Lateral Section

Scale (Feet)

A canopy built above the platform housing the loudspeakers, video screens, and lighting instruments is the best choice. Since religious services can reach levels of 95 dBA or more, the sound system is large and requires a steel structure to provide support and access to the clusters. Amplifier racks should be located close to the loudspeakers to reduce the amount of heavy-gauge wire needed to be pulled. Ample power can be made available from nearby electrical rooms. Local step-down transformers must be vibrationally and acoustically isolated. In very large congregations (6,000 to 10,000 seats) multiple rings of loudspeakers are required to cover the whole seating area. Since clusters are more than 25 feet in the air, localizing loudspeakers around the platform are necessary to pull the image down. These can be built into the step riser using small horn or cone loudspeakers. Full-range loudspeakers are not necessary to give the illusion of direction, but the first-arriving sound must be within 10 to 12 dB of the cluster level.

A design sketch of the West Angeles Church, a large Pentecostal church in Los Angeles, is shown in Fig. 20.12. Seating 5000, its floor plan is fan-shaped with 60% of the seats in the balcony, including the long slanted areas along the side walls. The fan angle is 154°, but even at this angle there is some shielding of sight lines to choir area at the rear of the platform.

Figure 20.12 West Angeles Cathedral, Los Angeles, CA, USA

(Acoustician: Marshall Long Acoustics; Architect: Langdon and Wilson)

Figure 20.12 West Angeles Cathedral, Los Angeles, CA, USA

(Acoustician: Marshall Long Acoustics; Architect: Langdon and Wilson)

The front of the platform that projects out from the front wall, is clearly visible, and can support a wide variety of performances. A canopy was designed to house the loudspeaker clusters, rear-projection video screens, and lighting fixtures, making for easy access and good coverage angles. Lighting catwalks ring the ceiling and help define its shape. The sharply defined corner of the ceiling in front of each catwalk keeps the theatrical lighting from shining on the video screens—an important concern in spaces with live TV coverage, where light levels must be kept high. The underside of the canopy is about 23 feet (7 m) high. This is high enough to get a sense of space above the platform but low enough to provide good acoustical support for the choir. The underside of the canopy is diffusive to avoid an echo return from overhead. Unfortunately the canopy was eliminated by the client in the final design.

Dedicated audio and lighting control positions are located in an open mix booth on the front edge of the balcony with an enclosed equipment booth behind. The patchbays and outboard equipment racks are in back of the mixer position. The wall above these low racks is glazed, allowing the technical director (TD) a clear view of the platform from within an acoustically isolated space. Since the congregation must be able to see over the booth, its ceiling is slanted down toward the platform. Video switching for the projection screens occurs just behind the TD position. Mixing for audio and video recording takes place in a separate studio. Audio and video recordings of the service are made available as part of the outreach ministry.

Large churches such as this one are totally dependent on electronic technology to distribute their message. Visual contact with the minister is enhanced through live television pickup of the service and projection on large video screens. Multiple video screens located in a canopy are ideal since they can be located between the loudspeaker clusters, giving good sight lines to most congregants. Screens located on either side of the choir are also a feasible alternative, however the seating fan angle has to be lower than about 130° for this to work well. Rear-projection screens are preferred to front-projection screens, since they can be angled down and they do not wash out under high background-light levels.

Synagogues

A synagogue is designed acoustically like other religious spaces emphasizing speech. Music is sung by a cantor, who is sometimes electronically reinforced but often not. There is usually a social hall adjacent to the sanctuary, separated by large doors or moveable partitions, which can be opened to combine the spaces. The social hall can serve as an extension of the main sanctuary during holidays so the audio systems must be linked. Social halls are designed primarily for speech intelligibility. Occasionally churches and synagogues will share a facility, which is used as a synagogue on Friday and Saturday and a church on Sunday, so the room must accommodate the needs of both congregations.

Orthodox synagogues have separate seating areas for men and women, divided by a freestanding wall or curtain. Orthodox Jews are proscribed from working and from doing a number of other things on the Sabbath, beginning Friday night at sundown and continuing until sundown Saturday. There is, for example, a prohibition against the lighting or extinguishing of fire, although an existing fire may be used for cooking. This teaching affects the use of electronic sound reinforcement. Each local rabbi makes his own decision on the exact interpretation and some congregations prohibit amplified sound, where there is a voltage zero crossing that is considered a lighting (or extinguishing) of fire. Others forbid the use of a dynamic microphone that initially creates the positive and negative voltage, but allow capacitive microphones because they modulate a DC voltage by varying the capacitance.

In the case of a prohibition of a zero crossing, a battery can create a voltage offset. This reduces the power output of the amplifier since the signal can only swing from zero to the positive rail, but the design complies with the teaching. David Klepper (1999) has written an interesting article on the subject.

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