Sound Systems

Sound Systems

I Knew Jesus (Before He Used A Shure P.A.)

The rumors that Jesus used a Shure p.a. system for the sermon on the mount are probably not true, but the point is well taken. Whenever there are more than ten people in any one place and they're all trying to hear what one person is saying, the problem of sound-noise over people-noise arises. The fumbling, coughing, scratching, shuffling, jointsucking noises that come bouncing back off the walls at a rock concert are the competition that every group must deal with in trying to get their music across. The aesthetic evaluation of what they're playing and how they're playing it can become secondary to their proficiency on a technical level.

Sound is produced by the vibration of solid matter. That vibration sets the air around the matter vibrating. And that vibration eminates in all directions from the source of the sound; it keeps going until it is absorbed or dissipated unless it strikes some hard, smooth surface in which case it's reflected back in the general direction from which it came. These are the variables you have to deal with in trying to make effective sound. In a practical situation it goes like this: a speaker vibrates to produce a sound wave, the sound wave eminates from the speaker, the physical presence of the audience absorbs much of the sound, some of it bounces offithe walls of the concert hall to create secondary, delayed repetitions of the sound known as reverberation, and, depending on the amplitude of the sound, the folks in the back row may or may not hear what's going on.

You may never have worried about any of this when you set-up your p.a. system. The attitude that with,, enough speakers and a powerful enough amplifier you've got a great system is alright, but to have really effective sound you've got to get into it a little deeper than that.

Before you buy a sound system, consider what it's going to have to do for you. Are you going to run one voice through it, three voic,es, voices plus some of the instruments? What's the .competition going to be. .. three Dual Showmen, a stack of Marshalls, ten Orange cabinets? How big are the halls you dream of playing in? All these parameters must be set prior to investing in a sound rig. If they're not you're either going to get a hernia from lugging around too much stuff or your audience is going to think you're the Ventures.

The components of a sound system are: microphones, an audio mixer, a power amplifier, and speakers. They're all hooked up in a series in that order so when you sing into the mike the sound comes out the speakers. Each element of the system is.critical to the performance of the other components and the overall effectiveness depends on the inherent capabilities of the system plus where it's being used — and how you're using it.

Working our way along from the source of the sound, the first consideration is the microphone. This is the unit responsible for changing the sound waves that you or an instrument are producing into a corresponding series of electronic signals which will be mixed with other sound signals, amplified, and then rfeproduced.

Any number of manufacturers are producing mikes which are excellent for sound system use. The major brancls include Shure, ElectroVoice, Sony, and Turner. Mikes come in a variety of types arid formats: uni-directional, omni-directional, dynamic, electret-condenser, condenser, cardiod, super-cardiod, ribbon. . . the differentiations go on and on. You're going to need uni-directional dynamic or uni-directional electret-condenser mikes. The dynamic is more rugged than the electretcondenser which has a battery power supply built into it that has to be changed occasionally, but the electret-condenser is more sensitive to the coloring of the sounds coming into it. Both of these types must have a unidirectional pick-up pattern (either cardiod or super-Cardiod) or else you're going to get feedback and muddy sound.

Mikes of these types are either lowimpedance or high-impedance (sometimes low-Z or hi-Z) and this impedance rating determines how long a cable you can run between the mike and the mixer/ amplifier. With a hi-Z mike you can run about twenty feet of cable at most, with a low-Z mike you can run a hundred feet or so. (A low-Z mike is any mike with an impedance rating of 600 Ohms or under). Get low-Z mikes. Most mikes are available eight hi or low-Z, but often the inputs on mixers or amplifiers are only high impedance. In this case you'll need a "line matching transformer" which must be attached to the end of the mike cable and then plugged into the mixer or amp to switch the signal from low to hi-Z.

Budget from $50 to $100 for each mike. Any less and you'll get crap, any more and you'll be buying mikes that are too sensitive for the rough handling and shouting that they're going to be subjected to. Sure makes a whole series of mikes especially for vocal applications as does Electro-Voice.

