The program I have been using recently is one called LARA/Integral Acoustics. It uses EASE data, so most commercially made boxes can be imported. It has a convenient library of preconstructed rooms that correspond to most of the typical venues we encounter.

They are easily modified to reflect the exact dimensions of a particular space. Defining acoustical treatments is not necessary because LARA treats all surfaces as a perfect absorber. In other words, we are only modeling direct field coverage and not trying to predict how the sound system and the room will interact, so the time required to build a room is reduced to a minimum for the well prepared FOH engineer many of the venues have floor plans available on the web.

LARA prediction of direct sound SPL for upper level of a stadium.

For those that don’t, getting room dimensions can become part of advancing the show. But even if none of the information is available in advance, this program is so quick that a room can be modeled on site while the truck is being unloaded.

Once the room is built, there are a couple of ways to drop the sound system into the model. There is a library function where you can store all of the cabinet models you are carrying. The speaker locations are chosen by using simple X-Y-Z coordinates. You can build a cluster one cabinet at a time or use predesigned blocks of speakers that you have defined as clusters.

If you build the array with individual boxes you can change the pitch, roll and azimuth of each box independently. If you build with clusters you must change parameters for the whole unit. Each box or cluster can also be adjusted for output volume and delay. A chart is generated showing the exact location, height, tilt, volume and delay parameters for each box or cluster. This makes it a snap to put everything where and how it was modeled.

The program generates a color SPL map of the room at chosen frequencies. Audience surfaces can be chosen so that the model only shows coverage where the people are. Or we can look at all surfaces so that sound can be steered away from nonaudience areas to minimize the system’s interaction with the room. Individual cabinets or clusters can be turned on or off to see what contribution to the overall coverage is being provided by them.

In addition to SPL maps, the program will provide complex summation maps. These show the constructive and destructive interference patterns that are produced by overlapping coverage patterns. This enables you to see comb filters and the lobing they produce.

Unfortunately for us Mac guys, most of these programs are only available for the Windows world. But most of us have been forced to have at least one foot in the PC camp by now anyway. These types of tools keep coming along to make our jobs more complicated in some ways but simpler in others. And if we can hang the PA right the first time, we can spend our day tuning, tweaking and sound checking. But the bottom line is better sounding shows with more even coverage through the whole venue. And that’s what it’s all about, isn’t it? Besides, all this computer modeling will keep us out of the back room on the bus!

Bruce Main has been a systems engineer and FOH mixer on and off for 27 years. He has also built, owned and operated recording studios and designed and installed sound systems. He can be reached at bmain@vectorcorp.com.