REACHING THE MASSES
Apr 1, 2000 12:00 PM, Keith Clark
Designing and providing inconspicuous, custom-designed sound reinforcementat the Vatican's St. Peter's Square.
Stato della Citta del Vaticano, as the Vatican City State is officiallyknown in Italy, is beloved by Roman Catholics throughout the world as morethan a special place; it is an enduring symbol of their faith. Situated onthe right bank of the Tiber River, within the city of Rome, the sovereign,independent Vatican City State hosts the official papal residency. The sitehas evolved over several centuries, and its 0.17 mile superscript 2 (0.44km superscript 2) area includes countless buildings and monuments ofsignificance, including the Vatican Basilica, one of the greatest churchesof Christendom and featuring the magnificent dome of Michelangelo.
St. Peter's Square is the main entryway to the basilica, dominated by acolonnade that is considered to be legendary architect Bernini's finestwork. The square, reported to be built over the tomb of the martyredApostle Peter, measures more than 750 feet (250 m) long and 400 feet (130m) wide, and thus,it actually forms a long rectangle, bowed outward in itsmiddle section, as it leads to the basilica.
Millions flock to the Vatican each year, in general for the entireexperience, and specifically to attend masses and celebrations held in St.Peter's Square, some led by Pope John Paul II when his busy scheduleallows. Obviously, then, the importance of quality sound reinforcement inthe square is paramount. Often, more than 150,000 attend a single mass, andnot being able to clearly hear the words of faith and inspiration would bea major disappointment.
For more than 35 years, the original equipment, carefully designed by Dr.Ing. Pier Vincenzo Giudici, technical manager of Radio Vaticana, had servedthis role admirably. It was, however, becoming sorely out of date, and wasfalling short of modern expectations for providing intelligible audio tothe entire space. Further, with the approach of Jubilee 2000, a three-yearcelebration of the new millennium, the need for a modern soundreinforcement system providing optimum performance had become more thanevident. It was a necessity. The number of people attending Jubilee 2000events is expected to exceed the entire population of Italy.
The process of developing a suitable system for St. Peter's Square tookwell over three years and involved a diverse group of specialists. Allsound reinforcement issues at the Vatican are the responsibility of RadioVaticana, a highly capable technical group, with their primary dutiesfocused on maintaining the highest quality for the myriad live broadcastsoriginating on site.
For several years, the efforts of Radio Vaticana have been supported byAudium S.R.L., a leading sound company and distributor based in Milano. Infact, Roberto Beppato, the owner of Audium, enjoys a relationship with theVatican dating back to his youth when he was selected as the representativeof his native community, Lombardy, for a national event held there duringthe Holy Year of 1950.
"From this point onward, it was one of my goals in life to be involved withthe Vatican, to support their efforts in any way possible," Beppato said."This evolved into working with the broadcast staff, and eventually, hasculminated in providing them with the best sound reinforcement systemavailable for an application of this type."
When discussions commenced regarding a new system for the square, Beppatocontacted Kenton Forsythe, Eastern Acoustic Works (EAW) co-founder andexecutive vice president of product development, to get his input onseveral issues. Forsythe, in turn, toured the site, noting several of thedifficult factors that would make the project a daunting challenge.
First, of course, the system needed to cover hundreds of thousands ofsquare feet of space with optimum vocal intelligibility. Virtually allsurfaces surrounding, and in some cases, in the midst of the all-outdoorarea are stone, marble, brick and just about every other type ofnon-friendly acoustical material on the planet. Also, the Vaticanarchitectural staff was understandably adamant that any new system conformto strict aesthetic guidelines. Specifically, loudspeakers needed to be fewin number and as small as possible. Other top-shelf requirements includedextreme ease of use for system operators and the provision of a number ofconfigurations that could be quickly and conveniently enacted to meetvarying needs.
Another key player in the development process at this early stage was CraigJanssen of Acoustic Dimensions, Dallas, who also studied the sitefirst-hand and offered a wealth of ideas regarding acoustics and thepredominant issue of loudspeaker pattern control. Concurrently, Forsytheenlisted the support of several top EAW engineering staff members,including Stephen Siegel, vice president of engineering, and David Gunness,director of research and development, and several meetings with Dr. Ing.Giudici and Dr. Ing. Massimo Stoppa, chief engineer at the Vatican, wereheld to work out different proposals.
