Sydney Olympics 2

New Olympic Stadium Audio System Runs Via Ethernet

By Julius Grafton
Connections, Apr. 2000

Two world firsts:

One, the Stadium for next years Olympics is ready now.
Two, the audio runs wholly on Peavey CobraNet.

It's a sound system of Olympic proportions, the largest public address system yet installed in Australia, and it features world beating unique control technology. The system at Stadium Australia is operational and has just been tested on 104,800 people.

It worked superbly.

Stadium Australia was built in record time, and is the primary venue for the 2000 Olympics, to be held at a massive new site at Homebush - at the western head of Sydney harbour.

The story starts with a tender won by Sydney firm, The PA People, and its manufacturing arm Creative Audio, both headed by Chris Dodds. The original tender was varied when Dodds proposed an alternate system which offered both better features and a significant saving to the original specification. The PA People went on to prove to the consultants and the builders that the alternate system would do everything they required.

Now, after 12 months on site, and with over 70 kilometres of speaker cables run, The PA People have delivered the system and defeated the rumours that it wouldn't or couldn't work. If anything, the test was as tough as they come, and came just after commissioning the system. It's a test I wouldn't like so soon after I'd finished configuring a system - because it put the system to absolute limits.

The Mother of All Tests

The Mother of All TestsThat uniquely weird sporting fixture known as a Rugby League match was to be the first function at Stadium Australia. As a season opener, the organisers scheduled a double header on a Saturday afternoon in languid March. They expected 50,000 - a comfortable number. They sold 104,800 tickets and knew they had a full scale test of the entire site infrastructure on their hands.

Would all the toilets, flushing at once, overload the pipes?

Would 700 kegs of beer all feed at the same time the vast number of bars?

Would crowd control and public transport all work?

Crucially for Dodds and his team, the event became even more major as entertainment acts were added, and it became apparent the system would be totally utilised.

At the opening event, major musical acts used the system in between the matches. The crowd raised the noise floor as high as it could go, as the players rallied to the spectacle and the vibe of The Huge Crowd. The weather was hot too, which provided an ideal test environment.

The System

The most obvious thing about the system is the largest part - the distributed PA in the arena. Clusters of speakers are logically placed high with sound directed down to the audience, all 110,000 seats.

It must deliver105 dB SPL by specification- which it now exceeds. The delivered sound is full frequency - there are bass cabinets flown in all the major speaker clusters. On opening nights it produced full fidelity, broad band sound reinforcement - which is beyond what many arena audio systems will do. Often they are designed for vocal/voice projection - from 250Hz to 6kHz - only.

Speaker placement anywhere in an architectural form is crucial to avoid reflections - slap back, or echo. If you put a central cluster of speakers above the exact centre of the field, arrayed 360º to reach every seat, it could be unintelligible due to echo back off the seating area. It'd also be impossible to hang, unless you had a skyhook.

The next design approach could be some clusters around the place, pointed at each stand. These would interfere with each other as the sound from one would reach a seat at a different time delay to one placed elsewhere.

This project benefited from logical design by the consultant, Andrew Prager of Flack and Kurtz, in New York city. The consultants role is to maximise the result and to minimise the budget. Hire a good architect next time you renovate your house, and they will save you more than their fee.

The system entails a variety of speaker clusters. There are 20 clusters of speakers rigged under the roof of the main east and west stands, with numerous supplementary speakers underneath the lower grandstand roof and in places where needed.

There are clusters located on the temporary end stand lighting towers, to deal with the two huge temporary stands. These stands will be removed after the Olympics.

Finally, there are speakers distributed on the underside of various stands and in places some fill is required.

The whole philosophy is to direct sound into discrete seating areas with minimal overlap - minimising any echo and keeping time alignment correct.


Enlarge View

There are Four amplifier rooms, and the longest speaker run from these to the most remote cluster is a massive 420 metres. To avoid line loss which happens with all cable, 8mm speaker cable is used (this is rated at 70 amps) which is big cable. This length of speaker cable presents around 1dB line loss with an 8ohm load, according to Dodds. "The impedance goes up, it's the impedance of the cable compared with the impedance of the load that's important - the absolute impedance isn't the issue. The whole design calls for less than 1dB of loss on any one cable".

