Published in June 2006

Acoustic Compromises
By Russ Cooper

Not an option for multi-use halls.

     Until recently, Amarillo, a city of 230,000, was served by one multi-use performance hall: the Amarillo Civic Center Auditorium, in the city’s Convention Center. With all of its 2324 seats on one level, the proscenium-style auditorium was not a very inviting space, nor did it have good acoustics. To be economically viable, a new hall for the city would require 1200 to 1300 seats and also be multi-use.
     However, it was the architect’s vision to not design the typical multi-use hall with a stage house that works for theater, musical and opera, but that is a compromise for music, both acoustically and visually. Instead, Malcolm Holzman, of Holzman Moss Architecture, insisted on a “music room first” aesthetic, with the room adaptable for other uses: theatrically, acoustically and architecturally.

Home to Three Groups
     Opened in January, the Carol Bush Emeny Performance Hall in Amarillo’s Globe-News Performing Arts Center is home to three performing groups: The Amarillo Symphony, The Lone Star Ballet and The Amarillo Opera. Although the emphasis is on live, unamplified music, Emeny Hall must accommodate amplified music as well, from rock to pop to Broadway-style musicals. But this venue is not like other multi-use halls: It features one of the most unusual acoustical designs in the world today, developed by Jaffe Holden Acoustics (JHA) in conjunction with Holzman Moss, with theater design by Davis Crossfield Associates.

The Globe-News Performing Arts Center in Amarillo TX is home to the Carol Bush Emeny Performance Hall, which features one of the most unusual acoustical designs in the world today.

     Traditional designs of the best concert halls in the world are one room, rectangular geometries, “shoe-box” shapes such as Boston Symphony Hall and the Musikvereinsaal in Vienna. The volume of these rooms is such that a symphony orchestra at full sforzando energy levels does not sound loud or harsh.
     Acoustically, this means that the hall must have sufficient volume for the sound of an orchestra to develop properly, sustain and then decay naturally. The ideal volume to achieve the preferred great sound in these traditional concert halls is around 600,000 cubic feet. Symphony Hall and Musikvereinsaal seat 2650 and 2044, respectively. To maintain the necessary acoustic volume for a symphony orchestra to sound great in a hall with a seating count of 1300 would require an extremely tall space that would have appeared and felt cavernous.
     The design team’s solution was to use a room-within-a-room concept. The inner room would provide the architectural boundary of the space, thus offering the small-theater feel of an intimate and warm, inviting space. The outer room, which would be coupled acoustically to the inner room through strategically placed openings, would provide the extra volume necessary for the proper acoustics (see Figure 1).

Figure 1. Emeny Performance Hall Section Acoustical Systems.

Figure 2. The traditional shell design.

Traditional vs. ‘Shaper’
     Because JHA is experienced in perfecting orchestra sound on the stage side for a multi-use hall through its “concert hall shaper” design, it was determined that we would employ this design for the Globe Center project, but in a slightly different way. The shaper design uses a hard cap structure to seal off the upper stage loft area to keep sound from escaping into this large, absorptive space full of drapery and lights. This hard cap must then move out of the way when non-music performances are on stage using stage line sets.
     The traditional approach is to use a series of portable towers and “tip and fly” ceiling panels. Setting the stage for orchestra concerts with this type of shell can take up to an hour with a crew of three to four people. The three or four ceiling panels live permanently on heavy counter-weighted or electric winch line sets that cannot be used for any other purpose.
     The width of the stored ceiling panels “kills” the adjacent line sets as well, eliminating up to 12 line sets for theatrical use for non-orchestral programming. The wall towers, although “nestable” in their design, take up valuable offstage storage space. Figure 2 illustrates the traditional shell design.
     Traditional orchestra shell designs have acoustical drawbacks:
• If the shell ceiling design is “open” (the openings between the panels are large), sound is allowed to escape into the absorptive stage loft.
• If the shell ceiling design is “closed” (the openings between the panels are minimal), the sound on stage becomes too loud and harsh.
• The volume of the stage platform is small in comparison to the rest of the room, which creates two distinctly different acoustical environments.


Figure 3. (Left) The Pepsico Recital Hall, Texas Christian University. (Top) The Bass Hall Ft. Worth TX concert hall shaper.
   

Figure 4 illustrates the concert hall shaper deployed in Bass Hall.


Problem Solver
     The “concert hall shaper” solves all the acoustical as well as theatrical difficulties of the traditional design. Here’s how it works: The stage house structure, by nature, is inherently solid and hard and rigid, perfect for reflecting all frequencies of sound! Why not use this nature to our benefit and create an acoustical volume on stage that couples or matches that of the house to create more of a one-room hall?
     And, why not visually match the stage platform architecture to the house architecture so the experience is of being in one room, not the traditional two-room approach of an audience chamber and then a stage inside a proscenium?
     The “music room first” aesthetic led to these fresh perspectives, and away from the acoustical compromises inherent in traditional multi-use room design.
     The overall design of the Globe-News hall is an evolution of a smaller scale design we developed for the PepsiCo Recital Hall at Texas Christian University (Fort Worth TX), where the entire room was a fixed structure with inner and outer rooms. In this design, adjustable acoustics control reverberation and openings in the inner room to the outer room coupled the two spaces acoustically.
     Still, the Globe-News Center orchestra shell differs from concert hall shapers of some of our previous designs, such as Tokyo International Forum, Bass Hall (Ft. Worth TX) and Gaylord Hall (Oklahoma City OK) (see Figure 3).
     The hard cap to close off the absorptive stage house in these designs was an element that moved into position from an upstage location and had separate wall towers that stagehands moved into place from an offstage storage location. The shaper in both Bass Hall and Gaylord Hall required the stage to be struck, and the ceiling was lifted up from winch points on the downstage edge (see Figure 4).


