"Live" Sound 101


Stage Sound Basics
by David Knight
So you're gigging now, everything is starting to fall into place. But there's trouble in paradise; your live sound doesn't sound so great! What do you do, what do you do?

Well, if you have six thousand dollars and a seasoned sound guy, this would be the end of the article, wouldn't it? Yeah, I don't have that stuff either, so I'm going to dive into the basics of running your own "live" sound system. This will not be about owning or buying the hottest or most expensive gear on the market, just the basics. Maybe you have no experience-this will get you started. Maybe you have a little bit of time at the mixer, this might be able to clear up a few things for you.

Let's assume you're tired of renting your sound from that guy with the big stale garage on the edge of town. The equipment is older than you and smells like your uncle's jogging shoes. Let's also assume that you have or are in the process of acquiring the components to build your own P.A. You won't need a ton of stuff, here's a list of the basics.

MIXER

Inputs? You need to know how many inputs are required. Are you going to mic just the vocals, or have an input for every guitar, keyboard, drum, horn and vocal? For the latter, you'll probably want to attempt this after you get a few dozen gigs under your belt. Let's go with vocals, kick and snare drum and maybe a keyboard. This will take, let's say, six to eight inputs. The all-in-one mixer head available today is quite good. Some have as much as 600 watts of power (300 per channel, see next paragraph) and built in DSP-Digital Sound Processors. Cool effects! If you get hold of one of the older ones, they work great too, however they may not have enough power nor any effects. If you choose a rack mount mixer you're going to need....

AMPLIFIERS

The amp should be matched to the power rating of your speakers; or vice-versa depending on which you own first. How much wattage? Stay away from: Peak Power, Bridged and 2-ohm values. The one you want is RMS or true RMS. This means Root, Mean, Squared. It is a mathematical value that includes the load, duty cycle, cycles of the moon, tides and what you're wearing. Just stick with RMS power and you'll do fine. These amp figures apply to powered heads as well.

SPEAKERS

If you're playing in small clubs, 200 to 300 watts each, 2-way (12" or 15" and a horn) or 3-way crossovers (with an additional mid frequency driver). Larger clubs or outdoors? Use 500 watts each and up. You should only need sub-woofers if you're going to mic the bass guitar and the kick drum. 15" for small clubs, 18" for large. Always know what the ohms rating is for each speaker cabinet.

The very first thing to understand is "signal flow". When someone sings into a mic, exactly what path does it take to get to the speakers? Knowing this will help you to (1) set the proper levels (2) troubleshoot and fix problems (3) buy the right components, and (4) have a great sounding band.


Here's a nice Multi-Purpose Sound System to check out.

SYSTEM DETAILS
Mission Control / Rack / Power / Speakers

PA speakers PA components