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Effectively Using Parallel Compression In Mastering

An overview on setting up and using parallel compression, as well as tips to get the best of this highly effective technique...

This chapter will teach you about a powerful way of using a single-band compressor – parallel compression. Outlined are some of the downsides to using standard single-band compression and how parallel compression can overcome these.

The chapter begins with what parallel compression is and how to set it up, then provides tips on how to get the best out of this incredible technique.

The compression technique demonstrated in part 1 (The Audio Mastering Blueprint) is technically known as downward compression. The compressor works by pressing down on the louder passages, creating more headroom above the peaks, in turn allowing for an overall increase in perceived level giving a fattened up effect.

The problem with compressing in this way is the very fact that the ‘louder passages’ are being pressed down, or squashed if you will, whereas the quieter passages remain relatively untouched. Just when the track needs some attitude or punch (when it has got loud), the compressor kicks in and squashes it down, reducing the impact of the transient hits. Wouldn’t it be great if we could flip this around but get the same result – so the quiet bits experience more compression, whereas the louder bits experience less?

The way to achieve this is by switching from downward compression to upward compression. This is where we compress from the bottom up as opposed to the top down. The way to do this is by setting up your compressor in a parallel fashion.

This article is provided by The Audio Mastering Blueprint

I’d now like to introduce you to parallel compression which is sometimes known as “New York compression.” This is an extremely useful technique; I probably use it about 80 percent of the time.

Its application is all the same situations as you would use a normal single-band compressor (bringing a mix to a whole for instance, giving it a layer of gel and gaining overall loudness) only this way of compressing is more friendly to the transient impact of the louder passages because it contributes most to the signal during the quieter passages instead.

Here’s how it works. In terms of set-up, it’s really simple. You have your signal split in two, one goes through your compressor and one goes around it to join back with the compressed signal on the other side.

One signal is wet (compressed), one is dry. Figure 1 shows a block diagram of how it may look:

Figure 1

Depending on whether your DAW has plug-in latency compensation, you may need to insert a sample delay plug-in into the dry signal to ensure both the wet and dry signals fuse back together in line with each other on the other side. This is to compensate for the delay caused by the processing time of the compressor plugin.

If this is the case, to set the correct delay time, feed a signal through the parallel compressor network and set the compressor’s ratio to 1:1 with the output at unity gain (0 dB), then reverse the phase of either the wet or dry signal.

In doing this, you will get silence at the output providing the wet and dry signals are perfectly in line. If not, adjust the delay plug-in by samples at a time until you get total silence at the output (two identical summed signals give silence when one’s phase is reversed). The set-up may look like Figure 2.

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Figure 2

Some compressors include a dry and wet parameter. By allowing an amount of dry signal through, you are effectively parallel compressing.

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