"For example, if there's two cabinets wired back to one amplifier channel, then there's two cables (back to the amp). If there was one cable, you'd get twice the loss".

The amplifiers used are all made by Crown - 94 MA series for FOH duties, and 56 CT series for BOH - spread equally around four amplifier rooms.

The Speaker System

It's all made by Bose. Originally the specification called for EAW, which is the type that was tendered by all bidders. The P.A. People also submitted an alternate tender, worth about $3.5 million - as much as half the total of some tenders.

To prove that the alternative would work, BOSE provided Modeller and Auditioner analysis to actually demonstrate what a given output from the entire system would sound like in a particular location in the stadium. This acoustic modelling requires the parameters of the venue be loaded into a PC, and a whole lot of number crunching (in Modeller) and auralisation (in Auditioner) later, a given `sound' can be heard on the calibrated Auditioner listening station .

The modelling of the potential results of the alternative PA People tender proved to the consultants and the builders that a BOSE alternative would match or exceed the specification. The reaction in the trade was fairly loud, `how can this be?' was a common refrain heard here at the Connections Cottage, some ten miles from the Stadium!

Panaray LT cabinets are used in all the main clusters, these are a 2 way weatherproof horn loaded mid/high cabinet, and they are supplemented with Bose 502 BE bass enclosures.

The main cabinets, Panaray LT 3202, 4402 and 9702, are all similar - they are loaded with the equivalent of one or two 10" drivers and one high frequency compression driver. The model numbers denote different dispersion. The 3202, for example, has a breathtakingly narrow dispersion of 27º horizontal by 20º vertical.

The PA is an active 3 way system.

"This alternative system differs in terms of certainty of performance" says Dodds, "and this was finally proven this week (at the opening). We knew what it was going to sound like, thanks to the Auditioner process".

Control

The control system as supplied bears great similarity in its functionality to the one originally specified by the consultant, Andrew Prager.

But it is an alternative.

"We came back with a fully conforming tender, and an alternative speaker system and an alternative control system. The acceptance was based on the alternative speaker system - and during the period of the contract they choose to move to the alternative control system. The original specification called for an IED control system" says Dodds.

"A lot of the control system is our intellectual property, it is based on two third party products, the first being Peavey Media Matrix with Cobranet. This is the first MediaMatrix installation using Cobranet in the world. The control you can acheive with Media Matrix are astounding"

"The second half of the control system, and just as exciting, is Crown IQ - with the new USP series modules which Crown are about to release, and a new card we developed with Crown which makes them the first amplifier manufacturer to be CobraNet compatible".

CobraNet is a technology owned by an American firm called Peak Technologies [now Cirrus Logic]. It allows real time transmission of 64 channels of full bandwidth audio on Category 5 Ethernet cable. A 100 Base T Ethernet system, it is recommended that only CobraNet be run on any one network. This kind of network is what we have here in the cottage, with blue multi strand cable and RJ-45 connectors on the walls.

It's not dissimilar to your average office Ethernet network, which runs 10 Base T - just faster.

Each Ethernet point runs back to a switch or hub, effectively a node point. In the case of Stadium Australia, and indeed any network covering a lot of floor space, you need to use Fibre Optic cable and transceivers - instead of plain old Category 5 cable.

The wild and exotic aspect of CobraNet is that with one cheap and simple Cat 5 cable you can carry 64 balanced audio lines! Try doing that with analogue cable - you'd have a multicore of about 40mm outside diameter, and almost a week in labour to terminate each end with 64 XLR connectors.

These days almost every electrical contractor knows almost enough to be dangerous, and even Todd, our honest but slightly slow electrician here at The Cottage can run Category 5 cable - and almost terminate it properly. It's easy.

So where did CobraNet come from?

Remember Lone Wolf and Media Link - that radical new technology first almost seen at ENTECH 1994? That's right, the demo crashed, and so did the company. But it was a portent of things to come. And it has little to do with CobraNet except for the concept.

