The world of band PA can be an extremely confusing one, with solutions ranging from £200 to £20,000, the key to the perfect set up is planning. Work out exactly what you need and add a bit extra and you should have a set up, that if treated well, should last a life time.

In the article I am going to cover the very basics of band PA, much like the band lighting article, the first few paragraphs may sound a bit simple for those who have some knowledge about audio, but I hope this will be a useful article for all.

The Very Basics

A sound system could be likened to making a smoothie, (bear with me on this one) whilst this may sound stupid is should allow you to visualise it much better. Lets begin at the very start of the audio chain, the microphone, I am not going to go into how microphones work as it would span hundreds of pages and be largely confusing. In our smoothie a microphone would be a fruit, you can get many different flavours of fruit each having its own flavour. With regards to a microphone each has its own specific application, there are mics for just about every application ever thought of, with the two main groups being vocal mics and instrument mics. Their uses being pretty self explanatory.

Next we have the mixer, which on first glance can look like an extremely confusing bit of kit, covered in hundreds of tiny little knobs and faders. However once the mixer is broken down you will see that the idea is a pretty basic one. Back to the smoothie... the mixer in this case is the smoothie maker, you can decide how much of each fruit will be in the final product. The mixer also has a second main feature, being the EQ (Equalisation), thinking about the smoothie, the EQ can add bits that the fruit (Microphone) is lacking. So if said microphone is lacking in bass and sounds too tinny then you can reduce the high frequency and increase the bass.

EQing again is a fairly complex topic and can be very in-depth, however I will keep it as simple as I possibly can, every mixer has a basic eq, with settings for High, Mid and Low frequencies, these will usually be in the form of knobs that turn ( pots ). There will usually be a knob for High, a knob for Mid and a knob for Low. With more expensive mixers having some more equalisation. When first setting up your sound system you will want these set to the "12o'clock position", pointing at 0 on the scale. This means that in the case of High frequencies nothing is being boosted and nothing is being reduced. When your sound system is set up, play a CD through two of the channels and have a play with the EQ and get a feel for the area in which each boosts and each cuts, it will really help in a live situation.

Anyway moving on, move about the mixer, most mixers will have faders to control the level and hence the mix out of the mixer, some mixers however to save space and cost will use a single pot instead of a fader. Some people actually prefer to use pots to faders, but this is just down to personal preference. In the smoothie scenario the settings of these faders will determine how much of each fruit goes into the overall drink.

On many boards two of the faders will be a different colour and will be labelled something along the lines of "Main Out", this controls the overall volume. With regards to the smoothie, once it has been made, the main out just controls how much you get (how loud the signal is that is fed to the amplifier). If you had set you faders on each channel and just wanted to increase everything then you would push the main out faders up.

Most desks have a similar layout and the following picture should help you visualise the placement of the controls on a desk.

Picture coming soon.

From the mixer there are now two possible places you could go, the first being a graphic equalizer then to the amplifier and the second being straight to the amp. Depending on how much control you need over the final sound, you will have to decide whether you need a GEQ.

I would recommend that if you are touring then a GEQ would be a good thing to get, it doesn't have to have lots of features, just a simple Graphic Equalizer will do perfectly. I would suggest a 15 band stereo one, as they do not take that long to set up. If however feedback (loud ringing caused by mics being too close to speakers) is a problem in most of the venues you play, a 31 band stereo EQ might serve you better. Setting up equalizers can be a pretty big task and hence this will be covered in another article. Graphic EQs are used to cut / boost frequencies in order to achieve the best sound possible. With the best way of visualising one, likening it to a mixer, with each "channel" controlling a different part of the overall sound.

Next up are amplifiers, these take your relatively quiet signal and turn it into a much louder signal that can be played back by loud speakers. When looking at amplifiers you will see that they have various ratings, usually being rated per channel at 4ohms and 8ohms. This resistance rating then pairs with the speakers, so say I had a pair of 4ohm loudspeakers, I would look at the 4ohm rating ( say 200watts per side) and from that I would know that my 300watt 4ohm loud speakers can be powered from this amp.

You can underpower speakers, this doesn't usually cause any damage, however going over the rated maximum output of the speakers can cause damage to the internal components of the speakers and render them useless, so be careful.

Now you know about Microphones and Mixers I'll be guessing that you want to know how to connect it all together and also learn a bit about the various interconnects available.

The Connecting It All Together

The main types of interconnects that you will come across are:

XLR - The un-abbreviated name for which is X-series Latched Rubber, but it will always be referred to as XLR. XLR's can be used for a huge amount of different things, but with regards to audio they tend to come in the 3 pin form. Buying XLR cables is usually easy, but you do not want to confuse audio XLR with DMX XLR cables which are for lighting and have a different resistance. XLR's tend to be used as a connection between the audio source and a mixer. They also get used between the mixer and EQ and then again between the EQ and the Amps. They also do get used between the amps and the loudspeakers but this is getting less and less common due to the introduction of speakon.

Speakon - Speakons come in 3 flavours (2 pole, 4 pole and 8 pole) with the 4 pole version being the most popular. Speakon cables tend to carry the amplified signal from the amplifier to the speakers, and since they are carrying quite a bit of power they tend to be thick.

Phono / RCA - Phono's tend to be used in the connection of stereo sources (CD Player) to the mixer.

Jack - Jack cables have a multitude of uses, with the two flavours being mono and stereo, with the names being pretty self explanatory. They get used all over the audio chain much like XLRs and can also connect the amplifiers to the speakers, but due to the fact that they don't lock into place, as Speakons and XLRs do, are also being phased out.

There are not many other interconnects available these days and hence I will just concentrate on using the ones above. Below are two diagrams, the first showing a very basic set up, and the second showing a slightly more complex one.

I hope to update this article on a monthly basis ,so please check back regularly for the next instalment.