St. Charles Borromeo is a venerable Catholic church with a classic cruciform shape, 180 feet long by 45 feet wide by 40 feet high, seating 920 people. It serves a distinguished congregation including the Bob Hope family and Roger Mahoney, the former Bishop of the Diocese of Los Angeles. The church recently undertook a rehabilitation of the structure and interior. The architect was Dan White. The AV installation was by AMT Systems. The sound system and acoustical design were done by Marshall Long Acoustics.

There were several challenges associated with the project. A large dome over the front part of the church, including part of the sanctuary, is 42 feet in diameter and rises to a height of 68 feet above the floor at the top of the cupola. The interior of the dome was to be painted with decorative religious art depicting a fleecy clouded sky with biblical figures. The plaster needed to be smooth and was thus acoustically reflective. This made it difficult to control sound reflections from the dome. The solution was a directional line array speaker above the sanctuary combined with distributed overhead loudspeakers built into custom pendant light fixtures. The loudspeaker design was utilized to try to control sound so that it did not reflect from the dome back to the congregation or the sanctuary.

Another issue was that the sounds associated with the religious services originated in the sanctuary, while the choir was located at the rear of the church about 150 feet away. This caused time delays and led to the hanging light/loudspeaker solution. In the final design each hanging loudspeaker could be fed from microphones at opposite ends of the church and the overall delay times set depending on the source origination point. This proved to be quite successful except in the area near the sanctuary. Here a series of step speakers were included in the original design to cover the first few rows of pews. These were not installed and thus there is reduced intelligibility in this area.

The overall result is clear intelligibility throughout the transepts and most of the nave. Visually, the church is spectacular, with the painted figures and the beautiful light fixtures hanging above. The original reverberant space works well for choral music and for the pipe organ located at the rear of the choir loft.