Figure 5a

Figure 5a shows the concert hall shaper. Figure 5b indicates the orchestra shell in place, and Figure 5c shows the orchestra shell in storage.


Figure 5b

Figure 5c


Single Unit Construction
     The Globe-News shell is a single unit construction consisting of an industrial materials mover, rolling gantry crane from which the shell hard cap is suspended, and lower ceiling and walls as well. The hard cap ceiling is attached to the top side of the truss between the cranes and consists of a thick plywood layer. The lower, articulated shell consists of thick MDO plywood with a finish stain constructed in three segmented arches with openings in between each segment (see Figure 5). This is the same material used in the inner room of the audience chamber.

Figure 6. The room-within-a-room.


     The entire assembly lives in an upstage garage. Instead of taking a crew of three or four up to an hour, moving the shell into place becomes a motorized operation managed with a handheld remote as small as an iPod and takes just two to four minutes.
     The shell is also a room within a room (see Figure 6). The inner wood shell has openings at the gaps between the three arches to the outer room that is bordered by the hard cap shaper ceiling and the side walls of the side stage wings. The cap ceiling intersects the concrete fly galleries over the side wings, thus completing the acoustically reflective outer room.
     The inner room, both in the stage and in the house, reflects mid- and high-frequency sound. More of the low-frequency energy is allowed to pass through to the outer room where it is reflected back into the house later, without too much loss in energy, to create a low-frequency balance of sound often referred to as “warmth” (see Figure 7).
     The outer room in the house has adjustable acoustic systems to tune the sound of the various ensembles and to dampen the hall for amplified programming. The adjustable systems consist of mid- and high-frequency absorptive velour curtains and mid- to low-frequency absorptive fiberglass sliding panels, as illustrated in Figure 8 and Figure 9. When the panels are compacted, this system is fully reflective; when the panel is opened, the system is fully absorptive.

Tuning the Room
     The measured reverberation times with various adjustable acoustic systems are shown in Figure 10. For classical symphonic programming, reverberation time can be as high as 2.5 seconds unoccupied and 2.2 seconds with full audience. For amplified programming, with the adjustable acoustic systems in place, reverberation time is lowered to 1.4 seconds occupied. The shape of the reverberation time curves shows a flattening out in the low-frequency region when the adjustable acoustic systems are in place, allowing for better room control and a tight bass sound for amplified pop performances.
     The pre-opening acoustic check of the hall included a week-long effort by JHA staff to tune the room for various ensembles. This meant attending rehearsals of various groups such as the Amarillo Symphony, Civic Choral Society, local pop groups, opera singers, the Harrington String Quartet, etc.
     We listened from various seats in the hall and worked with the music directors to get a sense of how the music sounded in the hall. We then used the adjustable acoustic systems to either dampen the sound or liven it, depending on the need. We also determined the best onstage location for the performers. Opera singers in particular want to find the stage “sweet spot.”


Figure 7. Sound propagation in the hall.

First Event With People
     During the tuning, the Globe-News Center took the opportunity to invite more than 500 local university and high school students to attend a presentation I gave on the acoustics of the hall. (This actually was the first event with people in the hall. It was a great success and fun as well). The presentation’s tie-in with the Globe-News Gilliland Education Center, although not explicit, made perfect sense. The Education Center is a rehearsal hall, acoustically isolated from the rest of the facility, that can accommodate the Amarillo Orchestra and serve as a classroom for distance learning, as well.
     The tuning week culminated in a hard-hat full-house concert for the construction workers and their spouses, donors, founders and design team members. Jaffe Holden prepared this event, emceeing and orchestrating the on-stage appearances by those artists who had helped us tune the room during the week, this time demonstrating the flexibility of the hall with the different adjustable acoustic systems in place. When the shell was moved into place, and the audience was advised that it was the only one of its kind in the world and made entirely in the state of Texas, they erupted into sustained applause.
     The acoustic success of the Globe-News Center hall is borne out by reviews of the first Amarillo Symphony concert, in which music critic Chip Chandler stated, “The first true highlight of the concert came with Copland’s Fanfare, featuring only the orchestra’s brass and percussion sections. It’s the kind of piece you want to enjoy with your eyes closed, letting the sound wash over you and in the orchestra’s rendition, with the new acoustic clarity, that’s just what was required. It was gorgeous, simply gorgeous.”
     Creating a multi-use hall with a “music first” aesthetic is a viable option for new performing arts centers. The costs and space involved in the storage of the shell must be balanced against the savings in operating labor and scenic space-saving potential, as well as the benefits of a no-compromise music performance space.
     For the city of Amarillo, which raised the $36 million for the Globe-News Center primarily from private donations, the effort and expense seems to have been worth it.
For more information, go to www. jhacoustics.com, www.holzmanmoss. com,
www.daviscrossfield.com.



Figure 8 shows the outer room.


Figure 9. Above: Acoustic model illustrates the Symphonic Condition, with the orchestra shell, baffles closed and no curtains. Below: Amplified Condition, with the proscenium closed, baffles and curtains deployed.

 


 
Figure 10. Measured reverberation times.


Russ Cooper is president of Jaffe Holden Acoustics, Norwalk CT.


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