PEL Services Ltd Belvue Business Centre, Belvue Road, Northolt, Middlesex, UB5 5QQ

Phone: 020 8839 2100 E-mail: info@pel.co.uk www.pel.co.uk

Westfield Stratford City: Looks Great, Sounds Fantastic

An incredible 1.9 million square feet development

serving a catchment area of over 4 million people, the

£1.8 billion Westfield Stratford City retail project is the

largest urban shopping centre in Europe.

The development features 250 shops, 70 dining

facilities, three hotels, a casino, a cinema complex,

plus extensive office space, making it one of the

largest urban regeneration projects ever undertaken in

the UK.

The sheer scale of this retail development is like

nothing we have seen before and has required those

involved in its creation to use all their experience and

talent in their separate fields to bring the project to

fruition on time, to exacting standards and with a focus

on enhancing the consumer experience by the use of

technology.

The result is some very notable achievements

including one of the very best Public Address (PA) and

Voice Evacuation (VA) systems to be found in a retail

complex anywhere in the world. An exaggerated

statement to make? I don’t say this lightly, but when

you have manufacturers, consultants and architects

who have all been in the business for 20, 30, 40 years

or more making this same comment about the system

at Westfield Stratford City, it’s time to take note.

The clarity and quality of the sound produced by the

PA/VA system is exceptional, but what makes this all

the more impressive are the challenges faced and

overcome to reach that point, from the sheer size of

the retail development through to the combined

entertainment and security / safety requirements

placed on the system. To pull this one out of the bag

required a team effort by skilled partners.

PEL Services Ltd Belvue Business Centre, Belvue Road, Northolt, Middlesex, UB5 5QQ

Phone: 020 8839 2100 E-mail: info@pel.co.uk www.pel.co.uk

System Design

PEL Services - a leading UK systems company that

has been designing, supplying, installing,

commissioning and maintaining sound, fire, security &

communications systems for nearly 40 years - was

awarded the PA/VA contract from M&E contractor

Essex Services Group as a result of PEL’s extensive

experience and because of its ability to take full design

responsibility.

A development of this size and complexity requires

detailed acoustic modelling before any thought of

system design and equipment specification can be

entertained. AMS Acoustics had undertaken the

assignment at the previous Westfield project at White

City and Essex Services Group felt that it would be

appropriate to engage the services of this leading

acoustic consultancy to work jointly on the Stratford

City project, with AMS specifying the system

performance requirement and PEL determining the

constituents of the system and its configuration.

The first key stage of the process involved AMS taking

the architectural plans detailing building materials,

surface finishes etc. and, using proprietary and in-

house development design software, undertaking

acoustic modelling of the entire retail complex. Highly

knowledgeable in their field, AMS was quickly able to

identify six acoustic areas: two main areas (the

Northern Mall and Central Arcade) and smaller ones

such as lift lobbies and the welcome halls.

Loudspeakers were then entered into the software

programme to allow the computer to predict speech

intelligibility. This is performed by means of high

resolution ray tracing that systematically probes each

surface within the computer model which assimilates

the raw data required to fine tune the system and

acoustic properties in order to optimise the music and

speech reproduction. This laborious yet vital exercise

demands the enormous processing power of three 6

core computers, with each trace taking over two days

to generate the resultant data.

From here AMS was able to specify the Sound

Pressure Level (SPL) required and the speaker

placement, allowing AMS to confirm the suitability of

PEL’s loudspeaker selection and system architecture.

PEL is able to work with a number of PA/VA

manufacturers but with a system of this size and

complexity it was determined that only Bosch’s

Praesideo digital system running across a dedicated

fibre optic network was considered suitable for the task

at hand.

Unlike traditional PA systems, Praesideo uses a

network configuration rather than having all system

elements connected to a central controller. This

architecture gives real freedom in system design. The

'daisy-chain' network topology means system elements

can be connected to virtually any point and any type of

equipment to be located wherever most suitable in the

building (e.g. power amplifiers closer to loudspeakers).

What's more, by connecting the network ends together,

a 'redundant' loop is created so any break in the cable

doesn't affect operation - an important consideration in

an emergency system.

The Praesideo system was specified by PEL to drive

the top of the range Electro-Voice ZX1i full range

cabinet speakers for the main mall, with ceiling

speakers installed at the lower levels. Bosch modular

ceiling loudspeakers were used in the smaller locations

such as welcome halls and communal areas. Nearly

1500 loudspeakers were used in total, along with 45km

of cable, 21 equipment rack locations, 25 equipment

cabinets, each 36U (6’ high), and over 3 tonnes of

batteries for back up!

PEL Services Ltd Belvue Business Centre, Belvue Road, Northolt, Middlesex, UB5 5QQ

Phone: 020 8839 2100 E-mail: info@pel.co.uk www.pel.co.uk

PEL designed the system to be controlled from two

independent fire command centres via a multi zone

microphone console and GUI (Graphical User

Interface). The system is interfaced with a number of

‘packages’, including the fire detection system, the

centre’s own radio station and a special events

package.

