Location Is Everything

Mar 13, 2008 3:06 PM, By Mike Sokol

           

FOR SUCCESSFUL LIVE SOUND, SPEAKER PLACEMENT IS CRITICAL.

Some gigs are a real breeze — there's no feedback, the instruments and vocals are balanced, and the sound levels are comfortable for listeners in both front and rear rows. But other times you run into an audio nightmare — your speakers are belching pure feedback, the folks up front are sustaining permanent ear damage while those in back hear only mud, the club manager is steamed, and you may not get an invitation to come back.

These two strikingly different scenarios can occur in the same venue with exactly the same audio gear. What's the difference? In the first instance, performers adhere to the basic principles of speaker placement; in the second, they don't. When you violate those elementary audio rules, no sound system will perform optimally.

Most small bars and “critter clubs” — as local bands call Moose, Elk, and Eagle lodges — were never designed for the acoustic onslaught of rock 'n' roll. Start with some bad paneling, a linoleum floor, and a tin ceiling, then add a local garage band blasting away in the corner, and you've got a recipe for aural mayhem. Club owners typically don't spend much time or money on acoustic enhancements. They might build an 18-inch-high stage in the corner of the room, with a few dedicated 20-amp AC circuits, but beyond that you're often on your own.

The better you understand how P.A. systems work, the better your sound will be. All the advanced signal processors, compressors, and limiters in the world won't help if placement errors leave your sound system with inherent flaws. Here are a few simple speaker and microphone placement rules that will help you transform a potential gig from hell into a great-sounding show.

Speakers Got Altitude

I can't count the number of times I've seen P.A. speakers placed right down on the dance floor, effectively putting the horns at waist level for the dancers. While bass frequencies behave a lot like water, flowing around most obstacles, midrange and high frequencies act more like light beams — objects in their path interrupt and absorb them. When you place speakers down low, the people sitting in the front rows not only get an earful of high frequencies but also absorb and disperse them. Meanwhile, listeners in back hear lows without the midrange presence and high-frequency sizzle that make vocals stand out.

Figure 1: Elevate speaker cabinets so that the high frequencies project over the heads of the audience members closest to the stage.

What to do? Elevate! Most of the time you just need a pair of speaker stands (see Fig. 1). Many P.A. cabinets have an integral stand socket that allows you to mount them, raising that all-important horn above the crowd. I like to get my speakers as high as reasonably possible, with the horns at least 7 to 8 feet above dance-floor level. This has two desirable effects: it leaves high-frequency sounds unmuzzled, and it beams less sound directly at fans up front. You get less volume in the front of the room, where you don't need it, and more in the back of the room, where it makes a critical difference.

However, keep in mind that only mid and high cabinets belong up in the air. For single cabinets containing, say, a 15-inch speaker and a 1-inch horn, your only alternative is to elevate the whole enclosure. But if you have separate subwoofers, they should remain on the floor. Subwoofers actually operate more efficiently (and get louder) at floor level. Whenever you put a bass speaker up in the air, you instantly lose half of its power, and most of the time you need all the bass you can get.

Caution: remember to use proper speaker stands and mounting hardware when you elevate speaker cabinets. Be smart — don't put heavy enclosures on folding chairs or light furniture. Make sure you have the speaker stand's legs splayed properly, and never exceed load limits. Use sandbags or old gym weights on the legs so that wind (at outdoor events) or jostling from crowds won't tip the stands over. Tape down cables and route foot traffic away from stands to avoid injuries. You can never play it too safe.

The Right Direction

Figure 2: This typical speaker arrangement shows high-frequency dispersion patterns and includes a small speaker that's been added to cover tables at one side of the stage.

Like microphones, speakers have a directional pattern and tend to beam mid- and high-frequency sounds in specific directions at varying angles. You can group speaker patterns into two general categories: long-throw and short-throw. Long-throw speakers, which have projection patterns as narrow as 20 degrees, are used exclusively for concert sound systems targeting crowds hundreds of feet away. By comparison, most club speakers are short-throw, with dispersion patterns of 60 by 40 degrees or wider. This means most of the midrange and high frequencies project out in a cone about 60 degrees wide by 40 degrees high. If the audience strays outside this range, they'll mostly hear booming bass sounds and miss the vocals.

As a general rule, if you can't see the throat of the horn, you can't hear it. Try to aim speakers toward the most important part of the room. If you need to cover a group of listeners seated directly beside the stage, you may have to aim an additional set of small speakers to the side so everyone can hear (see Fig. 2). These speakers don't require a lot of bass response, but they should have a wide dispersion pattern if possible. I keep a set of Bose 800 cabinets in my trailer for just such contingencies. They have a very wide dispersion pattern and are not as loud as a horn-loaded cabinet, making them perfect for covering tables directly to the side of a stage.