The best of both worlds
Jan 1, 1999 12:00 PM, Timothy Thornton
Tens of thousands of religious organizations in this country own and operate sound systems. Among other factors, the size of each church, synagogue or mosque and the specific style of worship determine the degree of dependence upon sound reinforcement. The Second Baptist Church, Houston, led by Pastor Dr. Ed Young, has its own challenges and complexities that exceed ordinary church sound reinforcement. In fact, the tasks of its audio department more closely resemble those of a multi-disciplinary A-V operation in a sizeable rental company rather than those of a church, especially considering that the church maintains a separate, on-site broadcast production studio to record and televise services and special events.
The primary factors shaping the actual installation are significant. The main worship center, which seats 6,500, has an interior volume roughly equivalent to a professional sports arena. Consequently, the church uses more than 120 loudspeakers in nine different models. The amps produce more than 80,000 W of power and require a 300 ampere service.
To make matters worse, the church's acoustical properties are unusually reverberant and especially challenging because of a large, conical stained-glass ceiling over the stage. The focal point of the cone hangs directly over the pulpit. Standing at the pulpit, a light handclap produces seven discrete yet completely audible echoes, even with no mics. Two 809x609 (24 m x 18 m) acoustically reflective stained glass windows add yet another level of problems.
In addition, the music ministry, a vital element of the church's service to the community, regularly stages major theatrical and musical productions. Equal to Broadway musicals in scope, content and demand on audio, video and lighting, these productions meant that the new sound system's infrastructure had to provide far more than speech intelligibility.
For aesthetic reasons, the church administration decided that the primary loudspeaker cluster would be housed in a decorative gondola suspended 55 feet (17 m) above the stage and 25 feet (7.6 m) below the ceiling and was originally designed to hold the earlier system's horns and bins. A 13 ton (900 kg), 65 foot (20 m) scaffolding tower was erected on the multi-level stage surface to provide access to the gondola. The structure's construction required 28 men working for 10 hours.
When it came time to install the new system, the disruption of even a single Sunday service was not permitted. All work had to be coordinated to keep the previous system functional until the new one could take over. Consequently, we had to squeeze approximately $1 million of equipment and labor into the available time slot-from the final Sunday evening service with the old system to the following Sunday morning using the new. I had recently been appointed chief engineer at the church when the new system received the green light. The installation contract went to Audio Communications, Houston, a prominent contractor who had installed the original system 12 years earlier.
The system design uses a predominantly single-source concept to provide the required imaging to the stage, but it is also buttressed by a plethora of support loudspeakers. As the primary operator, I had the best possible set of tools. Over the weeks following the initial installation, I tweaked and tuned the system's many zones, extracting every bit of gain-before-feedback without sacrificing tonal quality. The combination of the strong central loudspeaker cluster supported by the many delay loudspeakers allowed me to achieve perfect intelligibility along with a local presence in each seating area. The complex system avoids undue excitation of the extremely reverberant room without damaging the audible imaging to the stage.
System details The heart of the system is the Apogee 3x3 tri-amplified, horn-loaded concert loudspeaker. A cluster of five 3x3s installed in the gondola provided coverage from the middle of the seats on the main floor to the middle of the first balcony. Luckily, the 3x3s fit in the gondola with barely an inch to spare. A second cluster of seven Apogee AE-9s, also fully horn loaded, were mounted below the 3x3s. These were critically focused to provide coverage from the third row of the main floor rearward to the beginning of the 3x3s' coverage pattern. Precisely focusing these loudspeakers was a key element that allowed maximum gain before feedback in the front of the stage, which, in turn, enables the pastor to leave the pulpit and walk among the congregation.
Five wide-angle AE-2 loudspeakers were installed along the front of the stage, providing coverage in the first three seating rows. This zone of loudspeakers can be attenuated independently of the main system, eliminating problems that might occur when the pastor walks into their coverage area. The AE-2, a special-purpose, wide-angle (160 degrees) loudspeaker normally used for under-balcony fill, fit the coverage pattern needed in this zone.
The under-balcony area of the main floor is covered with 18 more AE-2s. Their usage here provides additional acoustical energy in the back of the room, evening out the differential in SPL from the front to the rear of the room. The AE-2s also serve to provide the less tangible effect of adding a local presence in the highly reverberant environment. Both the middle and upper balconies are likewise covered by 18 AE-2s, further serving to smooth the front/rear level variances, while maximizing intelligibility.
