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We will be looking signal processors. Signal processors play an important role in shaping the live sound into a polished, professional sound. But when they're overused they can easily destroy the power and intelligibility of a good mix. Also when they are used tastefully and musically, they can add a powerful dimension, supporting the communication of the heart and soul the musicians are trying so hard to portray.
There are two overriding categories of signal processors
Dynamic processors alter an audio signal based upon its frequency content and amplitude level. The more general limiting and compression on the system function to control the mix audio and to protect the speakers and the audience against peaks and audio surges. Individual dynamic processors provide a different function. They function to decrease the dynamic range of the audio source.
Dynamic range is simply the distance in dB from the loudest to the softest portions of the track. The true effect of the dynamic processor, when inserted into the channel signal path, is to reveal portions of the audio source at the lowest levels. The fact that the level control circuit turns down the loudest segments is somewhat incidental in itself as the value of the process is been seen when the signal is turned back up to regain the lost level.
Once the signal is turned up, the nuance in the audio source is revealed by the amount of the make-up gain. Words and notes that would have been buried in the mix without the compressor are heard clearly as a result of the compression procedure.
The compressor is an automatic volume control that turns loud parts of musical signal down when they exceed a certain level. The circuit that actually controls the level is the voltage controlled amplifier (VAC), the digitally controlled amplifier (DCA) and other externally controlled amplifier circuit. Because an audio waveform is an alternating current with changing amplitude overtime is essentially voltage. The amplitude can be used to trigger the amplifying to adjust in direct correlation to the energy level.
Imagine listening to a mi and every-time the vocal track starts to get too loud and read too hot on the meter, you turn the fader down and then backup again for the rest of the track. That is exactly how a compressor works. When used correctly, compression doesn't detract from the life of the original sound. In fact it can be the one tool that helps life and depth to be heard and understood in a mix.
Dynamic processors are typically inserted into a channel. The output of the processor, when patched into the channel return, supplies the dynamically altered signal back into the channel signal path and it becomes a permanent part of the of the sound from that point. It is also common to patch a source directly into a dynamic processor before it reaches the mixer.
some engineers use a lot of compression and limiting; other engineers don't use any. In commercial music, the use and overuse of dynamic processors is common, especially in the recording world. Because commercial recordings use compressors on many of the mix ingredients and because the mastering process often overuse peak limiters in order to achieve a polished sound.
N/B:- The dramatic differences between a recoding mix and a live mix is the feedback. These is to say that if a live sound engineer used the same amount of compression as the recording engineer, feedback would be extreme even among the best and most finely turned sound system.
There are five controls common to most compressors and these five controls are;
And once you know how these works you can operate any compressor, anywhere, any-time and to make it even better, these controls are easy to understand, and they do just what they say they do.
Increase in amplitude also brings about increase in voltage. The threshold is the point where the compressor begins to recognize the signal amplitude. Once the compressor recognizes the signal when the amplitude rise above a certain voltage, it begins to act in a way that is determine by the attack time, release time, and ratio controls.
One way boosts the signal up into the threshold. Picture yourself in a room with an opening in the ceiling directly overhead. You represents the signal, with your head being the loudest sounds and the opening representing the threshold of the compressor. Imagine the floor moves up and you begin to go through the opening. That's the way most compressor moves signal into the threshold by turning them up until it goes through the threshold.
The other way compressors deal with the threshold is by moving it down into the signal. Imagine yourself again in the same room, but this time the ceiling is moving down until you're through the opening. This is the other way the threshold control works.
N/B: The signal level stays the same but the threshold move down into the peaks.
But no matter which way the threshold works, it's the part of the signal that exceeds the threshold that is processed. Once the signal is through the threshold, the VCA turns down just the part that goes through leaving the rest of the signal unaffected.
The attack time controls the amount of time it takes the compressor to turn the signal down, once it has passed the threshold. If the attack time is too fast, the compressor will turn down the transients. This can cause the instrument to lose life and clarity. On a vocal, for instance, if the attack time is too fast, all of the ''T'' and ''S'' sounds will start to disappear. And on the other hand, if the attack time is too slow and the vocal is very compressed, the T's and S's will fly through uncompressed and sound exaggerated.
N/B: Variations in the attack time setting help to diminish or accentuate the relative attack of instruments such as guitar, bass, piano, or drums. Long attack times adjust average levels; short attack time adjust peak levels.
Release time is the time it takes the compressor to let go, or turn the signal back up once it's below the threshold. The release time might be as fast as 50 ms or as slow as five seconds.
Fast release times work well with fast attack times to control peak levels
N/B: Long release time with severe compression can result in increased sustain.
And also for a natural and unobtrusive sound, set the attack time relatively fast and the release time relatively slow.
Once the compressor starts acting on the signal, the ratio control determines how extreme the VCA action will be. This simply means that the ratio is simply a comparison between the level that goes through the threshold and the output of the VCA which is expressed mathematical ratio (11:1, 2:1 and so on). The first number in the ratio indicates the number of dB of input increase will result in 1 dB of output increase.
The output level control makes up for the reduction in gain caused by the VCA. If the gain has been reduced, the output level control is used to boost the signal back to its original level.
Ideally, the end result of compression is that the loudest portion of the signal sounds about the same as normal, but the softest portions seem louder.
Thanks for reading
Signal processor basics
Dynamic processors
Vocial compression
