St. Johns College is one of Johannesburg’s oldest and most prestigious schools, with buildings and facilities designed by Sir Herbert Baker that are approaching their 100-year monument status. The institution has a strong tradition of feeding leaders into South African society and life at the school revolves around an Anglican ethos with masses and ceremonies held in the school chapel daily. The schools preferred Audio and Worship Install Specialist, Rob Mills, approached the Audiosure team to assist with designing and augmenting the sound in the chapel. “They can’t hear me in the back, can you fix it?” was the challenge to be overcome for this installation.
The existing system compromised a simple powered mixer driving two conventional horn loaded PA speakers. “Chapels or churches, especially traditional structures, are notoriously difficult spaces for sound reinforcement because they are typically highly reverberant and full of nooks and crannies. In this case, a long narrow space with a choir gallery, side chapel and sanctuary,” said Mills.
The new speaker system installed comprises of the Martin Audio O-Line 8 element array supplemented by a Martin Audio CDD10 differential dispersion center fill, with smaller fills in the sanctuary and side chapel. The differential dispersion unit works very effectively, covering the benches almost directly beneath it up to around 12m away. “Thereafter, the O-Line comes in, reaching the farthest recesses at the back of the space and the choir gallery. Both units are unobtrusively positioned with the CDD10 hardly noticeable in the woodwork and the O-Line array, which is surprisingly small, nestled against a side wall,” said Mills.
What makes the O-Line so unique for this kind of installation is that its vertical beam-forwarding is achieved by physically articulating the individual array modules to curve the array. To conform to each individual venue’s design, the actual array configuration is determined by Martin Audio’s powerful, optimization software called DISPLAY3.0. This software makes intelligent judgements and accurate calculations about the effectiveness of the array’s SPL and EQ distribution against objective target functions in the space.
The system is driven by an Allen & Heath Qu-Pac Digital Mixer feeding a combination of line, wireless and wired microphone inputs to five separately equalized and delayed outputs. The Qu-Pac allows for very precise equalization, delay and separate mixes to the main line array and fills. The result is a remarkably consistent coverage of every nook and cranny of the space, including an external overflow venue.
Martin Audio distributor in South Africa and system designers Audiosure, were not surprised by the effectiveness of the O-Line. Martin Audio Product Specialist at Audiosure, had the following to say “…it immediately solved various obstacles right from the inception. Maintaining historic aesthetics and not compromising the center crucifix was a high priority. This forced the main speaker system to assume an asymmetrical position. O-Line handled this brilliantly while still providing accurate imaging to the pulpit and a high degree of speech intelligibility,” he said. “The range ratio from the closest seat to the furthest seat in the balcony demanded that the system not load the double volume space other than the seating areas. O-Line is very well behaved in its mechanical steering capabilities and the software predictions made this very simple to calculate.”
The combination of carefully matched speakers and astutely equalized and delayed feeds to them makes for good localization of sound sources referenced to the main pulpit and sanctuary area, according to Mills. “In short, this project achieved the objective of making the spoken word as well as musical performance clearly audible without drawing attention to the technology. It is simply and almost magically intelligible and often hardly noticeable as amplified sound. This is largely attributed to the remarkably effective combination of differential dispersion and line array technology,” said Mills.
The Martin Audio Range of Loudspeakers, Line Array, Digital Amplifiers and Speaker Management systems provide world-class audio solutions to some of the most prestigious venues, house of worship, festivals, and nightclubs around the world.