PA System Setups Brought to you by PA Systems come in many different shapes and sizes, ranging from the very elaborate systems used in large stadiums all the way down to a simple microphone patched into your home stereo. Listed below are several of the most common setups. Example 1: The Bare Bones

The above example is about as basic a system as you can get. Hooking it together is relatively simple. The most important thing to remember when hooking up any size PA is the direction of the signal. This is indicated above by the red arrows. The signal starts with your mouth (or drum, or horn, or whatever), then goes through the microphone into the system, then routes its way through the amp, and finally into the speaker where it leaves the system as a much louder sound. A good rule of thumb is to remember that when plugging something in (like an amp), whatever you plug into the input should be coming from the direction of your mouth while whatever you plug into the output should be heading toward the speaker. An easier way to think of it might be to think of it as a river, the microphone being upstream, the speaker being downstream, and the amp being a reservoir in between. As the water (the signal) flows from upstream (the Microphone), it must enter the reservoir (the amp) through an input, and then exit the reservoir through an output until finally, it reaches the downstream side (the speaker). So, that's the theory (complete with a picturesque metaphor). Now here is the reality. In the example above, you would plug things up in this order.

1) Plug the mic cord into microphone (There is only one place to plug it in. Technically it's an "output").
2) Plug the other end of the mic cord into the "input" of the amplifier (remember, input is coming from the microphone).
3) Plug the speaker cord into the speaker "output" of the amplifier (the signal is flowing out of the amp toward the speaker).
4) Plug the other end of the speaker cord into the "input" on the speaker (the signal is coming from the microphone through the amp to the speaker.

And there you have it. Of course, although it will amplify the sound, this particular system won't be of much practical use to you in any real life playing situation. It still lacks three essential ingredients.

Example 2: The Essentials



With the addition of a mixer (soundboard), an equalizer (EQ), and a set of full range speaker cabinets, we have a small PA system that can be used both for rehearsal and for some gigs. The principle of signal direction stays consistent. As the arrows indicate, the signal again starts at the microphone passing through each component in turn until it reaches the speakers where it exits the system as an audible, much louder sound. It is important to note the order in which the components are hooked up. No matter how many more components (such as effects or compressors) are added, these basic building blocks should always line up in this order relative to each other. The EQ should always be connected somewhere between the output of the mixer and the input of the power amp. The microphone should always be on the input side of the mixer, and the speakers should always follow the amplifier.

Warning:
Never plug anything other than a speaker into the output of a power amp. A "speaker out" connection carries a very strong signal that can and probably will cause damage to the other components.

Example 2a: The Powered Mixer



The powered mixer (pictured in the center of Example 2a) is very handy in that it combines the amplifier, the equalizer, the mixing board, and some limited effects into one relatively compact unit. These can be very convenient in some situations. They are especially useful for smaller acts and great for rehearsal. In general, they are smaller and easier to transport, and easier and faster to hook up. Also, in many cases, buying one combined unit like a powered mixer can be considerably less expensive than buying the pieces separately.

Example 3: Small Practical PA



In example 3, we have added monitors and effects. The monitors are the speakers that face back toward the stage so that the people there can hear themselves singing. They require a separate equalizer and amplifier and are hooked up in the same configuration as the mains (mic to mixer to EQ to amp to speaker), except that the cord running to the input on the monitor EQ is coming from the "Monitor out" channel on the soundboard rather than the "Main out". Basically what has happened is that the signal that has left the microphone has been split by the internal electronics of the soundboard into two separate signals. One signal is then routed through the "monitor out" into the monitors while the other is routed through the "main out" into the mains. This makes it possible to adjust the sound coming out of the monitor speakers separately from the sound coming out of the main speakers.

The effects help to thicken out or modify the sound that is going through the PA system. There are many different kinds of effects including such things as delay (echo), reverb, and chorus. These can be hooked up "in line" or directly in the path of the signal, but are much more versatile when hooked up in an "effects loop". An effects loop is created when a signal is sent out of the soundboard into and through whatever effects you are using and then "loops" back into the soundboard. Once this loop is set up properly, the effects can then be adjusted individually for each input channel (microphone, keyboard, etc...) on the soundboard. This means you could put a lot of echo on one guys vocals while adjusting another guys to have almost none. Now that we have examined the concept, here's how you plug it all in:

Multiple Effects

You will probably want to run several different effects at the same time. This can be done by either using a multiple effects unit that will run many effects simultaneously within a single unit, or by putting several different effects units in line within the same effects loop. "In line" simply means hooking them up in a row such as in the following example.

Example 3a:



In this case the signal flow is coming from effects send and flowing toward return. Remembering that the inputs are always on the upstream side of the flow, the "inputs" in this situation will always be coming from the effects send jack, and the "outputs" will always be going toward the effects return jack. Thus we have a signal path like this:
Effects send (from the board) to Input (on the delay) to Output (on the delay unit) to Input (on the Reverb unit) to Output (on the reverb unit) to Effects return (on the board).

