Thứ Tư, 5 tháng 10, 2011

Setting Up A Sound (P.A.) System

Setting Up A Sound (P.A.) System
The most common question I get asked by professional singers is, "how do I set up my P. A. (public address) system to achieve a good sound?"

It saddens me when I hear a singer with a good voice and well produced backing tracks have their performance ruined by a poor sound caused by their lack of knowledge on how to set up the sound system.
It also saddens me when I hear a performer who has never bothered to learn how to sing but tries to rely on the best equipment and engineer to try to make their voice sound good.

I have held many classes to relieve the stress and teach singers how to accomplish the best sound from their equipment.

Here are some easy steps to setting up and getting the best sound from your P. A. system.

When a singer becomes professional and has to set up a P. A. system, they find it quite stressful but it doesn't have to be like that.
You should learn to sing properly in order to get the best quality and projection from your voice without incurring damage, taken care of your image so that you look as well as sound professional and worked on how to talk to an audience and interact with them so that you give your best performance.

If you plan to work self contained you will need to know how to set up the P. A. system and be your own sound engineer and even if you are going to work somewhere where you have the luxury of a professional sound engineer, it will benefit you to know the basics of how to set up the P.A. system.

Once you have purchased all the necessary equipment, it's now time to set up for the gig and for the purposes of this explanation I am going to use the following equipment:

1. Soundcraft spirit 600 powered mixer
2. Electrovoice stage 200sx speakers
3. shure SM58 microphone
4. apple ipod (for playing backing tracks)
5. peavey powered monitor
6. one set of speaker stands
7. connecting cables
Speakers and Stands
The speaker stands should be placed at the front of the stage or performing area, at either end and when the speakers are mounted should be at a height of 2ft above the head height of the audience.
This is to prevent the sound from being blocked by people standing in front of the speaker and also prevent hearing damage by someone passing the speaker.

The singer should not be in font of the speakers as this can cause problems with feedback.
Feedback occurs when there is an audio loop generated between the microphone and the speakers, caused by the microphone picking up the sound from the speakers and playing back through the system.
Feedback sounds like a high pitched squeal which is not pleasant to listen to and is the biggest contribution to speaker damage.

I have decided to use a powered mixer in this example as there is less equipment to contend with.

I usually find that singers feel daunted when they first encounter a multi-channel mixer, however once it is broken down into the various sections it becomes clear that it's not too difficult to master.

Whether a mixer has only one channel or twenty one channels makes no difference as each channel is just a copy of the first channel to allow more instruments etc.

The mixer is where all the sound from instruments, microphones and audio players are connected in order to mix the sound with equalization (EQ), effects and volumes before it goes to the amplifier and speakers and if we look at the picture below we can see the various parts.

1. Channel Input 2. Trim 3. Channel Volume 4. EQ 5. Channel Effects 6. Master Volume 7. Master Effects
8. Master Outputs

powerstation 600 mixer
The channel inputs (1) comprise of balanced inputs (three pin xlr type) are for microphones and the unbalanced (1/4 inch jack) are for instruments.
The trim control (2) allows you to alter the input gain for each channel. As different instruments and microphones have different output levels it is important to trim each channel to get the best level without distortion.

The channel volume fader (3) allows you to balance the volumes from each channel.
The EQ (equalizer) controls are where we can add bass or treble to each input.
We can simplify this by thinking of your hi-fi system where you can change the mix to obtain the desired sound.

The (high) control adds or subtracts top end (treble) EQ to the sound.
The (low) control adds bottom end (bass) to the sound.

The mid-sweep is made up of two controls working in conjunction with each other and allow you to choose a frequency with one control knob and then boost or subtract the chosen frequency with the other.
The channel effects allow you to add effects such as reverb or delay to the channel to make the sound of a microphone more spacious.

It should be noted that the more reverb added to a microphone makes the sound more distant and unnatural, therefore it should be used sparingly.

The master volume controls (6) allow you to set the overall volume of the P.A. system.
The master effects (7) also s you to set how much effects gets sent to the channels.
The master outputs (8) is where you plug in the cables going to the speakers.

