Sunday, May 18

Audio Compression Tips for Mixing

Professional Audio Mixing is basically two steps: EQ and Compression. Different instruments require different compression scenario. To those that do not know what is compression. It is all about controlling the peaks of recorded signal.

The easiest way to understand how compression can be useful to a mix is vocals. Vocalist even professionals have tendency to sing very loud in some portions of the song. Now without compression, this vocal track could be very annoying. Compression sets balance by automatically compressing signals when it reaches a certain level.

My major rules in compression is simple, compression takes away signals and sound quality. It is a fact, that if overdo it will drastically reduce the power of the sound.

Now let me give you my tips on compressing common instruments in audio tracks.

Compressing vocals in the mix-----I use the presets of Sony Wave hammer-Voice settings. The characteristics of these compression settings are this:

Attack time- 5 ms
Release time- 50ms
Threshold- -10dB
Compression ratio - 5:1

Take note that attack time is very short, it is because vocals is highly transient in nature, the notes of the vocal is very short, so to capture effective compression in vocals, one must set to short attack time. The release time is a bit slow. It is because when a vocalist sings a loud portions of the song, it will tend to last a longer time also. It is an odd song to have a very short loud portion of the vocals. Threshold of the compressor is the the level of the signal at which compression starts. For vocals, i need it to set to -10dB because more than -10 dB in vocals is already very dominative in mix. The compression ratio is 5:1, this means a five times reduction in the signal when the it reaches -10dB or above. Now thats a bit compression to lower the volume of the loud peaks.

Compressing guitar in the mix : For acoustic and clean electric guitars, I use Sony wave hammer Guitar presets. The compression settings are:

Threshold: -20dB
Ratio: 5.0 is to 1
Attack time: 15ms
Release time: 15ms

The threshold is lower in volume compared to the vocals, the primary reason is that guitars need to sound a bit lower than vocals in the mix or else it will dominate the vocals. Compressing at -20dB ensures that any strong level above it will be suppressed five times to control the volume and not being too loud. Guitar sounds are not sharp transients in nature unlike vocals, kick and snare. It will have a sustaining and delaying sound. So a medium set attack and release time is good.

Compressing bass guitar the mix: Bass guitar sounds needs to be compressed to provide a steady beat backbone to the song. This is very important in modern rock and pop tracks. And because of this, I use Sony wave hammer Bass guitar presets with the following settings:

Threshold= -20dB
Ratio: 6 is to 1
Attack time: 40ms
Release time: 80ms

The main concept of creating a big bass sound, is slow attack and fast release. This is because since bass are not super fast transient it needs to develop it's level first then set compressor to attack the signal and release it immediately, the effect is a loud sounding bass. Compression settings is a bit higher than guitar and vocals, because bass needs to be more uniform in sound to provide a steady beat.

Compressing kick drum in the mix: I do not compress kick drum in the mix because I want to sound real, alive and not compressed. Compressing kick drums in my experience, takes away its deep bass sound so I do not like idea of compressing it.

Compressing snare drums - Snare drums needs compression, so to compress snare I use these settings:

Attack: 20ms
Release: 40ms
Threshold: -12dB
Compression ratio: 5:1

Snare needs to sound natural even though it is sharp transient in nature I prefer to compress snare with a slower attack time and faster release. This will give a full snare and powerful sound. Compressing with too fast attack time can flatten a sound and will make to sound dull.

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