Increasing liveness and clarity in a multipurpose civic center

Abstract

The Des Moines Civic center recently underwent a renovation primarily for symphonic uses, to improve hearing conditions on stage and in the house. This renovation included a new movable orchestra shell, rebuilt rear wall, and new finishes at sidewalls. The original shell did not adequately support bass or project sound to the audience, and musicians reported communication problems on stage. The rear wall was typically covered by a curtain, and returned confusing echoes when the curtain was withdrawn. The most unusual aspect of the room was the design of its sidewalls, broken into convex, down-leaning pylons, a signature of Paul Veneklasen, the original acoustician. KA analyzed the reflection pattern off the side walls and devised a treatment that maintained the beneficial aspects of the original design while dramatically improving clarity and presence. This paper focuses on the testing and modeling methods used to confirm our hypotheses about the problems caused by side wall reflections; the selection of appropriate materials based on in situ measurements and subjective listening; and architectural coordination.