04.04.2002 01:28 PM
AUDIO FOR BROADCAST
The Sound of Hollywood
Dolby Laboratories relocated its Los Angeles office earlier this year to the heart of the Burbank media district-a move that reflects the company's commitment to the Hollywood entertainment community. The facility includes project, conference, and home theater rooms; event space; and a screening roomÑthe Larry Umlang Presentation Theatre II. As might be expected from a company with an increasing influence in television production and a major stake in motion picture audio, the 49-seat Theater II is a state-of-the-art screening room that incorporates the latest in equipment and acoustical design. It is named in honor of Dolby's original Hollywood theatrical engineer, who died in 1988.

David W. Gray, vice president for Dolby's Hollywood Film Division, said the theater's design was determined by the need to keep sound in and any airborne or structure-borne sound out. With its close proximity to the 134 Freeway, NBC-TV's helipad, and, most especially, Burbank Airport, isolation was certainly a challenge.

"When airplanes take off, they turn and end up over Studio City, with their rear ends directly facing our building, and give it the gun to get the last amount of lift," said Gray. "The first thing we did after we purchased the building was to take three days of measurements."

According to Gray, those figures, plus measurements taken by neighbor Warner Bros. during construction of its latest theater, combined with the knowledge that digital tracks can typically reach 105 dB and above, all determined the screening room's design. "It's completely floating and isolated," he said, noting that the room sits on two-and-a-half-inch Neoprene blocks. "Thicknesses of air gaps between the multiple walls were all determined based on the recordings," he said.

The screening room was designed by David Schwind of acoustic consultants Charles M. Salter & Associates, and Nick Ybarra and Max Williams of Rothenburg Sawasy Architects, the 1989 building's original designers; plus Dolby's Douglas Greenfield and Gray. It incorporates classic acoustic practices. "My theories tend more to the old-time," said Gray. "The design, in a nutshell, was based around the desire for a very quiet room with a slightly higher reverberation time than is normal for a room of that size. We really wanted to have the capability of being not only a screening room, but a presentation room as well." In addition, he noted, keeping the reverberation time up gives the feeling of a bigger room yet maintains speech intelligibility.

In the projection booth, TASCAM MMR-8s and DA-88s accommodate dual-system work in the digital domain, and a dual mag machine handles double-system mag, with a custom switcher and a small Yamaha digital console for mixing, testing, and checks, such as A/B comparisons between master MOs and prints. A Crestron system provides remote control of the equipment via Ethernet.

Although all of Dolby's current units are installed, the main screening room processor is the CP200. Dolby's oldest still-working processor at nearly 21 years old, the CP200 was chosen for its flexibility and handling of formats such as 70 mm. Gray reported that what little EQ is being introduced is handled in the digital domain by the parametrics in the BSS crossovers.

The front three channels comprise custom JBL three-way speaker assemblies that use design elements adapted from the cabinets installed at the previous Dolby screening room, as well as theaters at the Academy of Motion Picture Arts and Sciences and the Directors Guild of America. The close-coupled components utilize custom Neoprene gaskets and are sealed into a baffle wall that is specially constructed to tilt the components into the room at the correct angles and to minimize their distance from the microperf screen in order to reduce splash and high frequency roll-off.

For the three front channels, ported low-frequency cabinets, originally designed for the Academy of Motion Picture Arts and Sciences by JBL's Mark Gander and John Eargle, as well as by Greenfield and Gray, each house four 15-inch speakers in a diamond pattern, equidistantly spaced. Response is smooth, and according to Gray, there's virtually no lobing. A cluster of four 18-inch subwoofer speakers is positioned dead center, time-aligned to the center channel.

Multiple delay lines are also used to time-align the surrounds. "No matter where you sit, you've got surrounds that are blended together and in the correct time-alignment with the different screen channels," said Gray. "Pans work really, really well. It's not cheap, but, in my opinion, it's worth it." He also noted that Dolby took the opportunity to configure the room for future possible formats. The surrounds accommodate the three-channel rear of EX, and the room is wired for up to eight channels of surround. Additionally, two ceiling channels handle vertical height in a left-extra/right-extra configuration, "under the theory that," according to Gray, "it might be nice to get a mono image from the verticals, and if you're far-left and -right you'll never have a prayer." A center ceiling speaker was also installed.

"I'm personally convinced that four surround channels make a whole lot of sense," stated Gray. "The center is extremely effective. It's the same with the verticals. But the question is, in the average motion picture, how much can they be used?" Time will tell.


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