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!]

15 Comments

  • Dave Stubbs

    Reply Reply June 10, 2013

    Hi

    Firstly thanks for providing the great site and content – It’s full of good clear ideas.

    However, this article leaves a bit confused. Doesn’t the softening of the sound depend on ‘how’ fast the attack is. I mean if I use an ultra fast attack time then shouldn’t the transient just pass through the compressor unaltered. So for example if I want to use a compressor to just even out the level of a bass guitar without altering the envelope I could use as fast attack as possible ( without it causing audible distortion) and a slow release time of about a note length.
    Then if I want to accentuate the transient more I can reduce the attack time to let some of the transient through? Or if i want to soften the transient would i use a fast attack and fast release so that the initial transient is compressed but the tail of the envelope is not compressed. Hopefully I’m making some kind of sense here – would appreciate your take on this

    Thanks

    Dave.

    • StoneWalters

      Reply Reply June 10, 2013

      Hi Dave! Sorry for the confusion! You are absolutely correct…the softening of the sound does indeed depend on how fast the attack is. The slower the attack, the more of the transient that passes through the compressor before it’s gain reduction mechanism kicks in. However when using an ultra fast attack the opposite happens – the transient doesn’t pass through unaffected by the compressor because it is ‘caught’ by the ultra fast attack and then reduced by whatever ratio the compressor is set to. In fact (as you point out) the attack setting on some compressors can be so fast that it goes beyond softening the sound to audibly distorting the transient, which may or my not be the sound you are after!
      Once again you are also right on the money and making complete sense with your example of a bass guitar! For me the idea behind this article (and the next Part) is to start thinking of a compressor not only as a dynamics controller, but as a way to achieve other mix goals. So for example using a fast attack may not be the best idea if you want to retain the punch and transients of a bass part. However imagine a scenario in which you want to make your bass part more solid whilst retaining the transients. In this scenario you might decide to create a parallel bass track and use a fast attack setting only on the parallel track to soften the transients and by so doing push the parallel bass slightly backwards, helping create the desired dimension, all while allowing the main bass part to present the necessary transient information so the bass cuts through the mix.
      Does this make any sense?

      Stone

  • Dave Stubbs

    Reply Reply June 10, 2013

    Great reply – thanks and that makes sense. So would i be right in saying that a fast attack slow release would soften the attack overall because whilst the both transient and tail get compressed, relatively the transient part gets compressed more so that results in a smaller transient relative to the tail (and therefore a softer overall note)?

  • StoneWalters

    Reply Reply June 10, 2013

    Hey Dave. Glad it made sense! If I understand you correctly I think the way to get a smaller transient relative to the tail is actually to have a fast attack and fast release rather than a fast attack and slow release. Let’s see if we can unravel it! OK..so…let’s say your transient level is peaking at 0dB and the sustain of your sound registers around -10dB before decaying. A fast attack setting would ‘soften’ the transient, taking it down to around say -15dB. At this point the transient would be -5dB quieter than the sustain of your sound (which is at -10dB). [SCENARIO 1 – SLOW RELEASE] Now if you had a slow release the compressor would hold the level of your entire sound there at around -15dB, effecting not only the transient but also the rest of the sound. [SCENARIO 1 – FAST RELEASE] However if you utilized a fast release, the compressor would ‘attack’ the transient (reducing it’s level to -15dB) and then return to normal before having a chance to affect the level of rest of the sound. The net effect of a fast attack and fast release would be transients at -15dB and the rest of the sound at -10dB. So we can see that the transient is now ‘smaller’ relative to the level of the rest of the sound.
    Does that make sense?
    Coincidentally this is a great way to accentuate the room sound on a drum recording. A fast attack and fast release means the ‘transients/presence/forwardness’ of the sound gets ‘softened’ while the decay (or room sound) is left unaffected because of the fast release. When you then level match (i.e. adjust the gain of the compressor) to compensate for the gain reduction, the room sound is now turned up and is perceived as louder relative to the ‘softened’ transient. Because the room sound is now louder the listener perceives a greater sense of dimension. By way of reference I used a fast attack and fast release setting on Clip 2 above to achieve this exact effect.
    I hope this helps but if I’ve misunderstood or confused the issue please let me know!
    Stone

  • Boy Dre

    Reply Reply June 10, 2013

    I might call it the “Shutter” like in a camera. More brightness when it is open longer, less brightness when it shuts faster.

    Here I am -> http://www.Facebook.com/1boydre

  • Tassy Sandor

    Reply Reply June 11, 2013

    Thanks Stone for the important topic and explanation.

