Compressors, limiters and gates, and all the facts and fiction that surrounds their functions and uses.
It seems that there is always confusion surrounding the use of dynamic effects and what they do. By dynamic effects, I am referring to compressors, limiter and gates. The rookie home studio owner (myself was no exception) is always debating whether there is a need to invest in one of these units and how it actually helps your sound. My goal here is to give you a brief description of what these units do and how it affects you recordings.
Compressors are built to level out inconsistent sound sources such as a voice. How it does it is simple, each compressor has these basic controls (or, most anyway)...Threshold, Ratio, and Output. The "Threshold" sets the level at which you want to start compressing the signal, the "Ratio" sets how much you wish to compress (2:1 ration, 4:1 ratio, etc.) and the output just sets the level of the outgoing signal, the cool benefit of this output is that it also raises the quieter parts of the recording, so you not only lower the peaks to stop clipping, but also raise the soft parts, so it gives you signal an even, consistent level. That is one of the reasons it is so useful on vocals...it makes the signal more even and easier to work with.
When the signal enters the compressor it reads the level of it, and if it hits the threshold, it then starts to compress the signal, therefore, if you have set a 3:1 ratio on a -2dB threshold, when the signal gets within 2 dB of clipping, it starts to squash the signal down at a 3:1 ratio. So, for every 3 dB of level, the compressor only sends 1 dB more to the mixer, or PC, or whatever you are sending it to.
Limiters do what a compressor does only at the threshold, instead of compressing the level it stops it. So it is to protect the signal from clipping regardless of dynamic impact on the sound. It is sort of like a compressor at about 100:1 ratio:-)
A very good use of these two effects together is obvious...set your compressor at a nice safe setting to softly compress any signals that appear to be getting out of control, then, after the compress run the signal into a limiter that will stop the signal dead at the level of clipping. This will allow you to get the most dynamics out of your original signal plus protect the recording by setting a hard limit on the overall output level.
The gate seems to be the most confusing for those new to recording and in reality, it is the simplest little piece of gear in the world.
The gate has a setting that is similar to the threshold setting of the other two we discussed, the difference is how it is used. What the gate does is keep the microphone off until it hears a signal at the level you have set, it then opens the gate and lets the sound through. You may be wondering how this helps you at all...say you are recording a drum kit with a mic on the snare, kick, and toms. What you can do is run each mic through a gate and set it so that the mic on the snare will open up as soon as it hears the snare hit, but, if it hears the toms get hit, being farther away from the snare, the signal will be quiter and not open the gate so only the snare sounds get through the snare mic.
This is, of course, not a perfect answer, because once the gate is open, all sound gets through it regardless of where it is. Gates do help in separating the drum sounds for later mixing and processing tho...
I hope this has helped you understand the form and function of these effects. I did not intend for this to be an in-depth tutorial, just a brief note to help the new home recorder understand what these effects do and how they do it...
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May 22, 2004 03:16 am
|Wow I understand this.
Excellent article for me. Have just purchased a Yamaha multitracker and I am dumbfounded by the various effects and signal processing. I am not the most technically minded person and this was concisely explained.
Jun 18, 2007 01:26 am
expanders fall into this category aswell....it's basically an upside down compressor...where everything past the threshold is raised in level...mastering engineers use this to compensate for overuse of compression.
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