Once specified, PEL produced system schematics and

calculated the amplifier (50935 watts in total) and

battery power required to maintain the system in the

event of mains failure. To replicate operating

conditions and thoroughly trial its performance the

entire system was then set up within an empty

warehouse rented by PEL for the exercise. It was then

witness tested by the client and the professional team

before handing over the detailed specification to Essex

Services Group for them to install the loudspeakers.

But that was far from the end of the story. Once

installed PEL carried out the commissioning of the

system and provided operator training.

A basic system was up and ready by February 2011 as

required and then developed as the centre was fitted

out.

Challenge Faced and Overcome

We have already seen the incredible scale of the PA/

VA system at Westfield Stratford City which brings

challenges in itself; but what about the other aspects

that have proved to be demanding? What about the

acoustically hostile environment a shopping centre

poses? And how do you get a system to perform to

satisfy two separate requirements that are almost

mutually exclusive?

All PA/VA systems in a retail environment are used

partly for ‘performance’ (music, messages etc.) but

with the emphasis understandably given to life safety,

i.e. voice evacuation. Invariably the ‘performance’, in

respect of clear, intelligible annunciation of the safety

messages, is compromised by the desire for good bass

response to satisfy the ‘entertainment’ quality. Clearly

Westfield Stratford City did not want safety

compromised under any circumstances but it did want

the performance aspect to play a far more eminent role

than is usual which PEL and AMS combined to achieve

very effectively.

The trick is to carefully balance the two. Whilst it is

exceptionally difficult to achieve, in the case of

Westfield Stratford City, the team effort between AMS,

PEL and Bosch, as well as the architects, won the day!

PEL Services Ltd Belvue Business Centre, Belvue Road, Northolt, Middlesex, UB5 5QQ

Phone: 020 8839 2100 E-mail: info@pel.co.uk www.pel.co.uk

If, at the early acoustic modelling stage, an equipment

based solution to audio intelligibility could not be found

AMS worked closely with the architects to solve the

problem, even advising on changing building materials

and to the extent of adapting the building design where

necessary.

AMS Acoustics refers to this aspect of a building’s

design as ‘Aural Aesthetics’. Modern architectural

design often focuses on open spaces and bringing light

into the building, using materials such as metals, glass,

and marble. However, these can cause rampant

acoustics – the sound literally bounces off the surfaces

and reverberates, making it difficult to communicate

and in the worst case making the space an unpleasant

place to be. AMS strives to work with architects to

harmonise the sensory elements and to make them

aware of the importance of aural aesthetics and its

impact.

At Westfield Stratford City a very good working

relationship was established with the architects who

were very receptive to AMS’s advice. In the top

Northern Mall, for example, the plan was to put the

speakers behind the ‘ribs’ in the ceiling, which

compromised the system performance, so discreet

insertions were made in the ribs for the speakers,

which overcame the problem. Additionally in the

Central Mall acoustic absorption material was added to

the ceiling to good effect without adversely affecting

the overall visual element.

The main malls also proved challenging given their

height and the number of levels encountered. The

danger posed here was incoherent sound merging

from these different levels, but PEL and AMS

overcame this with the clever use of delays. AMS

calculated the signal delay required and PEL set the

individual delays and EQ of each amplifier.

The success of this expertise and attention to detail

speaks for itself: the system proved so good that

Nicole Scherzinger’s performance at the official launch

opening ceremony was fed through the centre’s PA

system in preference to the dedicated performance

system hired specifically for her, as it was considered

superior. A remarkable achievement! Of course this

had the added benefit of allowing the singer to be

heard not only by the assembled dignitaries within a

localised area but to everyone throughout the centre.

The other main acoustic challenge faced at Westfield

Stratford City came from the exceptionally noisy giant

extractor fans that are used to remove smoke and

fumes in the event of a fire; a case of one life safety

device negatively affecting another, in this case the VA

system. With the higher than anticipated sound output

of the extractor fans it was evident that they would

drown out the VA system. The generally accepted

maximum SPL for noisy public areas is 90 dBA. But to

overcome the output generated by the fans, 93 dBA

was a critical requirement and hence the solution was

to go bigger and louder, with PEL using twice as many

amplifiers.

Experience Counts

The PA/VA system at Westfield Stratford City is a

testament to the quality of the equipment used and to

the expertise of those involved in the system design,

specification and installation. From the acoustic

modelling and speaker placement, to the equipment

specification and calculations and on through the

testing, commissioning and even the logistics involved

in such a large system, every part of the system design

has been pre planned and scrutinised to provide

Westfield with a PA/VA system to be genuinely proud

of.

If employing the skills and experience of industry

leading experts reflects the Westfield Group’s focus on

enhancing the customer experience then the technical

excellence of the PA/VA system can stand as a proud

testament to their wisdom.

Vic Swain, Engineering Director, PEL Services Ltd.