    It is also useful if we look at it from another point of view:
    It warns us and helps to understand that adjusting any parameter in any plugin may have quite different “side affect” than the names of the knobs suggest. (For example using saturation may make the EQ line boosting and cutting at not expected places.)
    These side effects can help us, if we are aware of them, as this attack control you explained, and can destroy the sound or mix if we lack or just skip this knowledge.
    So these articles are very useful reminders as well.
    Tassy

  • Stone Walters

    Reply Reply June 11, 2013

    @Boy Dre. ‘Shutter’ – I love that! What a great way to see it!

    @Tassy. Great point Tassy. The more I listen to seasoned engineers in interviews the more I realize they seem to have the awareness you mentioned. They seem to understand, no doubt through putting in their 10,000 hours, the intended impact a parameter might have on a sound or mix, but also the side effects as well. For this reason I find it interesting when they use their tools to solve mix challenges in unconventional ways – reaching for a saturation plugin to EQ a sound for example rather than an equalizer, or maybe using a compressor as a ‘coloring’ box to affect the the tonal balance of a track rather than simply control dynamics. I guess one of the more popular examples would be when reaching for the trusty 1176 compressor. The bluestrip version is known to have a more present and mid range bite, whereas the blackface version has darker low-mid/low end saturation.

  • Dave Stubbs

    Reply Reply June 11, 2013

    Thanks for the detailed response – that’s confirmed my understanding and is how I see it.

    Look forward to the next installment!

    Dave.

  • StoneWalters

    Reply Reply June 11, 2013

    Hey Dave. No problem at all! If you have any other ideas or insights don’t hesitate to let us know.

    Stone

  • Laszlo Galosi

    Reply Reply June 17, 2013

    Great article Stone, thanks. I’ve been using this concept with SSL Channel comp so much on guitars and bass, without thinking of I’m creating so called depth and reverb. I was also being confused to memorize which release settings generate more sustain to the sound, but its so logical based on your bass example, mentioned above in the comments.
    I will definitely call attack, forward, and presence, and transients to, maybe the “‘transient control” is more expressive than the “attack control”.

  • StoneWalters

    Reply Reply June 17, 2013

    Hey Laszlo! Thanks for the comment! I also love the SSL Channel comp for it’s fast attack settings too. I particularly like the fact that you are limited to 2 options. So if one doesn’t sound right there’s only one other option to choose from.
    I have to say I also really love your relabeling of the Attack Control as the ‘Transient Control’. That makes complete sense to me. Love it!

  • Bill McDonald

    Reply Reply July 11, 2013

    thanks Stone, I thought this was awesome. I am one of those guys I guess which takes alittle longer to really understand the use of Compresson. I know the simple terms of Compresson, , but I really got alot out of your Video. Your Video is going to help me to Listen more carefully, and after watching your video, I now have an idea what I’am Listening for. I also are one that uses the SSL Channel Comp, I need to study more in terms of the Attack , and release, I know there are so Much more to them then what I know. thanks again Stone, I truely appreciate it. Bill McDonald

  • Stone Walters

    Reply Reply July 15, 2013

    Hey Bill. You’re welcome! I’m pretty sure that getting to grips with how compression sounds and how to make a compressor do what you want it to do will be a lifetime journey! I’ve heard so many engineer’s tell stories of the fact it literally took them years to be able to hear and understand what compression was doing to their audio. So if you are taking your time…you are in great company! Don’t give up! One day it may seem like you’ve figure it all out and then the next day everything is a mystery again…well at least that’s how it is for me! 🙂
    I noticed in one of your other comments that you use the SSL Channel strip frequently. You have great taste my dear sir! The SSL Channel strip is a great place to start – particularly when it comes to understanding what a fast attack does to a sound. Why? Because it only has two attack settings – Fast and Not Fast!!! So if you haven’t done this already I’d encourage you to pick a compressor (maybe the SSL Channel would be a great place to start) and learn what it can do inside out. Use it on everything!
    Once you’ve done this and can almost imagine what an SSL Channel strip would do to your sound before you turn the knobs add a second compressor to your toolbox. Then learn this one inside out, but this time compare what it does and how it sounds to the SSL Channel strip. This way you’ll be building up a really great working understanding of compression and the unique sound each compressor imparts to your audio.
    After you’ve taken the time to master your first and second compressors adding additional compressor to your compressor toolbox because a much faster process because you have trained your ears what to listen for.
    As always let me know if I can help in any way.

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