P.A. Basics
What does P.A. stand for?
P.A. actually stands for "public address" which is what sound
reinforcement was called about a hundred years ago. The first use for
microphones, amplifiers and speakers was to amplify speeches given by
politicians. Making your band louder is a much more noble application
of the technology.
What's the difference between "P.A." and "Sound Reinforcement?"
In prehistoric times (the '50s) sound systems just amplified the singer
-- pure public address.To make the rest of the band louder, you just
added more instruments. For rock shows in stadiums and hockey rinks,
even the biggest guitar and bass amps need to be made louder so you can
hear them in the back row. Now, every instrument is run through a large
sound system and "reinforced" so that everyone can hear every mistake.
So I need more amps to amplify my amp?
Probably not yet, but unless you've got a helluva set of lungs, you'll
at least need to make your singing voice louder. Your bandmates may
disagree.
What do you need to provide sound reinforcement for a band? A basic sound-reinforcement system consists of a mixer, microphones, cables, an amplifier, and loudspeakers. Some people also call this a P.A. system. Here's a look at each part of the sound-reinforcement setup.
Microphones
A microphone -- or mic -- translates the sound around it into
electrical signals that can be amplified. There are lots of different
mics available for all kinds of applications.
The first difference in mics is impedence -- either high or low. High impedence mics can plug directly into any musical amplifier without a preamp. They usually have a 1/4" phone plug at the end of the cable. The big downside is that you can't use a cable longer than about 20 feet without losing high frequency response. Most pro mics are low impedence. You can use long cable runs without losing response and they're less likely to pick up intereference. Low impedence mics almost always use a three-pronted XLR plug to connect to a mixer.
Most mics are either omnidirectional (they pick up sound from every direction) or unidirectional (they pick up sound from mainly one direction). You'll be interested in unidirectional for live performance. They convert sound energy to electrical enery in different ways -- dynamic, condenser and ribbon are three of the more common. You'll want to look at the dynamic models to start.
Mic Buying Tips
Your first mics will probably be vocal mics and there are literally
hundreds to choose from. Good pro-level vocal mics can be had for under
$100, with decent starter mics at about half that. Always buy the best,
most durable dynamic cardioid or hypercardioid (directional or very
directional) mic you can afford, one designed to stand up to abuse. If
a mic doesn't sound good, then no amount of mixing, signal processing
or heaps of woofers, tweeters, or anything else will make up for it.
You might be tempted to spend your money on a couple of cheaper
microphones instead of one good one. Buy the good one, and save up for
another good one. Bad microphones aren't worth the trouble. Here's a
tip: If you have more than one vocalist, it's a good idea to buy the
same type of mic for each one. That way, if the mikes get switched
around, or one gets broken, you won't go crazy trying to fix the sound.
Mixer. As soon as you have two microphones you need a mixer. The mixer controls the volume and tone balance between all the mics (and other direct inputs like keyboards or acoustic/electric guitars). Mixers are usually defined by the number of channels -- each mic or input gets its own channel. The number of channels typically starts at four and goes up from there. Mixers also have lots of knobs, but they're the same for each channel, so once you learn how to use one channel you'll know how to use lots of channels. A mixer should have at least the following for each input channel:
- one input (either low impedance or high impedance)
- input level/gain control (to get the loudest sound without distortion)
- treble EQ (high frequency tone control)
- bass EQ (low frequency tone control)
- left/right panning control (for stereo mixers)
- channel fader (volume control)
The output section should have at least one master fader, and if possible two. That way, you can send one output to the power amp and main speakers and a second one out to another power amp and monitor speaker(s) for the band. Mixers can also have additional channel inputs, expanded EQ, built-in effects and other bells and whistles.
Many basic mixers also have a built-in power amplifier, or two in the case of stereo mixers. These "powered mixers" are a good choice for a first system since they eliminate the hassle and complexity of separate power amps.
Mixer Buying Tips
A basic mixer should have at least four input channels, and in most
cases two or three times that many channels is more typical. If you
only have two singers, four channels may seem like enough now, but
you'll surely want to expand your system as you get more experience.
You may be able to save some bucks by buying a powered mixer. That's one with a built-in power amp. It not only saves money, but it's more compact and easier to lug around than a separate mixer and power amp. Just make sure that you aren't sacrificing mixer features for that built-in power amp.
Most manufacturers offer a "system package" that includes a powered mixer and speakers. The big benefit here is that everything is matched, tested and ready to plug in and play. This is often the best choice for your first P.A. system. A small vocals-only system for an electric band will start at around $500.