Audio in the Citi

The New York Mets' new Citi Field showcases recent advances in loudspeaker design, DSP, and monitoring/control. 6/22/2009 12:24 PM Eastern

Audio in the Citi

Jun 22, 2009 4:24 PM, By Trevor Boyer

The New York Mets' new Citi Field showcases recent advances in loudspeaker design, DSP, and monitoring/control.

This April, as a unique event in baseball history, a city's two franchises both took up residence in new stadiums in the same season. In the Bronx, the New York Yankees had a new home across the street from the still-standing old Yankee Stadium, and the Mets, in Queens, had also moved across the street.

On April 13 the Mets hosted the San Diego Padres for the official opening day of Citi Field. The next morning, after the successful debut of a new digital audiovisual system, employees of integration firm TSI-Global were working out some of the last remaining kinks in the stadium's signal distribution. Embedded audio from one of the broadcast truck docks was coming into the stadium embedded on the wrong channel. "I know we had that working last week," said Dave Potts, senior field engineer with TSI. At that point, just after the stadium's official opening, Potts said that his team was almost done implementing the AV system and was for the most part simply awaiting final punch-out from WJHW of Dallas, the designers of the system.

The design of the new Citi Field has some roots in St. Louis. TSI-Global, based in nearby St. Charles, Mo., had integrated the AV system at the then-new Busch Stadium, which opened in 2006 as home to the St. Louis Cardinals. Like that of Citi Field, Busch's AV system was designed by WJHW. Both Busch Stadium and Citi Field were designed by architects HOK Sport (now known as Populous) and built by general contractors Hunt Construction Group.

Citi Field's AV system also shares many elements of that of similarly sized Busch Stadium. Both systems are powered by Crown CTS series amplifiers—more than 210 units for Busch and 242 in Citi's case. BSS Soundweb London BLU systems process the signals for both systems via an Ethernet-based CobraNet architecture. But advances in technology since 2006 allowed WJHW and TSI to grant more power to the Citi Field's system operator. Specifically, Harman's System Architect software gives the operator unprecedented control over and monitoring of individual system components throughout the stadium's bowl, press boxes, luxury suites, restaurants, stores, and other areas.

The platform also represents an advance because it can stand alone. System Architect controls both the amplifiers and the DSP system (the 40-plus London BLU boxes around the stadium), which means that operators do not need to switch computers (typically done via KVM switching) to move from monitoring power amplifiers to adjusting DSP. Josh Beaudoin, who worked as a consultant at WJHW during the design phase of the process, designed the audio portion of Citi Field's system. "The ability to now both monitor the BSS and the Crown from a single interface provides much better system monitoring capabilities because we can monitor heat in all the amplifier rooms from the remote System Architect interface," he says. "We can remotely monitor any audio that's happening in the box, and then lastly we can schedule things in the stadium from System Architect." (Beaudoin is now director of marketing, installed sound with Harman/BSS.)

Audio in the Citi

Jun 22, 2009 4:24 PM, By Trevor Boyer

The New York Mets' new Citi Field showcases recent advances in loudspeaker design, DSP, and monitoring/control.

The BSS London system sped up the commissioning process, according to Potts. "We were able to group speakers in such a way that Mark [Schultz, special projects engineer with TSI,] can actually bring up just those speakers within the BSS processor," he says, "and for each individual array or combination of arrays, he was able to have EQ, delay, high-pass, in some cases low-pass, compressor/limiter level, meters, mutes, polarity—anything you needed. All though BSS."

Potts cites the audio from the video replay as an example of a difference between the function of the systems of Busch Stadium and Citi Field. "The difference in this system is that the audio operator controls absolutely every audio that's heard in the system here," he says. "At Busch, they have a sub-mixer from the video-replay system that's fed to the audio system." One measure of the degree of the AV systems' complication might be the miles of cable that snake around both stadiums. At Citi Field, Potts estimates that there's 200 miles of cable, much of which sits in neat, dense rows in two trays that hang from the ceiling of the service-level underbelly of the stadium.

For the New York Mets organization, the comparison is not Busch Stadium but Shea Stadium, which was quickly demolished as Citi was being built across the street (relatively quickly, by New York standards, that is). Shea had an analog audio system based on a center cluster of loudspeakers. At Citi, it's a digital distributed system, with a loudspeaker hanging every 30ft. to 40ft. around the top of its seating bowl. AX series (396, 364, and 344) and MK series loudspeakers from EAW cover the bulk of the seating at Citi. The long-throw EAW AX loudspeakers are custom units designed by the manufacturer and WJHW specifically for Citi Field.

