A key component of the restoration is a complete reworking of the Cathedral's audio distribution system. To this end the services of Acoustic Directions' principal acoustics consultant Glenn Leembruggen were engaged. His brief was to design and commission a modern and effective audio system which would enable the Cathedral to more effectively conduct its ministry and communicate with the congregation.
Leembruggen is a pioneer in the use of beam steered line arrays and knew that this technology would be the best solution for the problems associated with long reverb times and multi-path reflections which are evident in the Cathedral.
The specification called for 46x Acoustic Technologies ALA07C Beam Steered Line Arrays to be mounted on the Cathedral's columns. The mounting height on the columns varied with location, requiring steering angles from 20° to 40°. A custom frequency shaded tweeter array with adjustable inclination angle was designed and supplied for this installation.
Beam steered arrays require separate DSP and amplification for every transducer in the array. The St Paul's installation saw the debut of the Acoustic Technologies FLA8.dsp Focused Linear Array System processor/amplifier.
The FLA8.dsp is an eight channel amplifier delivering 40 Watts per channel with extensive on board DSP capabilities. The St Paul's Cathedral installation required some 26x FLA8.dsp with many of the ALA07C's being powered in parallel due to the symmetry of the cabinet placement. Overall system integration is provided by Biamp Audia digital controllers programmed to provide a simple to operate system, catering for the daily needs of the church.
(Jim Evans)
