Simon Fraser University
Simon Fraser University's Convocation Mall sound system was reaching the end of it's useful service lifetime and was in need of replacement. The original cluster was comprised of a single 15" horn loaded theatre speaker and two multicell horns and drivers; one 10 cell 90x40 horn and one 2 cell 40x20 horn. The original system had limited gain before feedback because of the location and configuration of the speaker systems. The audience for the graduating ceremonies has become much larger in the past 20 years, and that has increased the demands for greater depth of coverage in the mall seating area that the original sound system could not provide.
We elected to use a two cluster approach with a DSP audio processor to set equalization and delays for the front and delay clusters, plus the portable speakers that are used for stage monitors, walkway loudspeakers etc. The clusters are each equipped with two coaxial horn loudspeakers with a response down to 160Hz, plus a double 15" subwoofer for extended response for music playback. The lower horn is a wide angle device, and the upper horn is a narrower coverage device. The lower horn's response was shaded with the EQ in the DSP to adjust for response variation caused by coupling of the two horn mouths.
Cluster configuration front and side
The level, signal delays and equalization were set to provide uniform levels to the very back of the (295') 90m deep listening area. The signal delays for the second cluster provides for a seamless transition when walking from front to rear in the covered mall. The second cluster has the delays set to include additional delay time to take advantage of the Haas effect and maintain the image at the front cluster.
By reducing the levels needed from the front cluster and increasing directivity of the cluster, the gain before feedback was increased greatly, allowing a good safety margin when using lectern microphones and inexperienced talkers. The electronics and amplifiers were upgraded as part of this project as well.
We worked closely with the experienced Instructional Media Centre staff who did the system installation work and coordinated the cluster frame construction and hanging operation with SFU Plant Ops staff. This is an excellent example of a project where we are able to work with the in-house technical staff to augment their knowledge in a specialized area.