The same technique can be applied to installed reinforcement systems as long as proper architectural positions are available. And, it takes confidence on the part of the system designer, confidence in choosing the correct positions and that loudspeakers won’t have to be moved.
In designing and building soffits (or closets as they’re sometimes called), it’s imperative that the cavities behind the loudspeakers are closed off, made to be acoustically benign. Further, loudspeakers must be anchored so they do not vibrate or move, and also, convenient access for service should be planned.
Finally, there can be no obstruction to direct energy emanating from the front of the loudspeakers. To this end, it is wise to remove the factory grill so that sound must only pass through the grill installed to conceal the soffit opening.
Backline Alignment
With systems for music or theatre application, another potential alignment problem can occur when sources on stage are loud enough to be heard by the audience at the same (or nearly the same) level of these sources are heard through the loudspeaker system.
Because the loudspeaker system is almost always positioned in front of sources, the combined sound of the direct source with the reinforced source will be smeared to varying degrees.
This is most commonly encountered with a pop or rock band using a trap drum set. Snare and kick drums are typically loud enough to project into the house at fairly high volume levels. If a show is mixed at conservative to “reasonably loud” sound pressure levels, most of the audience hears both the direct source and the reinforced source.
Due to the percussive nature of these instruments and the degree of misalignment that can occur (as much as 30 milliseconds), the “smearing” that results has a very destructive effect on the clarity or definition of the source signals.
Add the typically overly reverberant nature of most performance spaces, and you have an all-too-familiar situation where it’s next to impossible to produce a distinct rhythmic sound. More melodic or sustained instruments, as well as those lower in source level, are less affected.
But spoken word – in particular that of upstage actors projecting well – will display a decrease in intelligibility from this misalignment. Localization of sources to the stage can also be compromised.
Other musical sources that can be hindered include brass instruments, bass guitar, electric guitar and other percussion instruments.
Fortunately, it is relatively easy to minimize this problem by delaying the front-of-house loudspeaker system so that the arrival time of the direct sound is more closely in sync with the reinforced sound.
Synchronizing to the loudest acoustic source on the stage, such as the snare drum, provides much improved alignment for the majority of sound sources located elsewhere on the stage.