Although well situated in the pattern of the main 3x3 cluster firing from the gondola, the rear third of the main floor is augmented with four small arrays of AE-5 loudspeakers. Each array, mounted on one of four existing support pillars, provides the sound engineer with another tool to control levels and tonal quality in this zone independently of other areas. This section of the house is said to possess the best audio quality, but it would otherwise be one of the weaker spots because of its distance from the main cluster.
The extreme left and right fringe areas of seats are also covered by AE-5 units mounted into the wall surfaces that form the edge of the stairs leading to the choir loft, which houses 300 vocalists. These loudspeakers provide level and intelligibility in areas out of the main cluster's direct radiation pattern.
Finally, four AE-12s, a dual 18 inch (457 mm) subwoofer, round out the loudspeaker compliment. Two of each are placed on either side of the stage and bolted to the floor. They provide bass for track playback and reinforcement of the orchestra. The AE-12s are fed through a delay line to bring them into acoustic alignment with the primary central cluster, which is about 30 ms to 40 ms behind the subwoofers because of physical positioning.
By using a dominant central-source system with multiple delayed support zones, it was possible to achieve a uniform balance throughout the room. This would have been unobtainable with a single-source only approach. The system design retains strong stage imaging, however, which would have been impossible with a fully distributed system. The application of two design philosophies resulted in a system that exploits the best of both worlds.
Amplification All power amps used in the system are Apogee's DA-800s. The DA amps have an on-board microprocessor that provides front-panel indication of load impedance, AC line voltage, output voltage, output wattage and channel temperature. Attenuation is set by a shaft encoder in increments of 0.5 dB. Considering the system's complexity, the DA-800 was useful in setting up and establishing proper baseline performance parameters. In a church, you get a performance opportunity only one day a week. Any tool that minimizes the time it takes to tweak the system is extremely valuable.
Future plans include updating the amps to incorporate Apogee's AmpNET system. AmpNET provide a means of monitoring and controlling the amps from a remote PC. Any amp that might exhibit a problem will be identified by the computer. Adjustments to the 41 amps can be made without sending a technician, and comprehensive logs of amp conditions are recorded and can be printed at will.
Processing and alignment Each zone received its own delay time and parametric EQ. Five Klark Teknik DN-728 digital delays and 20 Apogee CRQ-12 parametric EQs were the main alignment tools. All time delay settings and EQ curves were derived by using Apogee's CORREQT measurement system (computer optimized room resonant equalization technique). CORREQT measured delay offsets to within fractions of a millisecond, and corrective EQ curves were precise. In essence, CORREQT lets the system reproduce a musical full-range response without unduly exciting the room resonance modes that would have made music muddy and speech unintelligible. The CORREQT process also allows recon-figuration of the system delay times and EQ curves to accommodate the large special events held in the church throughout the year. Often, these events require relocation of the front- and side-fill loudspeakers, and EQ and delay settings need to be altered appropriately.
Ken DeLoria, inventor of CORREQT, said, "Only undesirable room resonance is removed, not the broadband or arbitrary-band cuts that one is forced to settle for when using 1/3-octave analysis and graphic EQs."
During the refurbishment of the main system, much of the FOH equipment was upgraded or supplemented. This included a 40 input AMEK Total Recall console, a 32 input Mackie console used to sub mix choir mics, a 192-point hand-wired patchbay and a Marantz CD recorder along with multiple DAT and minidisc machines. The mics include Neumann KM-184s and KM-84s, Audio Technica 4033s, AKG 414s and 460s, Sennheiser 421s, 441s and MKE-40s, and a Schoeps podium mic.
An Apogee CRQ-12 was used for EQ and feedback suppression of the podium and the pastor's wireless lavalier mic. Two channels of Dolby CAT 430 frequency-selective noise gates were also added to eliminate the reverb tail generated from the PA getting back into the open mics. Although expensive and offering only subtle change, the improvement from the Dolby unit and the carefully adjusted parametric EQ provided an extra measure of control upon which we regularly relied. We worked under adverse acoustical conditions, and every decibel that we could squeak out of the system would make an important difference.
The importance of letting the pastor focus fully on his message to the congregation without distractions from the sound system cannot be overemphasized. Unlike entertainment requirements, a gathering for religious purposes cannot let sound take a back seat to lighting, video, staging or any other element. Otherwise, the purpose of the assembly could be lost with the possibility of more harm than good.
