Advanced Compression – The Attack Control (Part 1)

The skillful and deliberate use of compression in the mix process is something every engineer worth his or her weight in salt has a knack for.  While some grasp the basic concepts of compression relatively quickly, many engineers readily admit that the nuances of compression can take a little longer to master.

So if you are comfortable with the idea of using compression to control dynamics let’s take a look at some more nuanced concepts and applications of compression, starting with the humble ‘Attack’ control.

Using The Attack To Create Depth

In addition to its day job as a ‘dynamics controller’ most compressors can also be used to create subtle levels of depth, adding dimension to a mix.  In fact the skillful use of the attack control can turn compression into a form of reverb.  Let me explain.

All sounds have a volume envelop.  This envelop is made up of the attack (or beginning) of the sound, the sustain, the decay, and release.  Percussive instruments, like snares and bass drums, usually have a well defined attack, with relatively short sustain, decay and release times.  Keyboard instruments can have well-defined attacks, with longer sustain, decay, and release times.  Strings instruments can have longer attack and sustain times, with medium to short decay and releases.

As a general rule, the more defined the beginning of a sound (professionally know as ‘the transient’), the more ‘present’ or ‘forward’ the sound is perceived as being by the listener.  The converse is also true, the less defined the transient, the greater chance the sound will be perceived as being further away from the listener.  By shaping the transient of a sound you can therefore cause the sound to be perceived as closer to you or further away.

Listen For Yourself 

Take a listen to the clip below.   Clip 1 is an OH Drum track with no compression.  Listen to the transients of the HH and snare in particular.  They are crisp and defined.

Clip 1 – Overhead Drums (No Compression)

Now listen to Clip 2.  Clip 2 is the same clip but with a Fast Attack engaged  on a SSL Channel strip.  Once again pay careful attention to the transients of the HH and snare.  How do they compare with Clip 1?  Is the snare in this clip in the same position or is it further forward or further backward than the uncompressed snare in Clip 1?

Clip 2 – Overhead Drums (SSL Channel Fast Attack Compression)

When comparing Clips 1 and 2 the differences are extremely subtle but definitely noticeable.  For example the transients in Clip 2 lack the crispness and definition of those in Clip 1.  The snare in particular is also noticeably further back from the listener, lacking the presence and forwardness of the uncompressed snare in Clip 1.  Notice also the perceived size of the drum kit and room in Clip 2.  With a fast attack setting the drums and room seem larger!

Softening Sound

These clips reveal another interesting feature of a fast attack setting on a compressor.  When in use not only does a fast attack setting push a sound further back into a mix, it also has the effect of ‘shaving off’, ‘softening’ or ‘blurring’ the transient of a sound.

A fast attack setting can therefore be used to take the edge, presence, definition and bite off of a sound which has the effect of reducing the perceived presence of the sound, pushing it further back into a mix.  In fact fast attack settings often do all of these things at the same time!

Training Your Ear  

Below are some additional examples of a fast attack setting in use.  Whilst these examples are subtler than the first two clips, by listening to the transients and comparing the uncompressed with the compressed versions, you can hear how a fast attack can be used to achieve anything from taking the edge off a sound (as is the case with the bass in Clip 6) to noticeably pushing a sound further back in a mix.

Clip 3 – Snare (No Compression)

Clip 4 – Snare (SSL Channel Fast Attack Compression)

Clip 5 – Bass (No Compression)

Clip 6 – Bass (SSL Channel Fast Attack Compression)

At this stage we’re not making a value judgement as to whether the compressed or uncompressed clips sound better – we’ll touch on that in the next part!  We’re simply training our ears to hear what a fast attack setting on a compressor can do to a sound.

Build Your Own Compressor

In Part 2 of this article we’ll look at creative reasons and ways to use a compressor’s attack control in the context of a mix, but for now I have a little challenge for you!

Imagine you have been commissioned to build your own compressor.  Rather than label the attack control ‘Attack’ as many compressors do, you decide to come up with your own term for ‘Attack’ based on what you perceive the attack control actually does to sound.  What will you call it?  The ‘Presence’ control?  Or ‘Forward’ knob?  Or maybe something else entirely?  What will you call it?

Until next time I’d love to hear your thoughts, comments and discoveries in the comments section below!


[NB: Audio clips are from the ‘Where It All Comes From’ mix session available exclusively for Mixcoach Pro Members at  MixCoach Member!]

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