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Foundations of Audio: Compression and Dynamic Processing
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Demystifying compression controls: soft knee vs. hard knee


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Foundations of Audio: Compression and Dynamic Processing

with Brian Lee White

Video: Demystifying compression controls: soft knee vs. hard knee

The kink in a compressor's transfer curve graph is known as the compression knee, due to its distinctly bent shape. The knee sits at or around the threshold point and represents how much and at what amplitude level the compressor will attenuate the signal. Some compressors allow us to change this knee from what is known as hard knee, or the full ratio of compression, as soon as the signal passes the threshold to what is known as soft knee, a more gradual form of compression where the signal is eased into the compressor's ratio setting over a larger threshold range.
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  1. 4m 56s
    1. Welcome
      1m 49s
    2. What you should know before watching this course
      32s
    3. Using the exercise files
      53s
    4. Using the "Get in the Mix" Pro Tools and Logic Pro session files
      1m 42s
  2. 13m 47s
    1. What is amplitude?
      1m 51s
    2. Measuring amplitude
      1m 57s
    3. What is dynamic range?
      4m 8s
    4. What are dynamics processors?
      3m 36s
    5. Hardware and software dynamics processors
      2m 15s
  3. 38m 40s
    1. Introducing compressors
      1m 45s
    2. Understanding threshold
      1m 29s
    3. Utilizing compression ratios
      3m 0s
    4. Understanding makeup gain and gain reduction
      3m 13s
    5. Understanding attack and release
      2m 12s
    6. Applying attack and release
      5m 22s
    7. Demystifying compression controls: soft knee vs. hard knee
      2m 43s
    8. Get in the Mix: Using compression to even out a vocal performance
      4m 55s
    9. Get in the Mix: Using compression to add punch and sustain to drums
      4m 39s
    10. Intelligently using compression presets
      3m 6s
    11. Recording with compression: Why or why not?
      2m 53s
    12. Recording with compression: How to do it
      3m 23s
  4. 18m 50s
    1. Introducing limiters
      1m 59s
    2. Types of limiters
      4m 17s
    3. Get in the Mix: Maximizing mix loudness with brickwall limiters
      5m 58s
    4. Solving common mix problems with limiters
      2m 58s
    5. Using layered dynamics processing
      3m 38s
  5. 26m 49s
    1. Understanding and using de-essers
      3m 46s
    2. Get in the Mix: De-essing a vocal track
      3m 30s
    3. Understanding and using gates
      4m 41s
    4. Understanding and using expanders
      1m 35s
    5. Get in the Mix: Gating a drum track
      3m 18s
    6. Understanding and using multi-band compressors/limiters
      3m 31s
    7. Controlling frequency content with multi-band compressors
      3m 3s
    8. Understanding and using transient shapers
      3m 25s
  6. 36m 38s
    1. Effectively using side-chain inputs
      2m 6s
    2. Using side chains creatively
      5m 4s
    3. Keying gates and compressors (and/or ducking)
      4m 12s
    4. Managing gain staging and headroom and fixing over-compressed tracks
      3m 20s
    5. Compression first or EQ first?
      2m 56s
    6. Understanding mix bus compression
      3m 26s
    7. Get in the Mix: Using mix bus compression
      2m 47s
    8. Get in the Mix: Working with parallel compression
      3m 46s
    9. Working with "modeled" vintage compressor/limiter plug-ins
      5m 57s
    10. Building healthy compression/limiting habits
      3m 4s
  7. 14s
    1. Goodbye
      14s
  8. 5m 51s
    1. A session with Brian Lee White
      5m 51s

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Foundations of Audio: Compression and Dynamic Processing
2h 25m Appropriate for all Dec 22, 2011 Updated Jan 10, 2014

Viewers: in countries Watching now:

In this first installment of the Foundations of Audio series, author Brian Lee White shows how to improve the sound of a mix with compressors, limiters, gates, de-essers, and other dynamic processors. The course explains the fundamentals of sound waves, and amplitude, explores common compressor controls, and shows how to eliminate unwanted noise using gates and expanders. The course also demonstrates best practices in compression and limiting in a variety of audio applications and covers sculpting the attack and decay of individual notes with transient shapers and applying frequency specific dynamics control with multiband compressors. Exercise files accompany the course and include special Get in the Mix session files.

Topics include:
  • Measuring amplitude
  • Understanding dynamic range
  • Introducing compressors
  • Utilizing compression ratios
  • Applying attack and release
  • Evening out a vocal performance with compression
  • Adding punch and sustain to drums
  • Using compression presets intelligently
  • How to record with compression
  • Solving common mix problems with limiters
  • De-essing a vocal track
  • Using gates and expanders
  • Controlling frequency content with multiband compressors
  • Using sidechains creatively
  • Keying gates and compressors
  • Fixing overcompressed tracks
  • Using mixbus compression
  • Working with parallel compression
  • Compression and limiting best practices
Subjects:
Audio + Music Mixing Music Production Audio Foundations Audio Effects
Software:
Logic Pro Pro Tools
Author:
Brian Lee White

Demystifying compression controls: soft knee vs. hard knee

The kink in a compressor's transfer curve graph is known as the compression knee, due to its distinctly bent shape. The knee sits at or around the threshold point and represents how much and at what amplitude level the compressor will attenuate the signal. Some compressors allow us to change this knee from what is known as hard knee, or the full ratio of compression, as soon as the signal passes the threshold to what is known as soft knee, a more gradual form of compression where the signal is eased into the compressor's ratio setting over a larger threshold range.

I say range because in a soft-knee compression curve, the threshold is no longer a single point on the graph, but begins and ends over a larger range of signal values centered around the original threshold setting, starting with a lighter ratio and working its way to the full amount as defined by the ratio control. Again, this concept is best represented by a transfer curve graph. Imagine a compressor with the ratio of 10:1 and a threshold at -20 dBFS.

In a soft-knee compression curve, the compressor would begin to attenuate the signal earlier, at around -30, with a ratio of 2:1. Maybe you're amping up to 4:1 at -25, 8:1 at -20, and finally reaching 10:1, just pass the threshold, at around -15 dBFS. On some compressors, the knee value will be a simple switch, allowing you to choose between a hard or soft compression curve, while on other compressors, this control may be defined in decibels, representing the threshold range over which the compression will ease into the full ratio.

Many compressors will not have this control at all and will either be fixed as hard-knee or soft-knee compressors or somewhere in between. For instance, the Dbx 160 doesn't have a knee control, but it's known for its over-easy soft-knee setting, which often sounds great on vocals and bass. As a general strategy, I like to use hard-knee compressors when I am working with the internal dynamics of a signal's envelope, especially on drums and percussion, like drawing out the attack of a snare or kick drum. The hard-knee transition at the threshold gives me tons of control over the signal's envelope.

Likewise, soft-knee compression is great on less percussive material like vocals, bass, and guitar, where you might not want to hear as much of an edge, but still have a nice firm signal sitting in the mix. Soft-knee compression can also work well on full mixes, where you're trying to subtly glue signals together without a lot of attitude from the compressor. So if you've never experimented with a compressor's knee, I think you'll find that it adds a lot of flexibility to dynamic control.

Find answers to the most frequently asked questions about Foundations of Audio: Compression and Dynamic Processing.


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Q: This course was updated on 1/10/2014. What changed?
A: The Get in the Mix videos have been updated to the most recent version of Pro Tools. Also, the course now includes free Get in the Mix sessions for two more DAWs: Logic Pro X and Pro Tools 11.
 
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