Recently, Whole Hearted Pro AV LLC partnered with Harvest Church in Glendale, AZ to design a speaker system for their new sanctuary building. The room was about 120’x120′ with a 25’-deep stage and stadium seating going nearly to the ceiling.
Our first design included a high quality line array system with a variety of fills, amounting to $215,000 before installation. When the church got back to us with their budget numbers, however, it was clear we would have to develop a Plan B.
The challenge: Designing an effective, powerful, budget-friendly system for a room that can seat 2100 people
We knew that the key to this system would be the subwoofers. The initial plans for the sanctuary called for steps along the entire front of the stage, so the subwoofer array needed to be hung. Our experience alerted us to two things:
1.) Cancellation patterns that change by frequency — called “lobing” — would become a very real problem if the subwoofers were physically separated.
2.) Hanging a non-cardioid subwoofer would interfere with the musicians on stage and the overall frequency response in the room due to reflections off of the back wall.
We had recently installed a Martin Audio system for another client, comprised of CDD12 speakers and SXC115 cardioid subs, and achieved great results. The CDD cabinets are designed to produce a much wider response pattern at the front (close to the speaker) with the pattern tightening as you get farther from the speaker — and their dual-concentric speaker design allows integrators to rotate the driver assembly for horizontal mounting with no detriment to the coverage pattern. Inspiration struck, and we began modeling a system for this much larger sanctuary using similar components.
The process: Inspiration, experimentation, and field testing
Our first draft specified three CDD15s across the front of the room and three CDD12s as a delay about 50’ ahead of the mains. With only three cabinets across a room that size, however, there were still huge uncovered gaps at the front of the room.
Further experimentation in our simulation software (we use Ease Focus 3 by AFMG) revealed that by adding two more CDD15s at the front, everything fell into place — creating very even coverage throughout the room at every frequency.
Similarly, we tested several subwoofer configurations in this simulation and arrived at an effective solution. We hung two SXC118 cardioid subwoofers side-by-side and two more directly behind them in an endfire array.
The in-person results were startling. Onstage, the low end was mild and unobtrusive — but a few paces into the room, the bass became loud and clear. More importantly, low end frequency response was very consistent throughout the entire width and depth of the room.
To power this system, we provided two Linea Research amplifiers with built-in DSP. The 44C20M amplifier delivers four channels at 20,000 watts for each of the subs, and the 88C06M amplifier outputs eight 600-watt channels for the main and fill speakers.
One of our goals for this system was to provide some semblance of “stereo,” even in such a wide room. To achieve this effect, we routed the ”left” channel to the center and outermost speakers and the ”right” channel to the speakers in between them. This configuration does not facilitate visual panning — but it does provide a sense of space in the mix and enhances instruments with stereo outputs.
With so many speakers across the front of the room, we programmed delays and level drops to create the impression that all sounds were emanating from the center of the room (as compared to sensing sound coming from “behind” you). The CDD15 under the sub was the cornerstone of the system, with no delay. We delayed the adjacent speakers by 20 milliseconds and set them 2 dB lower; we then delayed the outermost speakers by 40 milliseconds and at 4 dB lower. Next, we delayed the central CDD12 by 50 milliseconds and the left and right delay speakers by about 70 milliseconds.
The results: Amazing sound at an affordable price!
After completing installation and tuning, we were proud of our work. The entire sanctuary enjoyed remarkably consistent audio with no significant frequency flares or dips. Just as importantly, we nailed the aesthetics; the speakers were nearly invisible and blended into the ceiling infrastructure. There was no shortage of volume, either — the following Sunday got loud. Many people commented on how clean things sounded: “It’s loud, but not at all painful.”
Harvest Church was well-pleased with the end result, and they continue to enjoy a speaker system which favorably compares to systems costing six times as much at other facilities.
