Wednesday, 10 April 2013

Basic PA System Setup

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Basic PA setup

An easy way to remember the signal direction (whether to plug your equipment into inputs or outputs), is to remember that anything traveling from the direction of your microphone into the mixer should generally be plugged into the inputs of the mixer, whilst anything traveling out from the mixer (to the speakers/monitors etc.), should generally be plugged into the output. Always remember the amplifier/mixer as the central piece of equipment, and you shouldn't go far wrong.

  1. Firstly, make sure all plugs are removed from sockets and power is off.
  2. Plug the end of the microphone cord into the input socket of the mixer (input line 1 of the mixer could be used). There may be two alternative input jacks - a standard jack plug or XLR connection. Many corded microphones have the XLR type connection, however either of these connections will suffice for a basic setup.
  3. Plug one end of the speaker cable into the output socket of the mixer/amplifier. The speaker outputs are frequently found at the back of a mixer.
  4. Plug the other end of the speaker cable into the input socket on the rear of the speaker.
  5. Repeat steps 3 and 4 with the speaker cable for the additional speaker.
  6. Plug the amplifier/mixer into the mains.
  7. Switch on.
There we have it!  Your first PA setup.

PA setup including monitors

Monitors, although not suitable for every environment, should become an essential part of every professional musician's equipment. The reason for this is that on many occasions a vocalist or instrumentalist will be stood slightly behind the speakers. This makes it almost impossible to hear the clarity and sound that the audience is hearing. The performer does not necessarily want to hear the sound as loud as the audience, however the monitor relays an isolated sound to the performer, so he/her can easily distinguish the clarity, without too many distractions. For this reason, monitors face towards the stage and are are usually angled from the floor directly toward the performer.

The setup should follow the same as above, however if your mixer/amplifier has a monitor out socket, this can be used with a separate amplifier to allow independent controlling of volume levels to the monitors (N.B. you would want to hear sound from the monitors at a lower level than that of the main speakers). Many monitors have their own volume controls for this purpose. Powered monitors (monitors which have their own built-in amplifier), are available which avoid the need of a separate amplifier.

Common questions

Q. Why can't I keep connecting more and more speakers to make my system louder?

A. All amplifiers are designed to deliver their maximum amount of power into a certain number of speakers. This number is indicated (usually located near the speaker jacks) as impedance and is rated in Ohms (named after the man who discovered this electrical property). The most common amplifier impedance is 4 Ohms. This means that the amplifier will put out the most amount of power (be loudest) when it has a total of 4 Ohms worth of speakers connected to it. It will put out less power (be quieter) if the total of the speakers calculates to be more than 4 Ohms. The goal in any PA setup is to try and get the speakers to calculate up to, but not less than, the amplifier's rated impedance. If the speakers add up to less than the amplifier's rated impedance, the amplifier tries to put out more power than it was designed to do and may overheat and cause damage.

Generally speaking, the more speakers you add to your PA, the lower the impedance number becomes. This is why you cannot just add more and more speakers to make everything louder. Fortunately, most modern day amplifiers have built in protection to shut down the amplifier when it gets too hot. This is called load protection.

Q. What are the differences between microphones?

A. There are mainly two types of microphone used in a live PA environment :-
i. Dynamic microphones - Usually the most rugged, consisting of a coil that moves through a magnet field to introduce a small electrical signal (a similar principle to how speakers work). They tend to have a limited frequency response.
ii. Condenser microphones - now one of the most popular microphones. Although not usually as rugged as dynamic microphones, they usually have a broader frequency range, and require a power source to operate (either an internal battery, 'phantom power' as provided built-in by many mixers, or an external power pack).

Additional microphone info

iii. Uni directional microphones - often sold as 'cardioid', these are usually the most common, as they only pick up sound from an area in front, and around the front of the microphone. Omni directional microphones are rarely used in live vocal environments, as they pick up sound from all directions. They are however quite regularly used in 'interview' environments, where the microphone does not travel a great distance, and the pick up of surrounding sound is not an issue.

Q. Should I use a corded or cordless (wireless) microphone.

A. This is really down to preference, and the nature of your act. Generally speaking, if you tend to move forward of the stage by some distance, or do not like the idea of a trailing lead, then a cordless microphone may be more suitable. Bear in mind that if you have a limited budget, or do not tend to need a cordless microphone, then you will always get a much better quality corded microphone than cordless for the same price. Beware of very cheap cordless microphones - these are usually not suitable for anything more than home use. You really do get what you pay for with microphones.