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Basics of Compression And How TO Use the Logic Pro Compressor With VoiceOver

Posted in effects, GarageBand, and Logic


Are you a blind musician or Audio engineer/producer new to using compression? Confused about how Apple’s Logic Pro compressor works with VoiceOver? This tutorial breaks down the most important parameters to pay attention to, with a bonus VoiceOver quit tip thrown in as well. Once you are done with this tutorial, this member tutorial goes a little more in depth on attack and release times and talk about some of the features not covered here like the built in saturation. Not a member, then join the band!

What is a Compressor?

We should probably begin by answering the question of what’s a compressor and better yet, why is it needed/what is it used for? Compressors are generally used to control dynamics, or put simply, to help level the audio out. It does this by pulling the loud parts down so that its closer in level or volume to the quiet parts. This allows the audio to sound more even or leveled. This is useful in a busy mix, where you have a-lot of elements and having each element leveled out helps it to be placed better in the mix.
For this example we’ll be using a Vocal. As you will hear in the example, the parts that are sung quietly can get lost in the mix. It also makes it difficult to set the volume fader on the track to the right level so that the vocals are heard fully through out the song because of how much louder the loud parts are over the quiet parts. Using a compressor, we can even out the dynamics, or the difference between the loud parts and the quiet parts, and once they are closer in volume; it’s a lot easier to find a place for them where they are always audible in the mix by adjusting the volume fader on the track.
Now you may be asking what about automation or region gain to even out the volume differences in the vocal? While Automation and region gain are useful tools, they only would take care of the leveling part. A compressor also imparts certain characteristics to the audio that can emphasize things. It can make it sound as though the singer is putting that much more emphasis on the words or as if the drum is being hit harder. Automation is more useful towards the end of a mix to fine tune the final levels of the track faders.

Getting Started With The Compressor

So now that we know the compressor is used to pull down the loud parts so that they are closer in volume to the quiet parts, the first thing that it’s helpful to know is where our track is peaking. Using the peak meter on the channel strip in the mixer, we can get a rough idea of the dynamic range. Put another way, seeing what the quietest part peaks at, vs the loudest part. The peak meter just lets us know what is the loudest our audio gets and only updates when a new louder value is reached. This info is useful so we can get an idea of where the compressor may actually start working on our audio.
Case in point, if the loudest part of the song peaks at -15dB but the threshold is set to -5dB, the compressor isn’t doing any compression then since the audio never crosses the threshold. Over time, as you start to hear compression better, this may not be as necessary a first step.
So speaking of threshold, this is the first parameter in the Logic compressor, and is probably the first one you will want to adjust as it will determine if and when the compressor will start affecting our audio. Whenever the audio crosses the threshold the compressor will act on it, and the compressors behavior is now determined by the other main parameters.
If the threshold determines when the compressor kicks in, the ratio will determine how much it does kick in. At a ratio of 2:1 (read as 2 to 1) for every 2dB your audio crosses the threshold, it’s turned down by 1dB. with a4:1 ratio, for every 4dB it crosses the threshold, it’s turned down by 2dB. And so on, and so forth.
So you can think of the relationship between the threshold and ratio this way. A lower threshold subjects a wider range of your audio level to compression, while a higher ratio causes a more drastic compression effect.

The different types of Compressors

One of the nice things about the Logic compressor is that it also has emulations of vintage analog compressors included. These are less trying to be accurate point for point emulations of these vintage classics, but more about imparting some of their tonal qualities and characteristics on your audio. Different compressors’, whether they were tube or solid state, colored the audio differently and some could be more aggressive or pronounced than others, vs some that may be brighter while others may be darker sounding.

The 7 Logic Compressor Types

  • PLATINUM DIGITAL: Logic Pro’s native digital compressor. The most transparent sounding of the bunch
  • STUDIO VCA:emulates the Focusrite Red 3 Dual Compressor/Limiter. Famous for maintaining a natural sound, even when pushing the compression hard.
  • STUDIO FET: emulates a 1176 Rev E “Blackface” Compressor/Limiter. Known for having an aggressive sound that delivers a sense of “energy.
  • CLASSIC VCA: emulates the DBX 160 compressors/limiters. it’s famous on drums, known to inject a warm and grainy punch to your sounds.
  • VINTAGE VCA: emulates SSL G Bus Compressor.
    Famous for cohesion and clarity on Submixes or the MixBus.
  • VINTAGE FET: emulates the UREI 1176 Rev H “Silverface” Compressor/Limiter.
    Famous for its character and punch. It’s aggressive sound delivers a sense of “energy
    emulates the Teletronix LA-2A Optical Compressor.
    Famous on Vocals for its smooth, natural, musical compression.


Attack And Release

Next we’ll take a look at the attack time. This determines how quickly audio will go from no compression to the compression amount determined by the ratio when the threshold is crossed. As this is in milliseconds, the smaller the number, the faster the attack.
The release time is the opposite. It determines how long it will take the compressor to go from compressed audio to uncompressed once the signal falls back below the threshold. Longer release times can add a sense of sustain as if notes are held longer etc. to vocals for example.

The Other Stuff

The Logic compressor has a lot more to it and is very full featured. For example there is some built in saturation, a limiter and both an internal or external side chain.
So As you can see, a lot more than we had time to get to in this tutorial. If you would like a deeper dive into the Logic compressor, remember you can follow up with this member’s area tutorial. To see how to dial it in on specific instruments, there is also the option to book a one on one training session. In the lesson we can load up a project you are working on and go over how to use it on the tracks you are currently working on. And if you are new to EQ as well, then check out this tutorial on the [basics of EQ./basics-of-eq-and-using-the-logic-pro-channel-eq-with-voiceover/)