At the time, Gunness was in the early stages of developing a new line ofhigh-output loudspeakers, called the KF900 series, that would later proveto play a pivotal role in fulfilling the unique needs of the project.
"The diverse factors influencing the design meant that we would have topush the envelope in a number of ways," Forsythe said. "At the time, wewere looking to attempt to provide the required coverage, and particularlypattern control, with existing KF series products, such as the KF850 andits higher Q derivatives. Although this would have been theoreticallypossible, quite frankly, no loudspeaker created to that point would meetthe standards we all expected to attain."
Another new development also played a crucial part, provided by CrownInternational in the form of its new P.I.P.-USP2 high-speed digital signalprocessing modules, which simply plug into the back of the system's CrownCom-Tech CT-1610 power amps. This equipment, residing in a secured room onthe second floor of the basilica, can be completely controlled, monitoredand re-configured via IQ for Windows version 4.0 software on a host PC inthe operator's position, adjacent to the equipment room. The project markedone of the first uses of the USP2 technology with Crown's Jim Stembleheavily involved, providing direct support as part of a highly successfulimplementation. These components, joined by others, were formed into whatultimately resulted in the largest installed sound reinforcement system inItaly and one of the largest in Europe - a system meeting and exceeding alist of highly demanding requirements. Technical management of the wholesystem, leading to its start-up and the first ceremonies, was handled byAudium's Massimo Oluzzi.
Major real estate
As alluded to earlier, the physical layout of the St. Peter's Square ismost easily described as a rectangle anchored at one of its long ends bythe basilica. In front of the basilica is the churchyard, including a largestone platform mountable by steps on three sides, which serves as the altarfor masses and certain other services and celebrations. Portions of thisregion are generally covered by a canopy when in use. Walls define theouter side bounds of churchyard, running fairly straight for about 250 feet(85 m), where the Bernini Colonnades begin. The colonnades now define theboundary, forming a huge ellipse. This region contains a wide range ofstatues and other tributes, interspersed throughout. The end of thecolonnade ellipse leads to Pope Pius XII square, also bounded by side wallsand in turn leading to the primary access point to the square.
"The dimensions of the space tend to be larger than life," Forsythe said."For example, while the altar area looks small in relative terms, itactually measures more than 5,000 ft superscript 2 (465 m superscript 2),and that's just the portion of it covered by the canopy."
The sound reinforcement system has two primary applications, met by twodifferent configurations, explain both Audium Project Manager GuidoDiamanti and Oluzzi. These applications, combined with architecturalfactors, directly dictated loudspeaker location and other design specifics.The positions designated B1, B2, D1, D2, E1 and E2 on Figure 1 denote thepositions of six main loudspeaker clusters, all used for the "Main"configuration, one of the two primary applications. These mirror-imagelocations were largely pre-determined by the calculation made by Giudici.They were the sites of the previous system's loudspeakers, andarchitectural compromises were not forthcoming.
Two more significant loudspeaker clusters were positioned at the colonnadeon the right side, to accommodate the other primary application, served bythe "Angelus" configuration. After mass on Sundays at noon, there is ablessing ceremony from the pope's office window. The two clusters hereserve as the primary source, anchoring the image to the balcony, supportedby one of the "Main" configuration clusters when necessary.
As slow, steady progress was being made on the concept of the design,Gunness and EAW engineering were nearing completion of the KF900 seriesloudspeakers. They were explicitly designed to supply full-bandwidthcoverage over vast distances with extreme pattern control. This is attainedthrough several patented loudspeaker technologies combined with unique,complex digital signal processing. The overriding goal is attainingbroadband, uniform sound pressure levels in both the vertical andhorizontal planes at very long distances and with tight control and focusof sound throughout the listening area.
Part of this is addressed with Phased PointSource Technology (PPST), aGunness development where all horns and drivers of each loudspeaker areplaced as close together as possible so that in multiple arrays, they actas either a line array in the vertical plane or as a point source in thehorizontal plane. Close spacing of the drivers also makes for relativelycompact enclosures.
The other part of the equation lies in advanced digital processing,allowing the coverage pattern to be fine tuned, with the vertical axisactually steered. Thus, control in the horizontal plane is largely achievedwith horn acoustics, while in the vertical plane it's done mostly withelectronics.