Peak Audio [now Cirrus Logic] invented and licensed CobraNet to various pro audio manufacturers, and QSC were first to market with RAVE - which stands for Routing Audio Via Ethernet. This was shown at ENTECH last year, and features in another PA People installation, one just completed at the Sydney Opera House.

The RAVE implementation of CobraNet is a simple point to point method of shifting audio on cheap and easy cable. It also potentially allows a card to be inserted into a QSC amplifier, so that instead of running a balanced analogue audio line to the amp, you stuff an Ethernet cable into it instead. Major advantage: 64 discrete channels on one cable. Choose a channel address at the amp, and that's what it gets.

Possibly inflamed with the power this allows, Dodds and his team at Creative Audio set about engineering a CobraNet card which would fit into their favourite amplifier brand, Crown.

Crown of course own the IQ system, a proprietary method of monitoring and remote controlling a Crown amplifier.

Dodds figured Crown amps configured with CobraNet would/could be linked to Media Matrix, the Peavey digital audio control and processing system. Peavey probably think the same thing, and are doubtless developing CobraNet cards for their amps too.

At Stadium Australia are two CobraNet networks, one for inputs and one for outputs.

Software City

To control everything, the system uses a complex but effective overlay of three kinds of software. First in the chain is version 3 of Peavey's Media Matrix software - on Media Matrix hardware. This is an industrial strength PC with a central Media Matrix processor, and breakout boxes to handle the analogue audio where CobraNet devices (such as the amplifiers fitted with the new Creative Audio cards) are not used. In this case, this is the first time in the world that Peavey's new CobraNet Audio Bridge (CAB) have been used. This is a new development for Media Matrix, and allows remote deployment of breakout boxes, something that couldn't be readily done with the traditional MM BOB - Break Out Box.

Essentially, the CAB boxes are the interface between the Media Matrix fitted with CobraNet DSP cards and the analogue world. A CAB is required anywhere you want analogue audio - either inputs or outputs. Each CAB is configured for eight analogue audio inputs (CAB 8i) or eight analogue audio outputs (CAB 8o). Between each unit and the MediaMatrix, you run category 5 cable.

Crown IQ software is deployed to operate the amplifiers. Understand that Media Matrix operates in place of traditional analogue processing devices. Imagine you are at a mixing position. MM will do the EQ, delay, limiting and mixing role - then send to the amps as many audio outputs as you have hardware for. But down at the amps the volume of each, and the control parameter monitoring of the amplifiers and the speaker loads are all outside of Media Matrix. This is where Crown IQ comes in, it does these functions and provides two way control to a PC loaded with IQ software and IQ hardware.

But two disparate collections of software, no matter how contemporary, do not make an integrated system. This is where The PA People's Creative Audio software overlay kicks in. This is software run on a PC network which provides a graphical user interface upon which can be complex or simplified commands and functions for the customer to utilise. It seamlessly addresses IQ and Media Matrix.

"The way it works is as a client - server network with Media Matrix (V3) and Crown IQ (V4) as servers, and our software as a client. Our box runs our software, code named Creative Audio Stadium Control (CASC) on QNX and is a client of both. The user interface is on another layer, it's a PC running NT and all three systems (ours, MediaMatrix and IQ) are clients."

"Our overlay is the only thing the operator needs to use. The Opera House now use software based on the same core code modules. We can offer to integrate the `best of breed' software from any other manufacturer into our system".

"We believe our future is based on supplying solutions, in partnership with others. No one can do it alone. We can come up with a package that delivers what the client needs".

This control and monitoring of the system functions using CASC is done on a conventional (non audio dedicated) Ethernet network between the Operators PC (these can be located anywhere in the venue where there is an RJ-45 Ethernet socket) and the main control room computers - Media Matrix, IQ, and CASC. All these are double redundant - meaning there are two of them, and sitting on a hefty uninterruptable power supply.

If a PC dies, the audio path remains in place.

The CASC GUI can be set up any way required at an Operators PC. The demo I saw at the Stadium showed a graphic of the whole FOH or BOH systems, with presets for different modes of operation. These modes may involve a particular seating configuration in the stands. Each mode may require different system settings - for example, if the audio focus is to be at one end of the ground, then the time delay for every part of the system needs to radiate in a circle outwards from that very position.

