A Grand Old Room: Boston's Symphony Hall
Nov 1, 2002 12:00 PM, By Gregory DeTogne
In terms of sound reinforcement, Boston Symphony Hall is a tough acoustical act to follow. Opened on October 15, 1900, the grand old room was designed by New York architects McKim, Mead, and White, with the help of Wallace Clement Sabine, an assistant professor of physics at Harvard. With a reverberation time of 1.9 seconds and inward-sloping stage walls that help focus sound on the main seating area, the hall architecturally tames excessive reflection and echo through the use of shallow-built side balconies, a coffered ceiling, and statue-filled niches along the sides and rear of the auditorium.
Despite its fame as a venue for acoustical performance, the hall calls for sound reinforcement for a surprising number of events. Beyond the need to occasionally amplify a narrator or singer during a performance by the Boston Symphony, guest artists such as James Taylor, Bonnie Raitt, k. d. lang, Paul Winter, and Mary Chapin Carpenter — all of whom have accompanied the Boston Pops in recent seasons — frequently require amplification, as well. Along with vocal soloists, performers backed by their own full-range bands frequently join the Pops onstage, as well. For example, Alison Krauss and Union Station played with the orchestra not long ago, bringing everything along from stand-up acoustic bass and dobro to banjo, guitar, and Krauss's voice. In cases like that, the P.A. must be able to present a full range of sounds that blend naturally with the Pops without degrading the acoustics of the room.
Earlier this year, the task of upgrading house audio capabilities within the space was given to Steve Colby of Evening Audio Consultants, which is based in New Hampshire. To complete the project, Colby, a senior sound engineer for the Boston Pops as well as a frequent engineer and consultant for the Boston Symphony, assembled a group of seasoned professionals with collective experience in the room dating as far back as the late '70s. Included among the team was Mark Brosnan of Klondike Sound, a Greenfield, Massachusetts, firm that specializes in live applications and was founded by John “Klon” Koehler in 1968.
As Klondike Sound's chief designer, Koehler is living proof that just like Carnegie Hall, how one attains audio success at Boston Symphony Hall may well be a matter of “practice, practice, practice.” Having provided sound-reinforcement systems for hundreds of concerts within the space for the past 24 years, Koehler says the preeminent lesson he's learned from his experiences is that all sound-reinforcement plans must respect the room's distinct acoustical signature.
“There's a long reverb time in the hall, which is fantastic for an unamplified orchestra,” Koehler says. “That same reverb time, however, can prove to be problematic when you add sound reinforcement, unless it operates within a very narrow window lying between audibility and excessively exciting the room, causing unwanted reflected sound. Our goal with this upgrade was to ensure that the reinforced sources complemented the hall's legendary sonic integrity rather than opposed it.”
Brosnan agrees that the hall is an easy space to overpower. “It's really difficult to provide any kind of amplification within this space,” he says. “You have to be very careful about putting just the right amount of sound in the proper bandwidths, all while giving due consideration to the architecture and acoustics. The audience has to be considered, as well. You have a good number of serious symphony aficionados out there on any given night, and they don't want the P.A. to get in the way of the music.”
Colby says it's essential that a sound system in the room be of exceptional fidelity, because the acoustic environment is pristine and unforgiving of distortion and other undesirable P.A. artifacts. “The system must also perform with the same quality as a fine musical instrument in order to blend convincingly with acoustic sound being produced onstage,” Colby says. “Over many years of auditioning systems in this space, it was agreed between representatives of the artistic, management, and engineering teams at the hall that L-Acoustics systems best satisfied this requirement.”
A DELICATE BALANCE
The new system features a central cluster of seven L-Acoustics V-DOSC enclosures suspended above the proscenium, with a pair of dV-DOSC small-format array elements hung below. Descending from its lofty perch in a sweeping arc, the cluster is augmented on the ground by several portable stage systems, including a front-fill array featuring four L-Acoustics MTD108a eight-inch coaxial cabinets mounted on Atlas Sound MS-25E stands and a deck-fill system of stage left/right ground stacks, each comprising a pair of L-Acoustics dV-DOSC cabinets that are mounted on a dV-SUB triple-15 subwoofer. Adding to system versatility, the dV-DOSC deck fills can be replaced as needed with a pair of L-Acoustics MTD115a 15-inch coaxial cabinets for special lower-volume applications.
“Our accomplishments with V-DOSC components in the room are centered around both sonic performance and highly defined pattern control,” Koehler says. “When viewed from the perspective of the audio upgrade's main cluster, the hall's seating plan resembles an inverted keystone. That is, it's wider at the bottom than at the top. The L-Acoustics line-source array offers a precise image that is horizontally symmetrical for our needs, providing a clear focal point as the sound-reinforcement source. That's ideal for this application, because though there is a lot of cubic volume in the room itself, the space actually occupied by the listeners is relatively small.”
During the design phase of the project, the room underwent analysis using L-Acoustics Array software. “With the program, we were given the ability to model the room in different dimensions while experimenting in a virtual world with various trim heights and cabinet configurations,” Brosnan says. “Based upon our discoveries, we obtained a model of our proposed rig's overall pattern and directivity within a range of certain acoustical predictions plus the tracking weight of the cabinets as they were distributed among the various hang points.”