Gunness began performing extensive modeling of the site, using hisproprietary FChart modeling software that helps maximize PPST. It combinesmeasured loudspeaker response with calculated digital signal processingresponse, predicting the effect of processing on directionality. Further,the modeling software helped define cluster composition and firing angles.Although the KF900 series includes a long-throw low-frequency loudspeaker,called the KF930, none would be required for this project. Providing thebest possible vocal intelligibility was the paramount sonic goal, to bematched by extended high-frequency performance for enhanced musicality.
"One thing became readily apparent during the modeling process," Gunnesssaid. "We could definitely attain the necessary bandwidth required of theclusters, and they would easily cover the required throw differences.However, we couldn't quite attain the necessary width of coverage requiredfrom the small array structures dictated by architectural concerns. TheKF900 series supplies 60 degree horizontal coverage, and we needed to gowider. As a result, we redesigned all of the horns for the loudspeakersused on this project to supply 45 degree coverage patterns, and this mappedout perfectly according to the modeling."
Another difficulty appeared at this point. The complex DSP required forprecision coverage would be difficult to implement from a logisticsstandpoint, and it would also strain the project's budget. As a result, EAWbuilt complex filtering networks into each loudspeaker, and combined withthe DSP capabilities of the USP2 modules, the necessary tuning precisionresulted. In addition, the loudspeakers were outfitted with 70 Vtransformers to help ease concerns about moving power over cable runs thatsometimes exceed 1,000 feet (300 m).
"Both the 45 degree horizontal pattern and the internal filtering networkswere compromises necessary to fulfill several aspects of the design,"Forsythe said. "Dave's modeling provided a good method for determining thepassive filtering and what this would achieve from one driver to the nextwithin each loudspeaker. So, effectively, this work was pre-configured toattain performance parameters that normally would be done digitally, butbecause the installation is dedicated and won't change at all, we hadreasonable confidence that it would work.
"Another benefit to this approach is that we were able to greatly simplifycabling - no small concern in a facility of this type - and it lowered thetotal amplifier and DSP count. Design goals were achieved but at cost andcomplexity savings for the client."
Dr. Ing. Francesco Pisano and Mario Frabotta from Philips Projects Italymanaged the installation and the commissioning of the system with thedesign team concurring that they did an immaculate, thorough job. Prior toinstall, all loudspeakers, supplied weatherproofed, were painted a customivory color to fit in with the historic surroundings better, and they areflown above the listening area, attached with custom steel bracketsformulated by Philips.
In the "Main" configuration, the B1 and B2 positions offer identicalclusters consisting of two EAW KF925 mid-frequency loudspeakers, eachcontaining three 10 inch (250 mm) cone drivers on the custom 45 degree(horizontal) horns. Flown one over the other, they are topped by a singleEAW KF915 high-frequency module, which includes five 45 degree horns with 2inch (50 mm) compression drivers.
The design team was able to effect a slight change of these "B" locations,pushing them back from where originally specified by about 20 feet (7 m);in other words, further into the churchyard region. Carefully aimed withrespect to the side walls to prevent early reflections, these two clustersprovide coverage out to the "D" positions, and they can also work in tandemwith a portable system used at the altar.
The D1 and D2 clusters must provide the most output, covering virtually allof the Bernini Colonnade region. This is achieved with slightly largerclusters, each with four KF925s in two over two configuration, topped bydual KF915s. EAW also developed custom downfill loudspeakers for thesearrays. Flown from the bottom of the clusters, these compact boxes handlethe extreme nearfield. The "E" positions, only requiring a maximum throw ofabout 200 ft. (70 m), offer clusters made up of only one KF925 over oneKF915.
"Output isn't usually the concern with the KF900 series," Beppato said."It's a matter of consistent coverage throughout the entire region, andwith proper implementation of processing, this is attained."
Now, the "Angelus" configuration. Two clusters were posted roughly on axisof the pope's balcony along the right side of the colonnade. One cluster,primarily covering the churchyard, includes two KF925s and a single KF915.The other cluster, required to cover much of the rest of the square,includes four KF920s (60 degree horizontal pattern), two over two, abovetwo KF913 medium-throw/downfill high-frequency loudspeakers, each withthree 60 degree horns and 2 inch (51 mm) compression drivers. Whennecessary, the E2 cluster can also be activated in this configuration tocover Pope Pius XII Square.