In some areas, especially in seats under a roof, the low frequencies produced by standard long-throw AX loudspeakers would be excessive. "When you're under deck here, sound has a tendency to billow," Potts says. "It builds up, and that low frequency makes things unintelligible." According to Beaudoin, it's a simple result of the inverse square law that dictates how volume dissipates over distance. Ideally, you want a 3:1 to 4:1 ratio between the farthest reach of the loudspeaker throw and your closest listener. "Because of the architectural design of that stadium, the ratios were bad and we were forced to put the loudspeakers on club level," he says. "If the throw to your furthest seat is 100ft. and the measured SPL at that seat is 100dB, then somebody sitting right underneath that same loudspeaker is hearing about 120dB."

To alleviate that problem, EAW and WJHW designed "cancelling" woofers for the bottoms of the cabinets, which sit at a 90 degree angle to the cabinet front. Each cabinet has dual 10in. woofers, and technically they don't cancel frequencies so much as reduce them. "The concept is to create a companion source of same signal but different phase so as to provide cancellation of the main signal in areas where the main is excessive in level," says EAW co-founder and VP for strategic engineering Kenton Forsythe. "I say 'phase' as it is not merely inverted polarity. The adjustment is done with time and level so as to maximize the reduction where it is needed, with minimal reduction of the forward radiation." Beaudoin estimates that in Citi Field, the "cancelling" woofers effectively reduced the low frequencies by 6dB-8dB. Higher frequencies (above 500Hz) were not as much of a problem, because they respond much better to the directionality of the loudspeakers.

Audio in the Citi

Jun 22, 2009 4:24 PM, By Trevor Boyer

The New York Mets' new Citi Field showcases recent advances in loudspeaker design, DSP, and monitoring/control.

The seating is just one section of the stadium; for the purposes of the AV system, there's also the back of house (concession, clubs, bathrooms) and broadcast (camera positions, press interview facilities, etc.). More than 90 JBL Contractor Series Control 29s cover the stadium's private suites and certain fill areas near home plate and in the "homerun porch" in left field; and Tannoy CMS6 and Di6 DCT loudspeakers are installed in bathrooms and concession areas.

The bulk of the power for Citi Field's loudspeakers is supplied by Crown CTS-3000 amplifiers, which serve mainly the front-firing horns of the EAW AX series units. CTS-2000 amplifiers power the rear-firing components of those custom boxes. From the audio source—a Yamaha MC7L 48-channel digital mixer drives the system from the control room over home plate -- to the amplifier closets, audio travels as Cobranet over Cat-5; from the closets out to the loudspeakers, it's over copper wire.

At the same time as the company was designing Citi Field's audio system, WJHW was also at work developing the new Yankee Stadium's system. For both stadia, a new hybrid BSS signal-distribution scheme was used for the respective DSP systems that made them much more fault-tolerant than was previously possible. Beaudoin describes a "distributed" DSP design. "At both those stadiums we used smaller DSP processors that were linked together via both Cobranet and the BSS digital audio bus," he says.

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Cobranet runs on Cat-5 through network switches; it originates at the control room over home plate. That signal runs to each of three amplifier rooms above first base, third base, and centerfield. There's also an analog audio backup running to these rooms in case Cobranet fails. From these rooms digital audio bus links the BSS London BLU DSP boxes to each other in two directions via Cat-5. The boxes essentially form a ring. "That's how you get that redundancy," says Beaudoin. If one box fails, the DSP signal switches directions and there's no break in audio.

Beyond Audio

WJHW designed and TSI integrated more than just the audio system for the Mets' new stadium. For one thing, the company designed and assembled in its Missouri facility all the Middle Atlantic equipment racks for Citi Field's AV systems.

The stadium also has more than 800 video monitors throughout the facility in concourses, restaurants, club spaces, and an adjoining 200,000-square-ft. event space. Provided by Sharp, these Aquos LCD HDTVs display both the live game (via four inhouse channels) and dozens of local and satellite channels. Inhouse channels are produced in full 1080 HD.

TSI was not responsible for the hanging of the actual Sharp sets, but it was tasked with supplying a signal to each of the hundreds of monitor locations, as well as infrastructure to facilitate mounting, electricity, and a cable drop. Passing these HD signals around such a large building was a challenge, according to Potts at TSI, because all the channels had to travel down a single fiber out to relay locations. "We're not just distributing an RF signal," Potts says. "We're distributing the entire complement of DirecTV down that pipe also." From one rack room, the signals are distributed to a series of equipment closets, for signal relay out to the displays. Balancing the signals traveling on that single fiber was a challenge for the integration team.

Inhouse channels, such as the stadium's video replay, are generated as full 1080-line HD signals and encoded to MPEG using four Adtec Digital MediaHub-HD Pro encoders. The system then modulates the MPEG stream to an ASI stream. That stream enters a modulator, which converts it over to a QAM signal for over-the-air distribution.

TSI also integrated the cabling and connectivity for all the stadium's broadcast locations, such as camera positions, interview locations, and broadcast truck docks. (This broadcast "connectivity" required the building of several dedicated racks.)

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