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Distributed PA On A Fiber Backbone
Australia's Olympic Park, home to the 2000 Summer Games, showcases the future applications of large-scale distributed systems over a fiber optic backbone.
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With the software interface, system operators choose which of these inputs are active, for example, Local Input Node 12 to be active to “x” system zones. When the assignment is made, the software communicates with the CobraNet devices in the designated node, and they provide the commanded routing. “Quite likely, this is the first time that this capability has been done, in CobraNet terms,” he says. “Up to now, everything has been static. But now it’s flexible and dynamic in terms of routing, and this is just the tip of the iceberg, with more to come soon.”

The PA People are currently working on projects incorporating similar capability and more. Dodds conjectures that continued progress could potentially eliminate the need for hardware-based routing and matrixing, to be replaced by an actual on-network matrix utilizing CobraNet.

Analog audio inputs and outputs in the HBOC area are handled by both 8channel and 16 channel CobraNet Audio Bridge (CAB) units from Peavey, while I/O in selected venues use Rave 88 units from QSC. All audio interfaces to the MediaMatrix employs CobraNet, via Peavey’s CobraNet DSP cards.

Distribution & Routing
Distribution around the campus to each node is accomplished via an existing fiber network, which utilizes 3Com 3300 (http://www.3com.com) Superstack network switching. The PA People chose to continue the use of the 3Com equipment for the new CobraNet sound system implementation. (There were 21 nodes for the full-blown Olympic system, with about 24 in the final implementation including feeds to and from venues and other facilities). Separate Virtual Private Networks (VPNs) were implemented across the same physical link to separate CobraNet audio data from control system data.

In the computer room a set of three Superstack switches was implemented with a 3Com ‘matrix module’ backbone between them (two 8-port 100baseFX Fiber switches for the feeds to the nodes and a 24-port 100BaseTX switch for the local equipment). This was then linked to the actual HBOC area (where the operators sit) via a Gigabit fiber link and a second 24-port 100BaseTX switch. At each of the nodes there are 12-port 100BaseTX switches fitted with dual 100BaseFX fiber modules.

Node Electronics and Speakers
Each node houses a 3Com switch and up to six Crown CT- and MA-Series amplifiers each outfitted with the proprietary Creative Audio CobraNet USP/CN amp module. From there, the amplifiers deliver the assigned audio programming to loudspeakers mounted on poles, the majority being weatherproofed JBL Control 28T60’s, with JBL Marquis MS105’s, also weatherproofed, used to cover larger areas. Design of this specific facet of the project fell under the direction of Glenn Leembruggen of ARUP Acoustics, who undertook significant analysis and came up with an electro-acoustic solution that provides hi-fi like reproduction throughout the campus. (A significant quantity of amplifiers and loudspeakers, in addition to extra nodes, were added to the network on a rental basis for coverage to areas such as the Expo during the Olympic Games.)

The Creative Audio CobraNet amp modules also offered additional functionality that proved quite valuable. The modules feature two inputs that may be used to place signals on the CobraNet network. Remote source devices, such as Shure (http://www.shure.com) U4D wireless microphone receivers, can access these inputs via XLR connectors at every node. The inputs also serve as ports for introducing other remote sources onto the network.. As an example, several locations have been outfitted with ambient level control noise sensing microphones that access the MediaMatrix via the amp module inputs and the CobraNet network.

“All nodes also include an Ethernet access point which enables laptop computers to be plugged in for system configuration and control,” Dodds adds. “In such a widespread system, this can be invaluable in terms of convenience, time savings and real-time optimization of any node.”


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