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Egyptian engineering

Egyptian engineering

Egyptian engineering

A beam-steering solution proved vital to ensuring intelligibility for Cathedral of the Nativity of Christ’s large congregation, discovers Simon Luckhurst

The construction of the new Administrative Capital some 40km outside of Cairo has led to the creation of many new and wonderful sites. When it comes to religious constructions, the majority of new buildings in the area are unsurprisingly mosques. The arrival, therefore, of a landmark new Christian place of worship gives the impressive building even greater focus.

Officially called the Cathedral of the Nativity of Christ, the huge domed building is set to be the largest church in the Middle East and was officially opened in the presence of Egyptian President Abdel Fatah al-Sisi and Pope Tawadros II. The new capital now shares the dual accolades of housing both the world’s biggest oriental orthodox church and mosque within its boundaries.

A Linea Focus DLI-430 cabinet
A Linea Focus DLI-430 cabinet

The vast site upon which the church sits was landscaped to include wide, open spaces and verdant greenery. It houses the cathedral, papal headquarters, a smaller church, a multistorey underground car park and a community service centre – all designed to be architecturally compatible with the cathedral. The design of the main building emulates Noah’s Ark, reflecting a Coptic tradition of the church as a lifeboat that transports believers to the safe harbour of eternal life. In addition to daily prayers, the Cathedral of the Nativity of Christ is used to host the most important events in the Christian calendar, such as Midnight Mass on Christmas Eve. Its high-profile services are regularly filmed and broadcast out to a wider audience. Sprawled over an area of 7,500m2, the building can hold up to 8,200 worshippers in total.

During the planning and simulation stages of the project, it was already apparent that the imposing building would create several challenges for systems integrator Audio Technology Egypt, which, having been invited to tender for the project, was tasked with managing sound reinforcement in the tricky space. Due to the cathedral’s huge dome, high vaulted ceiling and smooth walls and floors, the 135,000m3 interior has an extremely long reverberation time averaging 11s, making speech intelligibility for the congregation problematic. Additionally, the distance from the choir to the far end of the main nave spans more than 120m in length. For these reasons, Audio Technology favoured a beam-steering solution that could direct audio energy into the desired areas, selecting a Fohhn Linea Focus system. This latest generation of line source systems benefits from electronically steerable beam characteristics that are capable of creating direct and precise sound coverage, thereby aiding speech intelligibility by minimising unwanted reflections.

The large domes created issues for audio intelligibility
The large domes created issues for audio intelligibility

“Over the years, Audio Technology has supplied and installed sound reinforcement systems for numerous houses of worship,” explains Emad Adly, chairman of Audio Technology. “We also provided system calibration and design services for the Episcopate’s Saint Mark Cathedral, which led to us being invited to bid for the new capital’s Cathedral of the Nativity tender.

“This cathedral is very important to the president,” continues Adly. “He needs the very best quality and this was not easy in such a large place. We presented our technical offer together with the acoustic study of our design.

The acoustics of the cathedral were extremely challenging, so we had to get the best sound intelligibility results and also respect the speaker position with the Coptic altar design. The technology of array steering in order to cover the large area, especially the front section, which was around 60m, was vital.”

The Audio Technology team deployed 14 Linea Focus systems in total, with two lines of seven DLI-430 installed along the sides of the sanctuary to serve as the main PA system. These line source systems – which are over 4m in length – have been specially developed for long-reach applications. Two further DLI-430 cover the choir area. Along the nave, eight Fohhn DLI-230 cabinets form four delay lines, while two additional DLI-230 reinforce both side aisles. AFMG’s EASE Focus acoustic simulation was used to determine the ideal positions. “A lot of details in the design of the church had to be studied and simulated before installation,” says Adly. “It took us two months of hard work and several EASE modelling revisions.” Once the design was complete, the installation, commissioning and tuning took the team approximately one month

The Audio Technology team
The Audio Technology team

A 48-channel Soundcraft Vi1 console with CSB 32/8+8 compact stagebox has been integrated to handle audio mixing duties. This takes inputs from a CD player and a selection of wired and wireless microphones from Shure that include SM series wired mics, MX400 gooseneck microphones and a Shure SLX wireless system with a UA844+SWB-E antenna distribution system, before being fed through the Fohhn Master AM-40 AIREA intelligent audio processor and passed off via Cat cabling to the column speakers. The AIREA can accept signals from a variety of sources and delivers that signal plus control and power out to the cabinets, which all receive their own individually controllable and processable signals.

A selection of JBL CBT Series passive, controlled-coverage columns provide reinforcement in out-of-the-way areas not fully covered by the main Focus cabinets, in addition to the smaller chapel, auditorium and multipurpose hall. These are all powered by CDi DriveCore amplifiers from Crown.

Peripheral areas are covered by JBL column speakers
Peripheral areas are covered by JBL column speakers

“From the front to the back of the sanctuary, the sound inside the cathedral now is just fantastic,” comments a representative from the cathedral. “It’s not a very easy space to manage, acoustically, but everyone coming here is very happy with the quality. Audio Technology have also been very polite and cooperative. If we needed anything from them, they would immediately get it completed.”

“Covering this big space with only 14 digitally steerable line array units was no simple task; however, the measured Speech Transmission Index (STI) with the new system achieves on average a reading of 0.6,” concludes Adly. “The comments from the team there are that the cathedral has the best sound quality in Egypt. Since it’s opened, the president has also issued an order to build the biggest mosque in the Middle East stating that, ‘I need a clear sound just like we have at the cathedral’. There’s no better commendation than that.



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