The Multicore



The PA multicore is used like an extension cord that connects all of the things on and behind the stage to all the things the sound man will be using in the sound booth on the other side of the room. The multicore should have at least as many low impedance (low Z) channels as your soundboard, and at least 2 to 4 high impedance (high Z) channels depending on whether you are running a stereo setup or not. When setting you system up this way, the soundboard should be placed at least 20 feet or farther out in front of the main speakers so that the sound engineer will be far enough away to get a clear idea of what is coming out of the system. The on stage end of the multicore will be a big box with individually numbered High Z inputs and Low Z outputs. The end of the multicore toward the sound booth will have high Z outputs and Low Z inputs with numbers corresponding the inputs and outputs on the stage end. The ends toward the sound booth will be loose and look like the ends of microphone or instrument cords. To properly hook up the multicore, simply plug each of the loose low Z ends into the channel on the soundboard that corresponds with the number printed on that end, then plug all of your microphones on stage into their regularly assigned channels at the box end of the multicore. For instance, the loose end marked "1" should be plugged into input channel number 1 of the soundboard. Then, on the stage you can plug microphone number 1 into the number 1 input on the box end of the multicore thus assigning microphone number 1 to channel number 1 of the soundboard. The high Z inputs and outputs are there to provide an extension between the monitor outputs at the sound booth and the monitor speakers on the stage. To do this, simply plug one of the high Z loose ends of the multicore into the monitor output on the mixer, and then plug a cable between the corresponding high Z channel on the box end of the multicore and the input of the monitors located on the stage.

If I've kept your interest for this long I'm very appreciative. You may or may not be interested just is what involved in a large scale PA system. If so, read on. If not, I fully understand.

Crossovers

Up until now, we have dealt with PA systems that use a single amplifier to power a set of full range speaker cabinets. In addition to speakers and horns, these cabinets are equipped with internal passive crossovers. Basically, crossovers are little electrical devices that receive a fullrange signal and divide it into separate outputs of midrange frequencies, lowrange frequencies, and highrange frequencies. That way, the highs are sent only to the speakers designed for the highs, the lows are sent only to the speakers designed for the lows, and the mids are sent only to the speakers designed for the mids. Passive crossovers do this by dividing the signal after it leaves the power amp while active crossovers do this by dividing the signal before it gets to the power amps.
Passive crossovers (located inside full range speaker cabinets) are good in that they make it possible to provide a full range of sound using only one amplifier, but they are a little inefficient. Since all the speakers are working from the same source, the low speakers, which require more power, will tend to rob power from the higher frequency speakers and horns.
Active crossovers (plugged in-line before the amplifiers) are good in that they make it possible to power the mids, lows, and highs from different amplifiers. This way you can use a big super-duper amplifier for your lows, and use a smaller amp for the mids and highs. This is a much more efficient use of power, and it gives you the ability to acquire a much more powerful and full sound. The catch is that using an active crossover requires a lot more equipment and expense.
Using an active crossover in a system is sometimes called bi-amping or tri-amping. Below is an example of tri-amping the mains in a mono system. This is the sort of system you could expect to use at a large venue such as a large pub or club. You may also find this sort of system at many smaller outdoors shows, such as a football club event on the oval, or something of that nature. The system will have nowhere near the impact outside as inside, but is necessary for the spreading of the sound as elements like wind can play havoc with the sound outdoors.

Example 4: Tri-Amping the Mains



With the exception of the signal path to the main speakers, example 4 is exactly the same as example 3. The effects loop and the monitor system should be connected in the same way as before, but now the mains have been turned into a tri-amped system. To do this, a crossover, three separate amplifiers, and three separate sets of speaker cabinets must be used. Each of these amplifiers as well as each set of speaker cabinets must be designated to a specific audio frequency. Which frequency goes where is determined by the outputs on the crossover. The "low out" should go to the input of the amp with the highest wattage because the low end speakers will require the most power, and the "high out" should go to the amp with the lowest wattage because the horns will need the least power. Just remember that it takes a lot more energy to vibrate the great big cone on a fifteen or eighteen inch speaker than it does to move the tiny diaphragm in a midrange horn.

Warning:
Never plug a high end speaker or horn into the amp that is plugged into the "low out" of the crossover. These speakers are not designed to handle such low frequencies and will be damaged very quickly if hooked up incorrectly.

