To wrap things up regarding compressors, I will offer 3 Dos and Don’ts as my final word for now. These are things to always keep in mind when working with compressors. Some may have been previously stated in an earlier blog post.
DO Avoid using extreme settings to begin with, if you are just trying to control the dynamics.
DON’T Add compression to every channel by default. Start off with minimal compression, and carefully choose where to add compressors.
DO Experiment with different types of compressors – hardware and software. There can be differences in how they sound. Compressors can and do sometimes sound different from one another.
DON’T Forget to bypass the compressor occasionally while setting to check the results.
DO Remember to balance the output gain so the level doesn’t change when engaged and bypassed. This way you can accurately compare before and after. Also, typically compression is added AFTER the mix has been balanced. So you don’t want to alter levels with either compression or EQ.
DON’T Be afraid to experiment. Some of the greatest sounds in the history of recorded music came from misused and abused compressors.
Today I’m going to go a little deeper into how compressors work. But first, I want you to do an experiment. This experiment will allow you to SEE what a compressor does. When I did this, things started to become a lot clearer for me. We have to listen differently when it comes to compressors. We are not listening for frequency, we are listening to dynamic changes (amplitude, loudness).
For this experiment it would be better to use a bass track. The reason for this is one, we ALWAYS use a compressor on a bass track and two, the reasons to use a compressor on a bass track is because we want to control the initial attack of a note and lengthen the sustain of the notes, as they fade out quickly. Try to use a track that has a regular-type bass line, not one that is super busy.
Find a bass track (or create one using a VI). If a virtual instrument is used, use one that emulates a real bass guitar, not something like a synth bass. What is needed is a sound whose initial attack is strong (loud) and whose note decays after the initial onset of the note, like a real bass. Also, the track will need to be printed. For this test to work we need an audio clip, not a MIDI clip.
Put a compressor on the bass audio track.
Set the ratio to something higher, i.e. 6:1. Set a fast attack, i.e. 3 ms; fast release, i.e. 18 ms.
Lower the threshold until the meter shows roughly 8 dB of gain reduction. Then add some makeup gain. Set this to the amount being reduced. If the gain reduction meter shows 8 dB of reduction, set makeup gain to 8 dB. This way the volume remains the same.
What you should start to notice is that the initial attack of the notes (when the player first strikes the notes) no longer punches. Now the dynamics are a little flatter, smoothed out. The second thing you should notice is that the notes are more sustained. You will no longer hear the decay, but a nice solid note that holds out for it’s full duration of note value (i.e. quarter note, half note, etc.)
NOW, print the track again with the compressor engaged. What you should have are two printed bass tracks. One without compression and one with compression. Look at the differences between the two. The first track has a pronounced attack with high amplitude and fast decay. The second, the initial punch is now all or mostly reduced and the sustain of the note stays strong longer. Below is a picture of what this should look like.
I have done exactly that here. I used an Instrument track with Trillian Bass module – played a bass line – printed it – ran compressor with 6:1, 3 ms attack, 18 ms release, 8 dB gain reduction, and 8 dB make up gain. I think this helps to drive home what a compressors job is. In this example my goal with the compressor was to lessen the attack and give it more sustain. If you want to see what the compressor does even more obvious than this, use the fastest attack possible, with 8:1 ratio, with a lower threshold for more gain reduction (10 dB).
I hope this helps – it did for me! Next time I will start to go into specific parts of a compressor, i.e. threshold, knee, attack, release, etc.