The CASC system can recall a preset the underlying Media Matrix and IQ systems at the touch of a button on screen. The command is sent, Media Matrix and the IQ systems then re-calls every audio setting, equalisation, time delay, and limiting - at every amplifier channel.

If the system was to be of a traditional `analogue audio' type, then an enormous number of signal processors, equalisers, crossovers and line level cables with booster amplifiers would be needed. Even then, the ultimate conventional analogue audio system would be unable to be reset and repatched in anything approaching any less than a working day.

Tricky Bits: Behind The System

Peavey would probably say that Media Matrix alone could run the system at Stadium Australia - and in a less than basic sense it could. Media Matrix is a modular digital audio toolbox which does signal processing and mixing functions within a PC - saving patching and acres of rack space.

However the system requirement at Stadium Australia also calls for a phenomenal number of background (back of house, or BOH) speakers - 1,600 to be exact. These are all organised into zones, which can be isolated, and signal processed as required. A significant number of these have discrete audio control, such as in bars, restaurants and suites.

Then there are output splits from audio distribution amplifiers for various purposes at various places around the site, and an input from the Emergency Warning system.

But it's the functionality which makes this into the smartest PA south of the Equator. Example: a paging station. Creative Audio made these to suit the job. A staff person can plug one in somewhere suitable, and assume control of a part of all of, the PA. The microphone in a gooseneck is there for speaking into, obviously. But it's the preset buttons which are trick.

Because of the CASC overlay, the engineer or operator can assign one, several or endless numbers of prerecorded WAV files to one or any button on one or any paging station. A WAV file is a digital audio file, and typically is a noise, chime, or announcement. Hit a button, hear the announcement.

Media Matrix has a flash new feature in Version 3.0, called `Probe' - which allows you to monitor any stage of any signal path. These `Probe' outputs can be assigned to any function, anywhere in the system.

Outcome

The main audio control room is up on Level five of the Western Stand. It houses a mixing console (Soundcraft K3), effects, background music generating devices like cassette, CD and tuner, and all the networking equipment.

From here, the engineer or the operator (it may be the same person) can access via PC absolutely ANY part of the sound system in virtually any part of the complex. See on screen what any amplifier is doing. See or hear what signal is going where through the Media Matrix system.

Send different mixes of different things to different places around the largest public venue yet built anywhere in the region. Allow corporate box users to alter their volume or program. Give broadcasters the splits they need, where they need them.

This controllability and functionality is unparalleled, and allows the Stadium owners to schedule virtually any event into the place with certainty that audio is not a problem, now or in the future.

How good is it?

The Bee Gees used the Eastern Stand speaker clusters for delay speakers, secondary to their Meyer system at presstime.

About Peaveys CobraNet

The CAB8i (Peavey CobraNet Audio Bridge) has 8 inputs which are software selectable to be mic or line. Gain (before the A/D converter) can also be adjusted by software. In addition to the audio inputs, the CAB8i also has 8 n/o, n/c relays, 8 control inputs (for analogue pots, switches) and 8 control outputs (5v DC for triggering relays, LEDs etc). All of this travels down a single CAT-5 to the next device on the CobraNet network. The CAB8i has a single RJ45 port on the rear panel to connect to the CobraNet network. In addition, it also has two BNC connectors allowing a second (automatic swap-over) CAB to be connected for redundancy reasons.

The CAB8o is essentially an output (line level) version of the CAB8i. It also contains control ports, relays etc.

CobraNet uses Fast Ethernet (100 Base T) hardware, not 10 Base T.

The control network on MediaMatrix (using multiple, distributed PC's to control the system) can run on either 10 Base T or 100 Base T. The audio network however (CobraNet) must have its own dedicated 100 base T network.

The distance between CobraNet devices on the network is limited to 100m on CAT-5, or 2km on fibre (using Media converters at each end to convert from CAT-5 to multi-mode fibre and then back again). A network can have a combination of both fibre and CAT-5.

