed the ability to be arranged in any format from a central position in-the-round, to a focus at the front, rear, left, or right of the room, depending on the program,” Baldwin says.
After considering several options, the design team found that one solution wouldn't solve the problem for all room configurations, but because the majority of video-reliant programs called for an in-the-round seating configuration, the middle of the room became the best option for mounting the flat-panel displays. Shultz installed four 50-inch NEC PX50XMW plasma displays — each mounted at a right angle to the next on a custom display lift, designed and built by Victoria-based motorized lift manufacturer Ultralift Australia. The lift lowers the screens into the center of the room, and tilts them forward to provide optimal viewing angles. Video signals from a Sony DVPNC625 DVD player and SLVEZ725 hi-fi VCR are wirelessly sent to the four displays via a Linksys WPG54G presentation player. However, Baldwin says the wireless system does have one drawback (see sidebar).
“The only limitation of this device is video being played from a PC,” he says. “The Linksys unit operates over a wireless network using 802.11b transmission rates. This standard isn't at a speed that allows video from a PC to be transmitted over the wireless network without artifacts or glitches.”Portable control
Once the audio and video system challenges were addressed, Shultz and Baldwin turned their attention to the room's control system, which also needed to be concealed, depending on the use of the room. “The interface was to be wireless, simple enough for the chaplain to use, and small enough to be carried in their clothing,” Baldwin says.
Shultz and Baldwin chose an AMX NI-3000 integrated controller, along with an AMX AXR-RF receiver and AMX TXC-16+ remote control. “The AMX control system provides wireless control of the whole AV system, including lifts, plasma screens, source equipment, volume, and lighting,” Baldwin says.WIRELESS VIDEO TRANSMISSION
Wireless video transmission in the chapel at the Caulfield Grammar School in Victoria, Australia, faced limitations due to the 802.11b operating protocol of the Linksys WPG54G wireless presentation player used in the project. The 802.11b protocol's lack of data transmission speed when transmitting video from a PC would have resulted in video glitches, according to Daniel Baldwin, project manager for Victoria-based Dr Audio Group.
These inherent wireless video transmission issues are expected to be relieved by the soon to-be-released 802.11n WLAN standard from the New York-based Institute of Electrical and Electronics Engineers (IEEE). However, Matt Nelson, director of marketing at Huntsville, AL-based embedded technologies company Avocent, and former wireless consultant, says the 802.11n standard might not be the cure-all that some people are predicting.
Nelson says that while there are provisions such as increasing the connection speeds to up to 600 Mb/s to address performance issues, it's the protocol's frequency that could result in continued wireless video transmission problems. “802.11n will run along with 802.11b/g, Bluetooth, and other protocols on the 2.4 GHz space, which is a very crowded frequency,” Nelson says. “It's my contention that people who operate in that frequency will always have issues with regard to video quality. Fixed image transmission will work in 2.4 GHz, but with video, you end up dropping frame-rate performance to less than 10 f/s, or you end up dropping color depth.”
Nelson says an alternative solution could lie in the less-often used 801.11a protocol, which operates in the 5 GHz frequency. “The big difference in the 5 GHz space and the 2.4 GHz space is that there are 12, clear, consecutive channels available in 802.11a,” he says. “In 802.11b, there are only three channels, and while people will tell you that there are 12 channels in 802.11g and that there will be even more in 802.11n, those are overlapping channels. And overlapping frequency means that you've got other noise existing in that same channel.”
Paul Kramer is associate editor of Pro AV magazine. He can be reached at firstname.lastname@example.org.