After stamping his architectural imprint on the likes of Bilbao, Seattle, Los Angeles, and Bard College, architect Frank Gehry has added the Jay Pritzker Pavilion in Chicago to his list of impressive cultural venues. Standing 120' high, the pavilion is topped with Gehry's signature sculpted metal, this time in the form of stainless steel panels or ribbons (these have been described as everything from a “billowing headdress” to “an exploding Coke can”) that frame a stage clad in Douglas fir. As expected with Gehry, the design is eye-popping and fun.

Yet “inside” this exuberant architecture is a very serious symphonic concert stage designed as the first permanent home for the Grant Park Orchestra and Chorus. With 4,000 fixed seats (from American Seating), and room for up to 7,000 on the adjoining 95,000 sq. ft. Great Lawn, the Pritzker Pavilion brings state-of-the-art theatre technology and acoustic excellence to an outdoor venue that is used for five months in the summer.

The story behind the design of the Pritzker Pavilion is a long one. “We were working on this project as early as 1998,” says Robert Shook, design principal of theatre consultants Schuler Shook (he works out of their Chicago office). “There was an early design by the architects at Skidmore Owens & Merrill, who had done a master plan for the park. At that point there was just an architectural swoop at ground level and an audience berm, with sculptures on either side of the proscenium.”

Things began to change once the Pritzker family became the principal funders of the venue. “Frank Gehry was asked to redesign the sculptures and eventually he came on board to design the entire theatre,” notes Shook. “It became a major project once Gehry got involved.” Schuler Shook, as well as the acousticians and audio system designers at Talaske of Oak Park, IL segued from the original project to the new one.

“What was exciting about working with Gehry is that he asked us what our requirements were for the footprint of the stage, the lighting, sightlines, and seats, based on the end user's needs,” Shook notes. “Gehry's office took in all the criteria.” Todd Hensley, a partner at Schuler Shook adds, “It was an unusual way to work, for the architect to ask for all that information in its raw form, and unusual for us to provide criteria without sitting over a set of drawings together.” Both offer kudos to Gehry for developing a successful design around the givens. “The finished space is true to the criteria we had developed,” says Shook.

The stage measures 85' across and 38' deep and can hold an orchestra of 100 players. There is also a choral terrace behind the orchestra for an additional 150 people. “The choral area can be used for extra audience seating,” notes Hensley. While effectively a summer venue, there are glass doors that can enclose the stage as a rehearsal or reception space in the winter. One of the challenges during the summer is the angle of the sun during daytime rehearsals but, luckily for the orchestra, Gehry's swooping metal elements solve the problem. “They serve as a sun shade and offer protection from the rain, like the brim of a baseball cap,” Hensley adds.

For Shook, one of the challenges concerned the sightlines. “Even though Gehry's office was keen to provide more of a real theatre than a bandshell in a park, we knew we had to keep the audience slope to a minimum, and keep a gentle rise that would maintain the aesthetic of a park,” he says. “As a result we raised the stage more than normal.” If a stage height is generally 3'6” to allow the audience to see the floor, the Pritzker stage has been raised to 5'. “But,” explains Shook, “the first four feet of the stage are at a height of 4' to create a sunken apron that helps the people in the front row not feel that the stage is too high. This also creates a natural place for stage monitors that don't block the performers.” The sunken apron solves a potentially challenging sightline issue.

Above the stage, which is a dead-ringer for an indoor concert stage, there are 200 lighting fixtures, 196 “Dry Line” lighting circuits to the dimmer room, 70 Crosby rigging rings (each good for one ton), audio input jacks, network connections, and air-conditioning for the performers who need to be kept cool. The rigging and stage equipment is by SECOA, with CM Lodestar chain hoists.

The lighting system is by ETC, with both a Unison architectural control system and an Insight 3 console for the stage lighting. Stage lighting includes incandescent 575W ETC Source Four ® PARs with cold metal mirror reflectors, and two Lycian 1275 followspots. Ethernet is used throughout, with a fiber optic cable carrying the Ethernet to a house mixing position for the console. Various pre-sets are in use, for example, a jazz setting which brings the lit area on the stage down to just 30' across.

“There is actually a double orchestra lighting system,” explains Hensley. In addition to the incandescent fixtures, there are also Source Four PARs with 150W ceramic metal halide lamps that are the base lighting for the orchestra, helping to keep the heat and power consumption down. They also make the stage very bright, with over 200 footcandles. “We could use all metal halide to light the orchestra to solve the heat problem,” says Shook. “But the five-minute re-strike time is a problem in case of a momentary power failure. Thus the redundant system.” The incandescents can also be used to warm up the color temperature on stage.

Both sets of lights are recessed in a random pattern in the wood ceiling over the stage, with the fixtures behind holes with glass covers. “These were designed by Gehry's office for acoustic reasons, and look like architectural downlights with a cone and lens but there are actually Source Four PARs on pipes above the glass,” says Hensley. The architectural lighting also includes 200 Altman Halogen Outdoor PAR fixtures with blue, amber, and white dichroic filters. These light the metal spans of an architectural trellis that crisscrosses over the seating area and provides support for loudspeakers, while also creating an exciting piece of architecture that puts the audience under what Hensley calls “a modern architectural bower. The Altman fixtures also light the ribbons as art on nights when there is no concert.” Shook adds, “Adding colored light to a Gehry building is like dreaming in color.”

