From the Source

Tom Young Reports On
His Work At The Chapel

Sometimes you walk into situations where there is a significant reduction in the problems normally associated with providing good sound reinforcement. Such was the case with a project that I recently completed for The Chapel in Akron Ohio.

The sanctuary is in a 20-year-old facility and has several architectural features that render it a sound reinforcement system “dream” environment. Even though it is essentially a square room, the corner-positioned platform results in the sound from the platform being projected out into the audience space, with no parallel wall-induced reflections.

Tom is principal of Electroacoustic Design Services, El Cerrito, CA

The single balcony, truncated platform, rear corners and numerous well-designed slat-absorbers positioned throughout the space all help to prevent or control any potential hard reflections. The slat absorbers take up quite a bit of wall real estate and are designed to be effective over a wide range of frequencies. Clearly there was a very sound system-savvy acoustician aboard when this space was designed. Adding to benefits from the above architectural design features, my initial site visit (which included the usual schedule of five Sunday services at The Chapel) and

lengthy interviews with Music Ministry staff revealed a focused group of people who clearly understood the concepts of teamwork, self-discipline and musicianship. Not only are there no players with stage volume level “issues”, but The Chapel had recently made the successful transition from acoustic drums to an E-drum setup.

Based on recent experiences with other house of worship and secular performance venue projects, I suggested that they consider IEM’s (in-ear monitors) tied into a personal mixing system. Going this route would provide more input mixing options to each of the key members of the Worship team and in the process would also considerably reduce the tasks for the FOH mixing team. This approach would also help to resolve the sad condition of the existing stage monitor system and would free up platform floor space.

The sanctuary at The Chapel in Akron Ohio, after renovation.

Slat absorbers along the rear wall in the sanctuary.

I took advantage of the calendar and arranged to meet a crew of key members from the Music Ministry at NSCA www.nsca.org Expo 2000, where I escorted them around to the various booths for suppliers of IEM and personal mixing systems. This helped to resolve any questions or doubts that they were having.

One more significant existing condition that I found was the remarkably poor condition of the front-of-house (FOH) loudspeaker system. As lucky as The Chapel had been in the sanctuary’s architectural design, they had been paying a high price for the loudspeaker system design that had been installed 15 years previously.

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Sixteen (!) pre-Constant Directivity small-format high-frequency horns were crossed over into eight custom-made dual 8-in mid boxes (direct radiating) and those crossed-over into two under-damped direct radiating dual 18-in subwoofers. These were configured physically into three clusters installed into the center third of the canopy above the platform. Supplemental coverage to underbalcony areas was provided by poor quality recessed ceiling loudspeakers. The resulting overall coverage was far from even and there was virtually no pattern control from the primary

clusters below 4kHz. In fact, so much energy was wrapped down and back onto the platform that there were eighteen permanently suspended choir microphones, determined to be necessary to achieve the small degree of gain-before-feedback that they had.

The FOH loudspeaker system was fed a mono mix and the resulting soundfield was a confused mess of unaligned sources incapable of providing clear and intelligible sound - despite the exemplary acoustic conditions. Over the years more than half of the drivers had failed and the resulting coverage was even more a checkerboard of sound quality, ranging from “so-so” to quite bad.

New platform with acoustic renovations.

Old platform with absorbers and openings in rear wall.

Given all of the above, my design approach was quite straightforward. I planned to take advantage of the friendly acoustics and layout of this space and design a high-quality loudspeaker system that would provide even and wide-frequency coverage to all seats and with minimal spill down onto the platform or onto the walls and ceiling.

The Chapel has a very ambitious Music Ministry and most of the five Sunday services employ a large rhythm section and also full-size string and horn sections, a praise team and the choir, varying in size from 60 to 100 vocalists. Clearly there would be much to be gained by having a stereo FOH loudspeaker system. Aside from the obvious spacial mixing potential, when mixing many input sources it is often advantageous to employ panning as well as gain and equalization in the struggle to separate the many signals and create a clearly defined musical mix.

Along with the desire for a stereo loudspeaker system as outlined above, the size and shaping of the canopy above the platform would have prevented me from implementing a two or three cluster loudspeaker system. After considerable thought and discussion with the design team at The Chapel, I chose to specify four clusters that would be configured in stereo and as "Right, Left, Right, Left".