Installation notes The task of installation was formidable, and Audio Communications handled the job with the skill that comes from only a veteran organization. The system required more than 7 miles (11 km) of wire, much of which was plenum cable. Wire paths were difficult to find, requiring the installers to spend many hours in the attic in 125 degreesF (52 degreesC) heat without air conditioning.
Brackets for the pillar loudspeakers were custom fabricated by a local shop and welded to the pillar support columns. This became possible after extensive excavation into the plaster facade of the columns, which demanded extensive artistic refurbishment following the welding.
Foremost among the installation challenges was the task of placing the 2,320 pounds (1,044 kg) of loudspeakers into the gondola, 55 feet (17 m) above the stage. When completed, there was barely room enough for a man to enter the access door at the top of the structure. After the scaffolding was removed, access to the gondola was possible only by rappelling down from the ceiling. Fortunately, panels of the stained glass ceiling are removable, making for a straight shot.
Additional improvements Last year, the decision was made to decrease the size of the choir loft to accommodate two Barco video projectors illuminating two large screens. The original pews in the choir loft were removed and with them went the 280 loudspeakers that served as choir monitors. The pews were replaced with modern seating, allowing no room to reinstall the monitors. This problem was solved by three Apogee C-3 concert loudspeakers in the gondola that pointed rearward into the choir loft. The C-3 is identical to the larger 3x3 with only one sub and one low-frequency horn (where the 3x3 has two sub/low-frequency horn combinations), thereby reducing the height from 45 feet (14 m) to 30 feet (9 m). The addition of the C-3s delighted the choir members, who were never really satisfied by the monitor loudspeakers anyway. Its members say they experience the service, especially the pastor's message, as if they had seats in front with the rest of the congregation.
Reconstructing the 13 ton (11,700 kg) scaffolding to add the C-3s to the gondola was deemed too large to consider. The first effort took 20 men more than 12 hours to erect the structure and about the same to remove it. The cost was staggering, yet the work needed to be done. After considerable brainstorming, it was decided to rent a large platform like the type used by spot-operators in arena concerts. The platform was rigged to the structural steel above the stained glass ceiling and flown with chain motors. This way, the crew could ride the platform up and down to the gondola, greatly simplifying the installation.
While installing the three new C-3s, adjustments were also made to the main 3x3 system. Replacing the outer two 3x3s with C-3s allowed a sharper downward loudspeaker focus, which yielded better results in the seats in the coverage area. The larger 3x3s were limited by their size and could not be tilted far enough downward because of the physical constraints of the gondola structure.
Stage monitoring Second Baptist Church uses a sizeable orchestra as part of its worship service. Instruments typically include piano, percussion, strings, brass, guitar, keyboards, woodwinds and a large Allen pipe organ whose primary ranks are at the rear of the choir loft, making bleed into the choir mics inevitable. Many Sundays, a guest artist, usually a nationally known contemporary Christian performer, performs during the service. Most often, the artist will return in the evening for a full-blown concert following the evening service.
Monitoring is a critical function, especially when the pipe organ is playing mezzo forte or louder. Floor monitors added to the system include three Apogee AE-6 biamped multi-angle wedge types and 11 Apogee SSMs. The SSM is a small, high-fidelity enclosure that mounts conveniently on a mic stand. They are used on the platform for the church elders, which include the pastor, the music minister and the assistant pastors, all of whom are content with the loudspeaker's small size and natural, unstrained reproduction. Other stage monitors include EVI Audio and Community units used throughout the orchestra areas.
The stage monitors are mixed from the house, and the most critical inputs, such as the pastor's mic and podium mic, are split into two channels. This allows the console's channel EQ to be varied independently in the house and monitor sends. Additionally, the pastor's lavalier and the primary podium mic each use one-half of an Apogee CRQ-12 as an insert device. The CRQ-12 offers six bands of fully parametric band-pass filters, a 12 dB/octave LP and HP filter with adjustable turnover frequency, and low- and high-shelving filters with adjustable corner frequencies and boost and cut. I cannot overemphasize the importance of precision EQ to the success of this installation.
Summary Perhaps the best way to summarize the success of the thousands of hours devoted to the sound at Second Baptist would be a quote from the pastor, Dr. Young, who said, "The need for the proclaimed word to be reproduced with absolute clarity is essential. We have been thoroughly pleased with the pristine sound and positive service provided by our new system."
Acceptable Use Policy blog comments powered by Disqus
