Parallel Compression Explained (Best Practices & Mistakes)

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  • Learn about the technical reasons for using parallel compression.
  • Learn best practices for setting up parallel compression.
  • Discover ways to enhance your parallel compression.

Ever struggled with getting the right amount of punch in your mix? Compression is a great tool to combat this.

Your first instinct may be to place a compressor on a track and use it heavily. More compression should equal more punch right?

Not necessarily.

Aggressive compression often results in unnatural dynamics, which creates a lack of punch in your mix. This is because every part of your signal is nearly the same volume. Is there a way to add punch with compression while retaining your audio’s natural dynamic range?

The solution to this is parallel compression, which is also sometimes called NY compression. This process involves mixing the dry signal with the compressed signal. This allows you to push the compression further, knowing you can blend in more of the dry signal to keep things balanced.

How Does Using Parallel Compression Help?

Parallel compression gives you the best of both worlds. You can use the dry signal to retain the natural dynamics of your audio, while blending in the compressed signal to add body. With the right balance, you’ll end up with a punchy, natural sound that will take your mix to the next level.

What Exactly Does Parallel Compression Do?

To answer this question, let’s review the purpose of a compressor first. The goal of a compressor is to reduce the dynamic range of a signal. Dynamic range refers to the difference between the quietest and loudest part of a signal. So if the loudest part of a signal is found to be -5 dBFS, and the quietest is -17 dBFS, you would have a total dynamic range of 12 dBFS. When a compressor is applied to a signal, the loudest portions of the signal are turned down, therefore reducing the overall dynamic range.

Often when engineers use compressors, they want to reduce dynamic range without affecting the peak level of the signal. This is why nearly all compressors have a “make-up gain” feature. To go back to our example, if the peak level of your signal is -5 dBFS, but the compressor only turns the signal down by 3 dB, you could apply 3 dB of makeup gain to return the signal’s peak level to its original place. Problem solved, right? Not exactly.

(For a look at compression from the ground up, check out Understanding Compression (Audio Compression For Dummies))

The Problem With Make-Up Gain

While applying make-up gain does return the signal to its original peak level, in essence, the compressed signal has just been turned up in the mix. However, the compressor is still affecting the sonic character of the signal’s loud moments. While this is not always an issue, with an instrument like drums it may result in less punch due to the transients being compressed.

This is where parallel compression comes into play. Here we are splitting the signal into two paths, one compressed path and one uncompressed or “dry” path. Let’s say we heavily compress the signal so there is about 15-20 dB of gain reduction. No make-up gain is applied.

The loudest parts of the compressed signal will be reduced so much that they won’t add much gain to the dry signal when the two are combined. The quieter parts of the compressed signal won’t be compressed as much, if at all.

When the two signals are combined, the level will be greater than that of each individual track in these moments. This will create the perception that the track has been compressed. The gain of the quietest parts has been “raised” by combining the two signals, creating the effect of a reduced dynamic range.

As you can see, using parallel compression gives us the ability to keep the dynamic quality of the audio intact, while also allowing you to add the punch of heavy compression that you want in your mix. While it can be done on any instrument, this is especially why mix engineers like to use this technique on drums.

Leaving the dry signal in means that the engineer can keep the dynamics of the drums intact. Mixing the compressed version in allows them to add that extra bit of punch to the drums. This gives them a more natural punch than heavy compression on the dry tracks would.

Best Practices for Setting Up Parallel Compression

Now that we know what parallel compression is, let’s look at how to create a proper parallel compression setup.

Step 1: Create an Aux Send and Return Path

Parallel compression is typically set up using an aux send and return channel. To create this, go to the send section of a channel strip in your DAW and select one of the open sends (this might also be called a “return” depending on your DAW). Route the send’s output to a new bus.

A demonstration of how to route an aux send to a bus in Logic.

In a DAW like Logic, you can click on an open send, route it to a bus, and Logic will create the aux return track for you. The input of the track will be set to the bus you selected.

Pro Tools, unfortunately, doesn’t make it that easy. You can do this in Pro Tools if you select “New Track” when routing your send’s output. You can then route it to an “Aux Input” track, and Pro Tools will create the return track for you. The input will be set to the bus you have just created.

A demonstration of how to create an aux send and return path in Pro Tools.

Note if that if you are compressing a mono signal, create a mono return channel. If you are compressing a stereo signal, create a stereo return. Your DAW may or may not have this as an option but it’s something to keep in mind.

Step 2: Set the Send to “Pre-Fader”

Aux send pre-fader setup.

When setting up your aux send and return, it is important to make sure the send is set to “pre-fader.” This means that the signal going to your compressor is being sent to it before the signal reaches your dry channel fader.

Any adjustments you make to the dry channel’s fader will not affect the level going to the compressor.

This is important because if we were to make our send “post-fader,” any fader adjustments made on the dry channel will change the level going to the compressor, therefore changing the amount of compression applied to the signal.

Essentially, the settings created on the compressor will no longer have the same effect. Making this a pre-fader send will ensure that your settings are constant throughout the mix.

Now, you may be wondering what to do if you have to perform volume automation on a track? After all, no mix is static, and tracks often need to be turned up or down in different sections of the song. I would suggest that after you have completed steps 1 and 2, route the output of the two channels to another aux track, and label it something like “(Instrument name ) Volume.”