At the outset of the project, the installation team envisioned the central cluster as one that would employ an eight-box V-DOSC arrangement. “We opted to go with the seven V-DOSC/two dV-DOSC scheme instead for two reasons,” Brosnan says. “First, it made the cluster lighter, and more importantly, it gave us finer control over where we wanted the coverage pattern to end in relation to the stage. This latter factor is crucial due to the tremendous variety of stage extension configurations in use at the room. In the course of a single day's events, stage thrust can range from a standard 4 to 6 feet up to 35 feet. Given this range of activity, we needed a rig that could be easily adjusted accordingly. With the higher number of cabinets and increased vertical coverage offered by the seven V-DOSC/two dV-DOSC cluster, now we can do just that.”
The 120-degree horizontal coverage of the dV-DOSC enclosures covers the seating areas closer to the stage. When combined with the performance of their longer-throwing, 90-degree V-DOSC brethren hanging farther up in the array, the dV-DOSC cabinets complete the even coverage picture nicely within this anything-but-symmetrical application.
“Even though this is technically a fixed system, I think it would be fair to say it has a touring-sound soul,” Brosnan says. “We built this P.A. with the distinct ability to come in and go out in minutes as dictated by whatever is happening onstage. For Boston Symphony performances, it can be removed if need be. Then, later in the evening, if the Pops are going to play and it needs to come back, it can be reflown in a snap while the room is theoretically changing over from a raked floor to a cabaret-style setup.”
GOT IT COVERED
To facilitate the venue's multipurpose schedule of events, which range from orchestral performances to squash tournaments, the entire array can be taken apart in segments and moved out of sight in a matter of minutes utilizing a custom dolly system designed and constructed by Polar Focus of Hadley, Massachusetts. “Mike Akrep at Polar Focus worked with us to develop a clever system of heavy-duty wagons, which allow the cluster to be broken down into only three segments,” Colby says. “The wagon containing the top portion of the cluster even allows for the bumper and additional rigging to remain hooked up for storage and transport. This saves a lot of time when flying the rig.”
The central cluster draws power from seven PowerLight PL6.0 amplifiers and a pair of PL4.0 models from QSC Audio, and an additional PowerLight PL4.0 triumvirate is kept at hand to feed the stage systems. Pro Co Sound NL4 speaker cable was enlisted for the stage systems, and NL4 and NL8 lengths were cut for the central cluster. With the cluster hung at the end of a 100-foot cable run, the amps call a third-floor equipment room high above the stage home, making them ideal candidates for automated control supplied by QSControl, QSC's Ethernet-based audio network.
Appreciated for its ability to control the coverage of the central cluster without making any actual physical changes to the loudspeaker array, QSControl also provides identical levels of complete system monitoring, command, and troubleshooting from multiple locations in the house using nothing more than a laptop PC and an Ethernet connection.
“QSControl was selected for its simplicity and wide-ranging capabilities,” Brosnan says. “It brings an easy-to-use operator interface to the room, and that's important, because there are a number of engineers who use the system frequently — many of whom are coming in from out of town and aren't familiar with what we've done here. Now, using the system is so simple and intuitive that they quickly have it walking through its paces without experiencing a hitch.”
With QSControl the down-fill enclosures hung beneath the central cluster can be instantly turned on or off as needed. The versatile network is also used with QSC's DSP-3 digital signal-processing modules to control other amplifiers remaining from the previous system, which serve ancillary areas.
“Now we're able to make adjustments within every zone throughout the building, whether it's served by a QSC amp or not,” Brosnan says. “This can all be done from a single location by a single operator.”
Beyond what's offered by the rig's two CM16a QSControl amplifier network monitors, added system management is supplied through laptop control of four XTA DP-226 processors (one for the central cluster, one for the stage system, and two for controlling other smaller zone systems) running Audiocore software. Still more processing control is available through the use of eight channels of patchable Ashly Audio Protea graphic EQ and the considerable EQ and delay power found in the Innova Son compact digital mixing console, which is the centerpiece of the front-of-house mix area.
Colby's design also called for a 40-channel BSS Audio active microphone splitter, along with a new patch bay, a tie-line network, and infrastructure dedicated to making the installation of rental gear more streamlined. “The wide variety of production requirements, particularly in terms of RF microphones and monitor speaker systems, calls for a lot of temporary installs,” Colby says of the regular activity revolving in and out of the hall. “In the past, we spent a lot of time and effort integrating this equipment throughout the building, often in rooms accessible only by staircase. With the completion of the sound system upgrade, we provided facilities that allow us to install all of our rental racks in a central location that is secure, climate controlled, and only a short push from the loading dock.”
The system debuted with the opening of the 2002 Boston Pops season on May 5. With approval to build the system granted in mid-March, the project was a classic fast-track installation for Evening Audio Consultants. A rapid process of specification, ordering, and design layout culminated in several weeks of 18-hour days for Colby and his wiring crew, Robert Winsor and Joel Porter-Davries. Going right down to the wire, the project was wrapped up just two days in advance of the hall's opening-day deadline.
Brosnan says that although the system is permanently installed, it went in as smoothly as a rental rig. “Actually, this system represents something entirely different from anything you'd normally find in the touring or fixed installation world,” he says. “That's exactly what makes it just right for this hall.”
Gregory DeTogne is a writer, a communications consultant, and the owner of an editorial public-relations firm in Libertyville, Illinois, specializing in pro-audio accounts.
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