The Buzz: Installation Spotlight: The Sound of Green
May 11, 2009 12:00 PM, By Jessaca Gutierrez
Point Park University, Pittsburgh
Localized control may seem counterintuitive in an age where having one control sweet spot provides facility AV managers with an efficient way to monitor and control equipment. However, in this design, the Renkus-Heinz CF121-5B powered loudspeakers also used less conduit. With a control room, all the studios would have been wired back to this room, requiring a large amount of conduit to be snaked throughout the building. To overcome resistance and signal degradation, a heavy-gauge signal wire going from the loudspeakers to the control room would have been necessary. In addition, a dedicated supplemental cooling system would need to be installed in the control room.
"One of our biggest challenges in terms of the wiring was dealing with the damping factor for the subwoofers that in some cases were 100ft. or more away from the amplifiers. We were never really comfortable with that," Nash says. "By going to the localized sound systems, we were able to eliminate all conduit except for stub-ups in the walls. We used plenum-rated cables instead of conduit-based. We were very pleased that the Renkus-Heinz loudspeakers and Bag End subwoofers both had onboard amplifiers that were rated for greater than 80 percent efficiency and emitted practically no heat."
Because the heat load from the new design was smaller, no supplemental cooling system was necessary, decreasing energy usage. The cabling wire was also able to drop from 6-gauge to 22-gauge wire that would run a short distance from the rolling rack in each studio to the loudspeakers. Having nearly eliminated conduit, the team used multiconductor MC cables to distribute the power branch circuits from the LynTec motorized sequencing panel that allows the sound systems in the studios to be turned off remotely in the event of a fire alarm. In this way, the team saved on materials and labor.
"When you're running conduit, you have to be very aware of how many bends you put in the conduit before you place a pull box or a junction box," Nash says. "It's a lot of fittings and a lot of custom-bending. The advantage of the multiconductor MC cable is that we were able to specify that cable to come preloaded with the desired number of circuits with isolated ground. The electrician never has to worry about bending radii or junction boxes. The conductors are already in the metal casing."
To make sure the four loudspeakers provided the best coverage, the team plotted the spherical expansion of the acoustic pressure waves and positioned the loudspeakers in each studio. This is a departure from the historical approach of two loudspeakers situated at the front of the class, with students and faculty in front exposed to sound in excess of 85dB—which poses health risks such as hearing loss, laryngitis, and even vocal nodules and polyps—and students in back either pleased with the level or struggling to hear.
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