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May 2012

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From simple to scientific, a look at covering the bases to ensure optimal performance

by Chuck W Walthall

As we say in the South, “There are many ways to skin an opossum.” Such is the loudspeaker design process: each designer has his own way. Some processes are very simple and some are extremely scientific. The following article outlines some of the most fundamental elements all loudspeaker design processes must take into consideration. We can forgo discussing the types of loudspeakers, (two-way, three-way, subwoofers, etc.), and focus on the fundamental purpose of loudspeaker systems, define basic design criteria, and outline design configurations.

WHAT ARE THE FUNDAMENTAL DESIGN CRITERIA OF ANY LOUDSPEAKER SYSTEM?

When you consider the most basic, fundamental purpose of a loudspeaker system, you will discover it is simply to increase the volume at the listener’s ear. However, there are numerous other purposes of loudspeaker systems that extend well beyond the fundamental. Loudspeaker systems provide the tools audio designers and engineers use to create artistic audio images, specific sound signatures, and audio perceptions.

The loudspeaker design process begins with remembering the basic fundamental purpose of the loudspeaker system and building on that base with the many other purposes. As the process matures, the system design takes shape.

GETTING STARTED

Loudspeaker systems must provide even sound coverage to designated seating areas. Depending on the shape of the venue, multiple loudspeaker systems are often required to ensure equal coverage from seat-to-seat. The size and location of the seating planes is the first criteria that will begin to determine the quantity of loudspeakers required. History proves it is hard to provide even coverage to all seats from a single reference point (center cluster). However, digitally controlled column loudspeakers and line arrays are challenging the old notions. Both newer technologies are proving useful when minimal point sources are called for.

The loudspeaker system must provide adequate volume to the coverage areas. The source material to be reinforced (speech, music, effects) plays a role in defining the sound pressure level (SPL) required for each seating area. Coupled with the coverage criteria, the target SPL determines the type, size and quantity of loudspeaker devices that will be required to generate not only the proper coverage, but also the required volume (SPL) conducive to the program material.

Providing even coverage to numerous seating areas and delivering the required sound pressure level typically requires several loudspeaker systems per area. Creating a specific audio image is subject to the location of the loudspeakers and their coverage characteristics. We know the brain localizes on what it hears first, not necessarily what it hears the loudest. As such, a listener is going to localize on the closest loudspeaker system. By way of digital signal processing and numerous processing tricks, creating audio images is much easier today than it was in days gone by. The art of creating an audio image is experienced not only in motion picture theaters (surround), but in famous entertainment complexes, as well as performing arts venues. The ability to direct one’s attention in a specific direction or create an impact with excessive level is yet another tool the loudspeaker system provides to deliver an audible experience.

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