Using more than one mike requires an audio mixer. This ,is a unit which accepts the signals coming from the different mikes and allows you to set the levels of these^signals in relation to each other — louder, softer, or the same - before they're amplified. Mixers start at about $10 and run into the thousands, their cost depending on the number of mike inputs, the facilities available for monitoring' the signals, and the extra controls included over and above a volume control for each input and a master volume control for the output signal. Sony's MX-12 is a great $100 mixer which they've stopped making, but you can still find in some stores. Shure has a whole series of mixers from just under $100 to about $250. But none of these mixers compare to those built-in to the mixeramplifier combinations that are being designed by Shure, Ovation, Kustom, Sunn, Altec, Lansing, Cerwin-Vega and others for rock use. These combination units allow you to adjust the frequency response of the sound signals - add bass and treble — as they run through the mixer and amp.

The amplifier is important to the total sound system for two reasons: it strengthens the signal and it maintains its validity. You must get an amp that has enough power to drive the speakers that won't distort the sound signal as it amplifies it and which you can adjust to meet the demands of the hall. Amps are rated in terms of their wattage. Often this will be RMS wattage, at other times the wattage ratings will be in "music power" or some other term. This is confusing and is determined only by the whim of the manufacturer.Try to get an RMS evaluation of the amp you're planning to buy. This signifies the greatest amount of power that you can depend on. 100 watts RMS is a lot of power. It can also be expressed as 300 watts peak music power, which sounds like more, but is the same rating. The extra 200 watts signifies that the amp is capable of momentarily providing more power, but can't be run continuously at that level.

Finally, we get to the speakers. There are two general types of speaker systems on the market: box and column. A box speaker is just that - a speaker in a box, sort of a bigger version of your hi-fi speakers. A column is an elongated speaker box with a number of speakers in a row along its length. Column speakers are popular and they give out good sound if they're positioned properly. Box speakers, such as those made by Altec Lansing under the brand name "Voice Of The Theater" are even better, but again, they're only effective if they're positioned correctly in relation to the audience-area you want to reach.

A number of guitar and amp companies have developed sound systems that come complete with mixer-amp, speakers, and all the trimmings - sometimes including mikes. These make it a lot less confusing to buy a sound sytem, but you have to be careful not to get a cheap "ready to go" system. It's going to cost you over $1,000 to get a sound system for small and medium sized applications, more if you're planning to open your own Fillmore.

Among the medium priced systems I'd recommend are the Ovation IC100, the Shure VA300, VA302, or equivalent, the EMC systems, an Altec Control Console plus Altec speakers, Kustom's model 302, 303, 602, or 605, the Acoustic model 854, and any of the Sunn systems.

The rock trend at the moment is to use smaller guitar amps and to then run all the sound through the sound system rather than depending on the guitar amps^to fill the hall. This is fine and creates no problems so long as you keep two things in mind - you're going to need as many mikes and corresponding input channels on your mixer as you have amps, voices, drums, and the rest, you're going to need enough speakers so that all this sound can be dispersed properly without distortion. I'd suggest you double the size of your sound system if you're planning to mike other things besides voices — twice as many mikes, mixer channels, power wattage of amp, and speakers.

An extra sophistication to any system is a monitoring set-up so you can get some idea of what the sound is like and what everybody else in the band is doing. There is usually a "monitor" output on most good mixers or mixer-amp units — the signal is taken out of that output and run into the monitor amp where it is amplified and then sent to the monitor speakers. Peavey, Bose, Altec, and others make special monitor equipment, but you can also use any small speaker and small amp to set-up a monitor system.

Try to think of your sound system as the most important amp you have onstage. xSpend as much time choosing it and learning how to use it as you do with guitar and bass amplifiers. It is* after all, the key to a good performance being heard past the first row. And that's what you're up there for, isn't it?