Each DSP card in the MediaMatrix can support 32 inputs and 32 outputs (or 4 x CAB8i and 4 x CAB8o). Basically, a single CAT-5 comes out of the DSP card (RJ45) and then runs to a Fast Ethernet hub. Each CAB device is then connected to the hub. In the stadium application, there are multiple DSP cards. Each card is essentially supporting it's own CobraNet network however all of these networks combine to become one back at the MediaMatrix.

Any combination of inputs can be routed to any combination of outputs.

CobraNet is not unique to Peavey - QSC's RAVE is an adaptation, and more implementations of CobraNet technology will arrive Real Soon Now!


The System Described

Speaker System

Arena Speakers, Type A

There are twenty type A clusters distributed along the main front gantry of the east and west stands. There are three sub types:

Type A clusters are located at positions A3 through A8. Each cluster comprises a steel frame loaded with a Bose LT3202 mid/high cabinet, a Bose LT4402 mid/high cabinet, a Bose LT9702 mid/high cabinet and four Bose 502BE bass cabinets.

Type A* clusters are located at positions A2 and A9. Each cluster comprises a steel frame loaded with two Bose LT4402 mid/high cabinets, a Bose LT9702 mid/high cabinet and four Bose 502BE bass cabinets.

Type A** clusters are located at positions A1 and A10. Each cluster comprises a single Bose LT9702 mid/high cabinet.The cluster is permanently mounted to the roof structure.

Type B clusters are located at positions B1 through B5. Each cluster comprises a steel frame loaded with a Bose LT9702 mid/high cabinet.

Type C speakers are located at positions C1 through C26. Each cluster comprises a Bose 502A full range cabinet fitted with a Bose CVT-5 constant voltage transformer. The clusters are permanently mounted to the underside of the Level 3 cantilever.

Type D clusters are located at position D1 and D2. Each cluster comprises four Bose LT3202 mid/high cabinets, two Bose LT9702 mid/high cabinet and a steel frame loaded with eight Bose 502BE bass cabinets. The clusters are permanently mounted to the temporary end stand lighting towers.

Type E/F speakers are located at positions E1 through E8 and F1 . Each cluster comprises a Bose 402E full range cabinet.

Back of House Speakers

There are four loudspeaker types employed in BOH areas. They are the Bose Model 8, Bose Model 25, Bose Model 32, and Bose Model 502A:

  • Model 8's are used in toilets and areas requiring low level
  • Model 25's are used on Level 1, 2, 4, and 6 in public areas
  • Model 32's in areas with ceilings requiring higher level
  • Model 502A's in high roof areas such as the Banquet Halls, main Foyers, and temporary end stands

Amplifiers, Signal Processing and Load Monitoring

Signal feeds from the sound control room to the amplifiers are via a fibre optic CobraNet distribution system.

Every amplifier in the system is fitted with a signal processing card with the following features:

  • eight bands of parametric EQ per channel
  • crossover
  • digital time delay
  • amplifier monitoring and control
  • preset configurations

Front of House MA Series Amplifiers fitted with USP2 Modules

There are 94 Crown MA series amplifiers fitted with Crown USP2 modules in the system. They are located in each of the four Amplifier Rooms. The USP2 modules provide all standard audio functions available from the current version of IQ for Windows and possible within MA series amplifiers including dynamics, equalisation and delay.

Control of the Modules is via CrownBus current loop derived from Creative Audio CNIQ1 CobraNet to CrownBus interfaces adjacent to the amplifiers

Front of House SLMB Load Monitoring

There are 24 Crown SLM8 Speaker Load Monitoring units in the system to monitor the FOH speakers. Six units are installed in each of the four Amplifier Rooms, adjacent to the amplifiers.

The SLM8s connect directly to the MA series amplifiers (audio load side) and to a CrownBus local to the room, to permit load monitoring and reporting.

Control of the SLM8s is via the CN-IQ unit connected to the local CrownBus. Audio from the SLM8 monitor bus is connected to the CN-IQ to permit remote audio monitoring of the MA series amplifiers via the CobraNet network.

Back of House CT Series Amplifiers fitted with USP2/CN Modules

There are 56 Crown CT series amplifiers fitted with Crown/Creative Audio USP2/CN modules in the system. They are located in each of the four Amplifier Rooms.