To hook up the system in example 4, follow steps 1 through 15:
Monitors and Effects
1) Connect these together as described in example 3.
Mains (Keep in mind that even though the signal flow splits inside the crossover, it still flows from the mic toward the speakers)
2) Plug a high impedance cord into the main "output" of the mixer.
3) Plug the other end of this cord into the "input" of the main equalizer.
4) Plug another high Z cord into the "output" of the equalizer.
5) Plug the other end of this cord into the "input" of the crossover.
Lows
6) Plug a high Z cord into the "low output"of the crossover.
7) Plug the other end of this cord into the "input" of the highest powered amp.
8) Plug a speaker cord from each "speaker out" of this amp into the "input" of each low speaker (one cord to each speaker).
Mids
9) Plug a high Z cord into the "mid output"of the crossover.
10) Plug the other end of this cord into the "input" of the middle powered amplifier.
11) Plug a speaker cord from each "speaker out" of this amp into the "input" of each midrange speaker (one cord to each speaker).
Highs
12) Plug a high Z cord into the "high output"of the crossover.
13) Plug the other end of this cord into the "input" of the least powerful amplifier.
14) Plug a speaker cord from each "speaker out" of this amp into the "input" of each Midrange/high horn (one cord to each horn).
15) Take a break. That was a lot of work.

Below is an example of a large stereo tri-amped PA system.

Example 5: The Works



Now we are talking. This is about what you'd expect from an Entertainment Centre gig, or the Big Day Out. Just add more speakers and wattage of the amps. Also, in those situations, the monitors may have a separate desk almost comparable to the main desk and will be operated by a separate engineer. Generally that engineer will operate this desk from the side of the stage so the band members can easily communicate to him/her what they require from their monitor mixes throughout the show. Having said that, to keep it simple the components of this system are discussed below without a separate monitor desk to keep things relatively simple.

With the exception of the compressors, the additions incorporated into this system are simply a doubling of the system components covered in previous examples. At this point, you should have a pretty good grasp of how to hook it all together, so rather than listing a lengthy step by step, I have listed a brief description of each addition included in this example.

Two Monitor Mixes
Running more than one monitor mix can be very useful in that you can provide different monitor mixes for different parts of the stage. I have found that the drummer often wants to hear different things in the mix than the rest of the band. With two different monitor mixes, this is easily accomplished. Simply assign one monitor mix (channel A) to the drummer and another (channel B) to everyone else. This way you can adjust what the drummer hears independently of what everyone else on stage hears. In order to do this, your soundboard needs to be equipped with more than one monitor channel. These channels, usually designated as "Monitor A" and "Monitor B", will be controlled by separate knobs and will have separate outputs which must in turn be hooked into separate equalizers, amplifiers, and speakers.
Multiple Effects Loops
The same concept applies to the effects loops. To hook up two effects loops in a mixer that is equipped for it, all you have to do is run one loop through "Effects A" and another separate loop through "Effects B". Some boards come equipped with several different available effects loops that may be labeled "Effects 1", "Effects 2",etc. Sometimes the effects will be labeled as "auxiliary". You can run as many separate effects loops as your mixer is equipped to handle provided that you have enough separate effects units to pull it off. One possible use for this set up is that you could assign nothing but a long delay (echo) to Aux 2 and your general effects to Aux 1. Then when a song required a long echo on a certain part, all you would have to do is turn up the slider or knob for Aux 2 to get your desired echo without changing to rest of the effects at the same time. Then when the echo wasn't needed anymore, you could simply turn the Aux 2 all the way down effectively removing that effect from the mix.

Note: The effects send, monitor out, and auxiliary out channels are essentially nothing more than specifically labeled line out channels. This means that as long as you pay close attention to where you plugged things in and you properly re-label your knobs, you can use them interchangeably. Usually, the only reason to do this would be to acquire another monitor mix in a board that is equipped with only one monitor channel but has an extra unused auxiliary channel. To avoid confusion, I would recommend doing this only as a last resort. Also, don't forget that in order for your effects to work, they must return to the soundboard to complete the effects loop.

Mains in Stereo
Running two separate channels for the mains is what is known as running a stereo PA system. To do this, you need a stereo mixing board. This board will consist of two output channels for the mains. These will be labeled either "left" and "right" or "A" and "B". The sliders for each input channel on the board will control both channels simultaneously, but there will be a "pan" knob above each that will allow you to pan the volume from left to right just like the "balance" knob on your car stereo. The output sliders on the board will operate the outputs for channel "A" and "B" independently of one another. Hooking this system up is essentially the same as what you did when hooking up two monitor mixes. Simply run the left channel "A" out to it's own equalizer, crossover, amplifiers, and speakers, and then do the same for the right channel "B". This is where those stereo (two channel) components come in handy. For instance, you can hook the "left out" from the board into the channel "A" input of the equalizer and hook the "right out" from the board into the channel "B" input of the same stereo equalizer. This principal can be followed all the way through the crossover, and the amplifiers.

Note: When using a stereo amplifier in this way, make sure the switch in the back is switched to "stereo" mode.

Compressors
Compressors are an effect that is usually run in-line in the main signal path. They make a subtle change in the sound of the entire system that amounts to "taking the edge off". There are a lot of technical descriptions for what they do, but my best description is to say that they do just what the name implies. They squash (or compress) the sound together to create a more compact and clean sound. Be careful with these, they can be used for either good or evil. Set to a moderate level, they can add to the quality of your overall sound, but set too high, they can take the life right out of your performance.


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