Acoustician Richard Talaske, president and principal of Talaske, also started work on the Pritzker Pavilion back in 1998, and was part of the switch to the new Gehry design. The end result is that the metal structure enveloping the stage serves to reflect sound and provides an area where sound-reflecting surfaces can be tucked into the architecture in front on the stage and reflect sound back to the orchestra.

“We worked with artistic and general director Jim Palermo, and both the orchestra and the chorus to create a stage that is large enough and flexible enough for their ambitious program,” says Talaske. “What you have is the stage end of a world-class concert hall, yet there are subtle acoustic differences from an indoor venue.” The acoustic environment here was designed to allow the orchestra members to hear each other well and play precisely together. “The sound reflects across the stage,” Talaske explains. “There are side soffits and the overall ceiling shape and relation of the ceiling to the walls has few if any right angles.”

Talaske points out that you can really hear the music, loud and clear. “Chris Willis, the sound engineer at the pavilion really understands symphonic music and this helps the mix,” he says. But the real backbone of the sound is a double system that combines a distributed reinforcement system with an acoustic enhancement system (LARES) that helps create the sense of being in a concert hall while you are really outdoors. “You can also tune the acoustic environment and tailor the pavilion to the needs of the music, yet maintain the original character of the room,” Talaske emphasizes. “From the least to the most reverb, there is not a drastic difference.”

The original design included the economical solution of poles to support the loudspeakers. “Frank Gehry did not want to see poles and came up with the idea for the trellis, and we loved it,” says Talaske. “It supports the loudspeakers and helps define the space. It seems as if you go ‘inside’ the seating area.”

Jonathan Laney, senior audio consultant for Talaske, notes that the Grant Park orchestra has traditionally played under the stars so that a shed with a roof, as seen at other summer festivals, would not work here. “But we wanted to create a better orchestral experience in the outdoor setting,” he says.

Laney had used LARES (Lexicon Acoustic Reverberation Enhancement System) in some indoor venues and knew that this technology worked in the orchestral arena and could add reverberation and reflections to an outdoor venue as well. “We first did a demo during a rehearsal and were asked to come back and do it again for a performance,” he points out. “The city, orchestra, and donors were so impressed that we were given the go ahead to add the LARES acoustic enhancement system to the project.” Steve Barbar of LARES Associates in Cambridge, MA, worked with the acousticians to lay out and optimize the system, while the team of Continental Electrical Construction Company, dB Integrated Systems, and dB Sound installed the audio system.

LARES uses specialized hardware developed in conjunction with Lexicon, BSS, and Frazier loudspeakers. The system uses a time-varying algorithm to maintain stability by shifting the output in time enough to maintain the stability but not enough to introduce tonal coloration. The sound reinforcement system includes a DiGiCo D5 Live console, Electro Voice Xarray and Xi series loudspeakers, Crown CTS amps, microphones by Scheops, Neuman, and Shure, and routing and processing via Crown IQwic/USP3CN.

“The challenges of an outdoor facility for orchestral presentation in an urban setting include higher ambient noise as well as an audience area much larger than that of a concert hall,” explains Laney. “An orchestra cannot cover this area without reinforcement. So we designed two systems. One being the reinforcement system that provides loudness, clarity, and localization to the stage. The other being the LARES acoustic enhancement system providing the reverberation and reflection patterns that give the sense of envelopment, or immersion in the sound.”

The LARES loudspeakers point straight down, essentially creating a sense of overhead ceiling reflection, with additional loudspeakers around the perimeter to serve as wall reflections. The sound delivered by the speakers is delayed to coincide with the arrival of natural sound from the orchestra. This facilitates accurate localization and makes the viewer believe they are hearing the orchestra live from an impossible distance. “We were adamant about the loudspeaker placement,” insists Laney, who lists among his concerns the need to minimize sound spilling from the park and minimize the effect of weather conditions on the sound itself. “The distributed approach worked very well here,” he says. “This is a great example of form and function coming together to create a wonderful concert experience.”

One other aspect that makes this project so successful is the physical connection to the Harris Theatre (an indoor venue for music and dance) situated to the north of the pavilion. “It was fascinating for us,” says Shook. “We were involved with both projects and they were originally designed to be discrete facilities on separate sites. But once the Harris relocated to Millennium Park, it was redesigned to share backstage facilities and dressing rooms with the Pritzker, allowing cost sharing in the building process.” This works out well since the Pritzker is used in the summer and the Harris in the winter, with only a few weeks of overlap.

“In the eyes of most Chicago residents and tourists, the Pritzker Pavilion is an artistic and architectural icon they are attracted to,” says Shook. “Then they discover it's great for music as well — not just a beautiful piece of sculpture but also a fabulous sounding theatre. That was the design team's primary concern.”