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An Elegant Solution
- by Christopher Buttner and Michael Schwartz
- Sound & VIdeo Contractor
Using CobraNet and fiber optic-based audio networks to transport multiple, noise-free audio channels and overcome complex routing challenges at the Sydney Opera House.
Built on Bennelong Point in Sydney Harbor, one of the most beautiful sites in the world, the Sydney Opera House is probably the most famous and architecturally unusual building in Australia, if not the world. Its signature design, resembling the windblown sails of a giant ship, is a landmark easily recognized as one of the premier performing arts centers in the world. Since it opened in 1973, the Opera House is among the world's busiest. Some 3,000 events attract as many as two million patrons annually, not including the hundreds of thousands of tourists who visit the complex. The 4.5 acre (1.8 hectare) complex houses nearly 1,000 rooms and five performing venues for a seemingly endless variety of arts programs—from traditional theatre, opera, dance and music programs to contemporary art exhibitions, programs and films.
The recent completion of the SOH's newest stage—The Studio, a 400-seat multi-purpose venue—also marked the completion of a new paging and communications system, designed and installed by The PA People, a prominent Sydney-based systems integration firm, and Creative Audio, its sister organization in Brisbane, Australia. Solving complex routing and distribution challenges is not new for The PA People. The company recently installed a CobraNet system in the Sydney Olympic Stadium in preparation for next year's Olympic Games. The SOH system is a centralized DSP-based digital audio network built around QSC RAVE (Routing Audio Via Ethernet) and Peavey MediaMatrix hardware, and it is a prime example of how fiber-based audio networks can ensure that multiple audio channels are transported free from noise, even in the most complicated routing situations.
Five stage manager desks, one located in each of the main performance venues, serve as the primary source of paging announcements. The desks control not only paging, but also lighting, video monitors and intercom functions.
Inside the house
Five performance venues (listed in descending order of size), the main Concert Hall, Opera Theater, Drama Theater, Playhouse and The Studio, range in seating capacities of 2,700 to 400. The complex also houses an elaborate maze of rehearsal studios, eateries, lounges, dressing rooms, administrative offices and numerous mechanical equipment rooms.
Routing audio throughout this complex, multi-purpose facility posed several challenges to The PA People. The system had to be versatile enough to handle multiple audio inputs and control sources simultaneously, large enough to distribute audio to 65 remote paging zones, and flexible enough to satisfy the individual production communications requirements of each venue and peripheral support areas. Also, as with all paging systems used partly for emergency purposes, it had to be virtually failsafe.
The Opera House is located 820 feet (250 m) from the main shipping lines of Sydney Harbour
- an extremely high electrical noise environment
- making it susceptible to interference.
Plus, there was a significant amount of electrical noise radiation within the building, said Chris Dodds, managing director of The PA People. Fiber optic cabling, which is free from ground loops, totally immune to EMI and capable of redundant operation, proved to be the ideal choice for the job.
"To meet the design requirements that were proposed," Dodds said, "we clearly needed a fiber optic-based signal distribution solution. We have found CobraNet and the QSC RAVE/Peavey MediaMatrix combination to be a useful solution to a number of difficult audio signal transport, distribution and signal processing/routing problems. QSC Audio was the first to have a CobraNet solution available with its RAVE system, and we have been more than happy with the product and their support throughout this project."
Key components of the paging system, all designed and built by Creative Audio, are controlled on a 10Base-T data distribution network, separate from the CobraNet audio network. Paging control components include six custom-engineered consoles for stage and production managers, multiple paging stations that control pages in various zones, a Digital Message Store and forward system (DMS121), which stores pre-recorded paging announcements; loudspeaker control panels and remote-controlled mic preamps. Other system devices include auditorium mics, program sends from the venue mixing consoles, local mixers, ambient noise level sensing (ANLS) mics and monitoring mics for the foyer and dock areas.
At the heart of the audio system is the 100Base-T fiber optic network established using QSC RAVE digital signal transport units and Fast Ethernet hubs. The entire system is fully redundant to ensure that the signal path remains intact if the primary network fails. A separate 10Base-T data distribution network, which is not connected to the audio fiber network, is used for system control purposes.
Audio network: CobraNet configuration
The audio network is basically arranged in a star configuration. At the center of the star is the central control room, which houses two redundant MediaMatrix systems. MediaMatrix handles all audio signal routing for the paging system as well as such audio processing functions as equalization, compression and dynamics. The endpoints of the star topology are eight outlying audio racks located throughout the complex that house various components of the fiber and data distribution networks. A fiber optic-based RAVE digital audio network routes the audio between the locations.