The USP2/CN modules provide all standard audio functions available from the current version of IQ for Windows including dynamics, equalisation and delay, load supervision, and CobraNet source and monitoring channel selection.

Control of the Modules is via the CobraNet network that delivers audio to the amplifier.

Crown IQ Bridge CN-IQ

The CN-IQ bridge translates control system data from CobraNet to Crown Current Loop format. This enables the control system to communicate with the amplifiers and other

Crown IQ components.

Peavey CAB8i CobraNet Audio Bridge

The Peavey CAB8i translates audio carried on the CobraNet back to analogue format for use by the FOH amplifiers and the hard of hearing systems.

There are two CAB8i units in each amp room.The `buddylink' system enables automatic changeover should one network or CAB8i device fail.

CobraNet Hubs and Patch Bay

There are two 24 port Fast Ethernet hubs each fitted with a Fibre Optic input, and an associated 24 port CobraNet patchbay in each amp room. These Hubs and patch bays represent the A (black) and B (yellow) CobraNet networks.

Peavey MediaMatrix

The system utilises two MM940 main frames with dual `hot swappable' power supplies, each fitted with four MM-DSP/CN processor cards.

The Media Matrix units are controlled from either the Operators GUI or the Engineering GUI, and also accept commands from the control system relating to the recall of presets and the routing of audio as requested by the paging system and paging stations. The MediaMatrix will also route audio to and from the .wav player for the replay of messages.


Enlarge View

Inputs to the MediaMatrix from the eastern stand are converted to CobraNet format in the Comms Rooms located on Level 1 South East, using Peavey CAB8i interface boxes. Inputs to the MediaMatrix from the western stand are converted to CobraNet format at the Control Room L5 West using Peavey CAB8i interface boxes. All Peavey CobraNet nodes are duplicated and wired in parallel using the sync detect feature to enable automatic changeover should one unit fail.

CobraNet Hubs and Patch Bay

CobraNet audio is distributed using standard Fast Ethernet hubs. There is one network connected to the Comms Room, and one Network Connected to the Amp Rooms. On the Comm's Room network, there are two 8 port Fast Ethernet hubs each fitted with a Fibre Optic input. On the Amp Room Network, there are two 8 port Fast Ethernet hubs, and two Fast Ethernet modular switches each fitted with four fibre ports and two copper ports.

There are also two 16 port CobraNet patch bays.

Fibre Patch Bay

There is a fibre patch bay located in the Sound Control room which terminates the fibre cable to/from the Comms Room and the four Amp Rooms. The fibre is then patched directly to the CobraNet Hub fibre inputs.

Networks

Networks comprising various serial configurations are used to interconnect controlling devices, interfaces and controlled devices. In some cases control data travels with audio data on the CobraNet Networks.

Network Elements are as follows:

CobraNet Network

These Ethernet networks carry both digital audio and IQ control data throughout the stadium. Dual networks provide fail-safe redundancy. These networks connect to the following:

  • Ethernet Hubs (Copper and Fibre)
  • All USP2/CN modules
  • All Creative Audio CNIQ1 CobraNet-CrownBus interfaces
  • All Creative Audio CN232 CobraNet to RS232 Interfaces
  • All MediaMatrix CobraNet ports
  • All Peavey CAB Analog Audio - CobraNet interfaces

10 BaseT TCP/IP Network

This Ethernet network is for transmission of data only chiefly within the Sound Control Room between Controlling Devices and interfaces.

RS485 Network

Four independent RS485 networks interconnect all devices with RS485 control requirements.

CrownBus Networks

Five local CrownBus networks link CrownBus devices within each Amplifier Room and the Sound Control Room. Each CrownBus network connect to the following:

  • Creative Audio CN-IQ1 CobraNet-CrownBus Interfaces
  • All Crown SLM8 Load Monitoring Units
  • All Crown USP2 amplifier modules

Local RS232 Interconnections

Local RS232 interconnections will be used in the Sound Control Room to link each MediaMatrix RS232 Port to the CobraNet networks (for Crown IQ server access to CobraNet), and to link each QNX RS232 port to the Remote Access Server