The manual for your chosen mixer will give you more in depth instructions on how it should be used however let's look at the basics which will get you on the road to a good sound.
You should have the speakers placed properly and the mixer within easy reach of your working area.
The mixing desk should be set "flat" (all volume faders and trim controls at zero, EQ and pan controls centered).

You should have your backing tracks player connected to two channels (e.g.. 1 and 2) and your microphone into another channel (e.g.. 3)

Play one of your tracks (preferably a powerful upbeat song) and turn up the trim for the two channels until the led lights on the meter read just below 0db.

Now turn the master volume up to the 0db mark and then turn the channel volumes up to a comfortable level.
Go out in front of the speakers in order to hear the sound properly and listen to the track.

You should be listening for clarity and how much bass or treble are prominent.
Go back to the desk and add 3db of high EQ to both channels and then go back in front of the speakers and listen. If the sound is too thin turn the top down slightly.

Now do the same with the low EQ. You should be aiming for a good balanced sound which is clear and has a good bass sound.

Turn the pan of channel 1 fully to the left and channel 2 fully to the right. You should now have a stereo sound coming from the backing track.

Switch the track off and now follow the same steps for the mike channel (the pan should be in the center position).

Be careful when going in front of the speakers that you don't encounter feedback.
Now play the track and sing while adjusting the volume of the microphone channel to match the backing track.

Your voice should be heard just louder than the track and if it doesn't stand out from the track you can use the mid sweep controls in the following way to help give more definition to your voice.

Set the frequency of the mid sweep on all three channels to 4kHz.
On the microphone channel boost this with the dB knob by 1 to 3dB and subtract 1 to 3dB from the backing track channels. This should make your vocal stand out more without the need to increase the volume.
Stop the track and add some reverb or delay to the mike channel.

It's important to note that if you add too much effect to the microphone you will sound more distant and unnatural. It's a case of less is more.

If you decide to use a separate mixer and amplifier then It is a simple case of taking leads from the outputs of the mixer to the inputs of the amplifier and connecting the speaker leads to the outputs of the amplifier.
I would advise that the power from the amplifier is greater than the power rating of the speakers.

The reason for this is to leave some headroom within the amplifier thus reducing the risk of overdriving it and sending a distorted signal to the speakers.
For the purposes of this article I am using the shure SM58 microphone.
It is reasonably priced and used by many of the worlds top vocalists.

There are numerous makes and types of microphone on the market and they are all down to a singers preference.

It is advisable to educate yourself on this subject and try out as many different microphones as possible before deciding on any particular one.

You will need a monitor (foldback) system in order to hear what the audience are hearing and for this article I am using a peavey powered monitor, which should be placed at the center of the front of the stage facing the singer.

Most mixers have a monitor output and it's just a case of connecting a lead from the output to the input of the monitor and setting the volume of the monitor.

Playing backing tracks.
There are many types of players for backing tracks and I will give some pro's and cons for each.

Pro's: Cheap to buy and easy to record onto.
Cons: Poor quality sound, they wear out, have to be rewound after use, prone to breaking

Midfile Player:
Easy to transpose keys, easy to transfer from computer, can sound good.
Cons: Only as good as the sound card within the player, floppy disks wear out and damage easily.

Mini Disc:
Pro's: Excellent quality, easy to record, no need to rewind, inexpensive to buy.
Cons: Discs wear out, have to change discs during a set.

Pro's: Great quality of sound, easy to manage.
Cons: They can skip with vibration

Pro's MP3's can be played fro an mp3 player or laptop computer, no need to change discs or tapes, excellent sound quality.
The apple ipod is an excellent player for backing tracks as you can store thousands of tracks without having to change discs or tapes and it is also easy to find songs using the jog wheel.

Cons: small screen can be difficult to read in poor lighting.

Connecting Cables should be of good quality and well looked after.
You should always carry spare leads, microphone, backing tracks and player for emergencies.