The RAVE88s in the central control room each handle up to eight AES/EBU digital inputs and outputs and interface with the MediaMatrix via an AES/EBU daughter card interface, ensuring that the audio remains in the digital realm throughout the network. Outlying audio racks contain a RAVE188, each handling as many as eight analog inputs and eight analog outputs. Paging audio signals, whether prerecorded messages, live announcements or such miscellaneous sounds as bells or chimes, are routed through the RAVE188 inputs to the MediaMatrix, where they are processed and routed back through the network to the paging amps and loudspeakers.
Eight RAVE88 units, which handle up to eight AES/EBU digital inputs and outputs, are located in the central control room. These interface with the MediaMatrix system via an AES/EBU daughter card interface. thereby ensuring that the audio remains in the digital realm throughout the entire network.
RAVE uses CobraNet technology to route audio over standard Ethernet hardware and cabling. CobraNet, a digital audio networking technology developed by Peak Audio, Boulder, CO, has been licensed to a growing number of pro audio manufacturers. It uses standard Fast Ethernet 100Base-T computer networking equipment to distribute up to 64 channels of uncompressed 20 bit digital audio over hub-based networks. CobraNet can transmit up to 64 channels through a single, inexpensive CAT-5 network cable or fiber optic cable. Because CobraNet uses off-the-shelf Fast Ethernet 100Base-T hubs and minimal cabling, hardware and labor costs involved in an installation are significantly reduced.
Two servers independently monitor the operating status of each MediaMatrix machine using the built-in "runtime diagnostics" feature. If a fault is detected in the primary machine, the server switches over to the secondary machine. This ensures that in the event the primary system fails, it will make a seamless transition to the secondary unit without an interruption to paging system operations. MediaMatrix runs MWARE, a software control program, and Peavey Architectural Acoustics Serial Handling Adapter (PASHA). This allows each MediaMatrix machine to be controlled through its two RS-232 ports from a rack-mounted PC, referred to as "the MediaMatrix server," and a special MediaMatrix Monitor panel (MMM3) made by Creative Audio. The MMM3 is an embedded PC-based device that communicates with the MediaMatrix machines via an RS-232 connection. It accepts a single balanced audio input, which is the monitor audio for its front panel loudspeaker. The MMM3 uses the PASHA control protocol to instruct the MediaMatrix machine to deliver the desired audio source to its monitor input. Two MMM3s are used, one for each MediaMatrix machine.
Data distribution network paging sources and control
Paging system control data is transmitted on a separate 10Base-T data network, which is not connected to the CobraNet audio network. (CobraNet requires a dedicated network using 100Base-T Fast Ethernet.) Each processor hooked to the data network is equipped with two 10Base-T compatible network interface cards (NICs). These run in parallel and are used to satisfy system redundancy requirements. A QNX OS, a real-time 32 bit UNIX-style operating system customized by The PA People and Creative Audio specifically for this installation, runs on each of the networked processors and will automatically load share between the two NICs. If one fails, it will immediately and transparently divert all traffic to the operational device. Embedded processors are built into each of the stage managers' desks and their associated node racks as well as the data servers located in the production manager's office and the central control room. These are all connected to the network using a star-configuration LAN.
Five consoles serve as the primary source of paging announcements. The consoles, referred to as "stage manager desks," are located in each performance venue and accessed by individual stage managers. Each console is a custom work surface to control not only the paging systems, but also timers, cue lights, video monitor source selection, intercom and LED signage. A sixth operating position is located in the Opera House's production office.
Five paging stations throughout the complex are the secondary source of paging announcements. These stations service areas not included in the zones controlled by the consoles. Loudspeaker levels, monitoring mic levels and other network devices can be adjusted from more than 125 control panels at various locations.
Each stage manager desk interfaces with the paging system via the embedded server located in the node rack for each venue. The servers, which run QNX software, are connected to the data network via two interface cards. This provides a redundant, fail-safe data path in the event of a failure. Stage managers can route paging requests to the MediaMatrix server, upload and download desk configuration information from the production office, and indicate engaged paging zone groups.
The production office console uses a PC-server setup with a standard keyboard monitor mouse interface using QNX. It is accessible via TCP/IP link with servers connected to it. The console also allows for remote configuration of each stage manager console and each paging station, and it provides a mechanism for indicating and logging system faults. The file server itself is connected to the system via the 10Base- T data network. The QNX network and file manager supervises the transfers over this connection to and from the other data nodes. The file server also holds the configuration files for the stage manager consoles and paging stations. These can be accessed by other nodes on the network according to the read/write privileges assigned to them.
The monitors for the two MediaMatrix systems, QNX CPUs, and two MM3 MediaMatrix monitor panels are housed in the central control room racks
Monitoring control
Each stage manager desk has two audio inputs (a monitor input and theatre communications input) and three outputs (for paging, public address and theatre communications). Monitor inputs originate from five sources—auditoriums, foyer areas, prerecorded announcements and sounds and paging stations.
