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How to Isolate Subwoofers in a Church

Inside look at subwoofer platform in auditorium with 12-foot ceiling.>

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The design of a new sound system for the sanctuary of The Pentecostals of the Fox Cities in Menasha, WI, was particularly challenging. This 500-seat auditorium has a 12-foot ceiling, dictating loudspeakers that are very compact in order to not detract from the room’s aesthetics.

To meet this requirement, we chose premium two-way loudspeakers, with six of these cabinets flown in their horizontal cabinet position (with mid/high-frequency horns rotated), carefully placed in a distributed, decentralized arrangement.

Largely due to compact design of these loudspeakers, frequency response doesn’t extend much below 90 Hz.

Therefore, we also needed subwoofers to reinforce frequencies beneath the 90 Hz point to meet a stated design goal of providing a system offering true full-range capabilities.

Finding a location for the subwoofers in this sanctuary proved to be a challenge. Placed on the platform, they would tend to distract the musicians and singers while flooding the area with feedback-inducing LF energy. And the ceiling was far too low to consider flying them.

Fortunately, the construction of a sound isolation drum booth on the platform necessitated extending the platform outward. We seized this opportunity, deciding to put the subs under the platform extension.Of course, this direction presented its own set of challenges. The platform height would be a tight 24 inches, leaving much less than that to realistically work with.

Evaluating possible solutions, we chose a pair of EAW SBX220 dual-12-inch-loaded subwoofers that are only 18 inches tall while capable of handling the 5,000 watts we wanted to deliver to them. (There are other viable options meeting this criteria, by the way.)

The next challenge: Isolating the low-frequency (LF) energy produced by the subs from the platform. Without proper isolation, the entire space under the platform could tend to act as a “resonation chamber” causing uneven frequency response and feedback.

Photos: How to Isolate Subwoofers in a Church

Working with a Mark McLernon, a skilled carpenter from the church, we constructed an isolation solution, a two-chamber box that effectively isolates the low frequency energy from the platform.