We all agreed that the reversed image for the outer seating would be acceptable. Supplementing the four two-box clusters (needed for vertical coverage) are three subwoofers that I chose to put up in the canopy and to separate. I did this for consistent coverage and also to allow DSP processing should their coverage be uneven due unforeseen coupling behavior and possible the effect of room modes.

While viewing the new loudspeaker system’s overall coverage, I was careful to ensure that the FOH mix booth would receive very good sound quality, for obvious reasons. (see drawing below)

Through my ongoing research into the best available loudspeaker devices, I have found that the X-Array installation series from Electro-Voice www.electro-voice.com provides very good sound quality for the money and a useful array of devices to choose from. For the project at hand, the X-Array model Xi-1123, with 100-degrees by 60-degrees coverage pattern, would allow specification of a reasonable quantity of loudspeakers that would provide close to ideal coverage.

Xi-2181 subwoofers have demonstrated very good frequency and transient response in my evaluations and the Xi-1082 has remarkable SPL output and frequency response making it ideal for the underbalcony coverage. Merlin digital processing and EV’s P-series power amplifiers were chosen for their very high quality and to expedite the ordering process for the contractor.

One of four new clusters with (2) Xi-1123 and (1) Xi-2181 subwoofer.

Old cluster with (10) HF horns and (4) MF loudspeakers.

Other equipment that I specified: Shure www.shure.com PSM-600’s (8 systems), DBX 2231 equalizers and 1046 quad compressors, Earthworks Z30X microphones (piano), ADC patchbays, FMR Audio RNC compressors (for IEM’s), an Intelix Psychologist personal mixing system, eight DPA-4022 cardioid condenser microphones for choir pick up, Aphex 320A Compellors, Shure DSP (for stage monitor wedges and also the EV Polar-Choice podium mic) and a LynTec sequential AC power system.

Once the sound system design was completed, the specification package issued and a contract awarded, the walls surrounding the platform were rebuilt - per guidelines from Artec Consultants of New York City - to provide substantially increased acoustic support. The design package also included a completely new lighting system and new lighting positions.

In October, 2000, when the installation was completed, I made a site visit to inspect the sound system and to conduct system measurement and preliminary system optimization. Upon my arrival, the Music Minister commented on his observations that there was too much low-mid energy in the orchestra seats. I could readily hear and see this once Smaart www.siasoft.com analysis commenced, and thus I applied temporary equalization to reduce this frequency range.

One month later I returned along with Bob McCarthy (a sound system measurement specialist and mentor to many) to conduct two days of measurement and optimization utilizing a SIM-II measurement system. During this procedure we further analyzed the mid-frequency build-up and identified it as being a result of interaction within the overlap region between the upper and lower cluster components.

I had specifically opted in my design to overlap in this manner to keep energy off both the ceiling and the platform. But I also had specified that the cluster rigging hardware be designed and installed with some built-in adjustability and for just this type of problem.

Once the upper loudspeaker cabinets were physically readjusted (requiring only two hours), we confirmed that the overlap problem had been minimized but at the same time we observed several disturbing new reflections coming from the ceiling and into the mid-balcony seats. Bob suggested that we try using readily available fiberglass panels suspended in front of the offending upper loudspeakers. After numerous changes in the positions of the panels, we found locations that were effective in reducing the ceiling reflections to an acceptable level and without otherwise impacting the coverage.

We then aligned the underbalcony loudspeakers, the lobby loudspeakers (used when the room is opened for overflow crowds), aligned and tweaked the subwoofers and also optimized the choir monitors (three EV Xi-1122’s). ElectroVoice provided more-than-adequate technical support throughout this project, including getting us an additional Merlin processor (on short notice) for additional loudspeaker branch processing.

Reports from the Minister of Music and parishioners have been continually and enthusiastically very positive since the system debuted in late November. After so many years of impaired sound, they are now experiencing virtually unlimited gain-befor-feedback, improved platform sound, complete coverage to all seating and much less limited mixing potential for the volunteer sound staff.

Credits:
Sound system design by Tom Young (Electroacoustic Design Services, El Oxford, CT. dbspl@earthlink.net ). Acoustic design by Larry King and theatre lighting design by Chris Darland (Artec Consultants Inc, NYC. www.artec-usa.com ). System optimization by Bob McCarthy (Bob McCarthy Sound Services, St Louis, MO. bobmcc@primary.net ).

Photo credits: Tom Young and Jim Long (EV).