In each of the five auditoriums, a stereo mic pair is provided to facilitate live recording and to program sound distribution throughout the Opera House. The two mics are sent to the local control room in each venue, where each channel is amplified using a Creative Audio MP405 remote-controlled preamp. Adjustments to gain, signal phase, phantom power, 20-B input pad and output mute are equally effected on both channels. The stereo audio pair emanating from the MP405 appears as two XLR connectors in the control room rack of each venue. A mono sum is generated and fed to the digital audio network via the local RAVE188 and on to the MediaMatrix.
Auditoriums are also equipped with a Creative Audio C141 Concert Com intercom unit and a 24-channel cue light controller. The cue light controller is controlled from the stage manager's desk node server and is controlled via one of its parallel input/output ports. The node server also controls the mic preamp and C141 ConcertCom via separate RS485 links.
Background audio levels for the auditoriums and foyer areas can also be adjusted using any of the 125 Creative Audio Speaker Volume Control (SVC1) panels located throughout the facility. The paging audio is constrained to a predetermined level regardless of the background audio level. The SVC1s vary levels by switching taps on the associated paging loudspeaker. The controllers are instructed to switch to a preset tap whenever a paging announcement is issued to the associated loudspeaker zone. The volume controls are addressable devices, which are set via DIP switches on the device itself.
Special mics are used to pick up and monitor ambient noise levels in the foyer areas of the Opera House. These Ambient Noise Level Sensing (ANLS) mics are preamplified at the source as part of the Creative Audio RMM1 remote monitoring mic unit(s). The RMM1 produces one compressed and one uncompressed line level output for the monitoring and ANLS mics, respectively. These outputs are then fed directly to the audio network via the nearest RAVE188.
The MediaMatrix server also oversees the operation of the DMS121 digital message store system. The server can detect paging activity in various zones, as well as store and play announcements at designated times. The server also gathers status information on power supply levels and amplifier monitoring and broadcasts any discovered faults to the production office.
Paging stations set up throughout the Opera House are the secondary source of audio for the paging system. The stations provide access to the system from areas not serviced by a stage manager desk. From any paging station, the user can select from four groups of destination paging zones. Stations are linked to the closest venue server data network via RS-485 connections. Paging requests and engaged zone group information are transferred via the RS-485 link. A single audio output carrying paging audio is provided at each station.
Other network-controlled devices
A host of other A-V devices are linked to the digital data distribution network. Control panels in various foyers throughout the Opera House complex allow an operator to alter the audio source for local paging zones, vary background audio levels and enable a local mixer. Control information is sent via an RS-485 link to the nearest data network node. The local mixers provide four audio inputs to a single audio output. The output is connected to the nearest RAVE188 input device where it is then carried to the MediaMatrix for switching.
Two Adaptive Micro Systems 32×128 pixel, tri-color LED displays are installed in an artists' lounge known as the Green Room. The displays provide visual indication of the paging sources for the Green Room zone. Control of these displays are via dual RS-485 links, one per display. The RS-485 interface adapters are housed in the nearby production office file server.
Remote loudspeaker level controllers located in every room are also serviced by the paging system. These controllers are attached in parallel across the balanced RS-485 feed and accessed individually using a predefined address. Multiple networks, and hence multiple RS485 adapters, are used to cover the entire complex.
Local mixers are provided at locations throughout the SOH. The mixers provide four audio inputs to a single audio output. The output is connected to the nearest RAVE188 where it is then carried to the MediaMatrix system for switching. The RMM1 Remote Monitor Microphone is used to permit both remote audible monitoring of sound in a given area and/or for use as the sense transducer for ambient noise level control equipment. Two outputs are provided from the unit. These are connected separately to the nearest RAVE188 CobraNet input device for distribution over the digital audio network.
Eight outlying node racks located throughout the the Sydney Opera House include a receiving RAVE188 unit, which is capable of handling up to eight analog inputs and output
Conclusion
The SOH paging and communications system demonstrates how a fiber-based network using standard, affordable computer networking devices can effectively transmit multiple channels of audio throughout a complex venue. Long distances no longer have to require an expensive, inflexible copper cabling infrastructure. RAVE-based networks solve those problems by routing dozens of channels of digital audio—free from EMI and ground loops—over distances of up to two kilometers. As illustrated in the Sydney Opera House, digital audio networks are proving to be a viable system solution for today's systems contractors.
"The Sydney Opera House paging system is a landmark project for our company in terms of both the profile of the building and the technology involved in the solution,"said Dodds. "We are very pleased with the results, and we look forward to applying our expertise to other venues with similar complex requirements, both in Australia and overseas."
Buttner is president of Aarvak marketing Communications, Novato, CA. Schwartz is a consultant with Peak Audio.
S&VC Online Sydney Opera House
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