Processing and more
The digital delay function of the Crown P.I.P.-USP2 processing modulesproved a valuable contributor to the project, with Audium programming themnot only for time alignment between clusters, but also for precisionalignment of each loudspeaker.
"This allowed us to enhance the feeling that sound is coming from the realsource, particularly with the Angelus configuration, despite the immensedistances" said Oluzzi.
The USP2 modules also provide system wide processing, including parametricequalization. In total, each module offers full 24 bit processing for eachchannel of the system with each channel including eight independent, fullyadjustable filters, furthering the passive filters built into theloudspeakers.
The modules also monitor the state of the Com-Tech 1610 amps, offeringmonitoring of input and output power, dynamics, real-time load impedanceand temperature. IQ for Windows version 4.0 software, loaded on the host PCat the control position, serves as the hub for this aspect of the system.Routed to a Crown INT II interface in one of the racks, the softwarecommunicates with the modules, and the two elements work together to allowsystem designers to create enhanced graphical user interfaces. The resultis convenient and intuitive editing of all processor parameters. Presetscan also be configured and brought on-line with the click of the mouse,with all processing, level and monitoring functions reconfigured instantly.
"We took special care in creating the control windows for the differentsystem operating modes or configurations," Oluzzi said. "The goal was foroperation to be as simple as it could possibly be. The operators were ableto become quite fluent with this control format in a very short amount oftime, so there were no major learning curve problems.
"It's also impressive that the USP2 modules, despite their complete newnessat the time, have worked exactly as they're supposed to. They're stable,and that means the system, in general, is stable."
Because of the potential of strong reflections, particularly in thecolonnade zones, several Sabine FBX 2020 feedback exterminators have beeninstalled. These intuitive units automatically adjust their 1/10-octavenotch filters at critical frequencies, capturing problems before they enterthe system.
Interestingly, the system control position is ensconced within thebasilica, meaning that the operators cannot hear it during an event. Anetwork of cameras positioned in the square feed video monitors in thecontrol room, allowing operators to see what is happening. This is combinedwith the total audio monitoring capability supplied by the P.I.P.-USP2modules and IQ software viewable on the PC. Given that the system has allbeen pre-configured with optimum parameters, this location of the controlposition does not present much difficulty.
As mentioned earlier, a portable system usually supplies reinforcement tothe altar region. The definition of "portable," however, might bemisleading in terms of this system's scope. EAW provided another customdesign, this time for a compact two-way loudspeaker based upon its UB82stock product. Eight of these custom loudspeakers, called the PSP82 (PSP,in this case, designates Piazza San Pietro) for this project, arestand-mounted vertically throughout the listening area. The rear of thisarea, behind the temporary seating usually placed on the altar, includesfour EAW JF260 compact full-range loudspeakers also mounted on stands andsupplying coverage further into the churchyard.
All of these loudspeakers are plugged into custom panels distributedthroughout the area, receiving power as well as processing parameters. Thissystem can be used by itself for ceremonies contained just in thechurchyard, or it can be used in combination with the clusters in the"Main" configuration with appropriate delay parameters supplied by theP.I.P-USP2 cards to integrate the two diverse elements seamlessly. Stagemonitoring at the front of the altar is supplied by two EAW SM260 wedgesthat can be positioned as needed.
The entire system was fully implemented, tested and tuned well prior to thekickoff of Jubilee 2000. The entire design team participated in thisprocess, using SIA SMAART Pro version 3 software loaded on a laptop PC.Stemble supplied an RF Ethernet link that provided an interface with theCrown IQ network, allowing tuning to be done from the square.
"We based the tuning operation in a little white Fiat Van that allowed usto quickly move about the square to work on different portions of thesystem," Gunness said. "The RF link provided by Jim was invaluable, and theIQ System in general was extremely easy to operate and allowed us toquickly achieve the desired results. Combined with the capabilities ofSmaart, the tuning situation worked out very well."
Beppato noted that the years of planning, negotiation and developmenthelped insure a resulting system pleasing to all parties involved, whoreceived the blessing of Pope John Paul II together with Roberto Calvigioniand his crew of the Vatican ceremony department.