You can then perform any volume automation on this track. This will ensure that your parallel compression settings stay consistent no matter what adjustments you make in your mix.

Step 3: Adjust your Compressor Settings

Now that your signal path has been set up, you can begin setting the compressor’s ratio, threshold, attack, and release times. If you are going for an aggressive, heavily compressed tone, it’s best to start with a high ratio and low threshold.

There is no set amount of gain reduction you should apply, but aiming for 15-20 dB of gain reduction is a good place to start. If you’re going for something less aggressive, back off the ratio and threshold to apply less gain reduction. A somewhat slow release time should be used as well.

The attack time can be fast or slow, depending on the effect you’re going for.

A fast attack time will result in the transients of your audio being compressed. A slow attack will cause the compressor to engage some time after the transient occurs.

This can be useful when using parallel compression on drums, as it allows the transients to pass through the compressor untouched. It helps retain the punch of the drums, while still allowing the signal to be heavily compressed.

You can create a bus for your two tracks to do any volume automation.

Don’t forget to set your attack and release time to the tempo of the song

Doing this can help make the compression sound more natural. This way, the compressor is essentially engaging and disengaging in sync with the rhythm of the song.

The process for calculating the correct attack and release time is similar to calculating delay or reverb times. You can use free resources such as this to help you. Simply type in the BPM of the song and this calculator will generate times for a quarter note value, eighth note value, and so on. Eventually you will be able to do this by ear. The attack and release values you go with will, again, depend on the effect that you’re going for.

Step 4: Blend the Dry and Compressed Signal to Taste.

Once your settings have been made, begin to blend the compressed and dry signals together to get the perfect sound. I recommend you bring the fader of the compressed track all the way down and slowly bring it up until you find a blend you like.

You’ll find that a little bit of volume can go a long way, so don’t be alarmed if you don’t have to bring your fader up very high for your parallel compression to become effective.

Additional Tips and Tricks for Parallel Compression

Once you’ve got the basics of parallel compression down, here are some additional tips and tricks for your setup. These can enhance the sound of your parallel compression and make it very effective in your mix.

1. Only Send Drum “Shells” to Your Compressor

When using parallel compression on drums, I’ve found it sounds best if you only send the drum shells (a.k.a. the kick, snare, and toms) into the compressor. Sending the cymbal, overhead, or room mics into it often results in a very harsh sound that makes your drums less punchy and muddier.

2. Add EQ to your Parallel Compression

Sometimes placing just the compressor on your desired track will not create the desired sound. This means you might want to experiment with other compressors to get a different sound. Other times, you just might not be happy with, for example, how the low end of a track sounds through your parallel compressor. In this case, a simple move like adding EQ can eliminate this issue.

You can place the EQ before or after the compressor, depending on your needs. EQ is typically placed before a compressor to make any frequency adjustments to the dry audio before it hits the compressor. The goal is to improve the compressor’s response to the audio. EQ is placed after a compressor to make any frequency adjustments to the compressed audio. This improves the tone of the compressed audio without affecting the character of the compression.

(Check out this article if you want a more in-depth discussion on where EQ should go when dealing with compression.)

3. Get Rid of Breaths In Your Vocals

When using parallel compression on vocals, it is important to get rid of any breaths. If these are sent to your parallel compressor, they will become very obvious and distracting in your mix. There are a couple of ways to do this. I prefer to just go through the vocal track and cut out any breaths, applying fade-ins and fade-outs to the beginning and end of clips.

Another option would be to apply a gate to your vocals. You can set the gate’s threshold so that it is only triggered when the vocalist starts to sing.

4. De-Ess Your Vocals

Parallel compression on vocals may increase the amount of high-frequency content in them. This is the range where sibilance (loud “sss” sounds) can occur, and it may make your vocals sound harsh. Applying a de-esser after the parallel compressor can help to tame the sibilance added by the compression. You can make the settings pretty aggressive because the compression is just as aggressive – they will balance each other out.

Applying a de-esser can work for instruments other than vocals as well. A de-esser is essentially a high-frequency compressor, so experiment with using it to tame excessive high-end when using parallel compression on other instruments.

5. Experiment with Tape Saturation

Tape saturation can be a great addition to your parallel compression. Tape saturation is a gentle form of distortion that is caused by pushing the level of an analog tape machine higher than normal. Now there are many plug-ins that recreate this effect.

The extra harmonics created by tape saturation can add a warmer sound to your parallel compression. Experiment with adding it after the compressor, or even creating a separate aux track for it.

If you don’t have a tape saturation plug-in, the Softube Saturation Knob is a great free plug-in to download if you want to experiment with this technique. The plug-in I use for this is the Waves J-37, which emulates the tape machine used in Abbey Road Studios!

Adding Tape Saturation with the Waves J-37.

For an in-depth discussion on tape saturation and tape saturation plug-ins, check out this article.

6. Experiment with Using Multiple Parallel Compressors

Sometimes you can’t get the right tone for parallel compression with one compressor. In this case, you should experiment with creating multiple parallel compression tracks and blending them together. Mixing the sonic qualities of different compressors together may give you the unique sound you’re looking for.

Using multiple parallel compressors can help you craft a unique sound.

Final Thoughts

Parallel compression is a great technique to use if you want to add punch to a track while retaining its natural dynamic quality. This simple technique can take your mixes to the next level. As we can see, there are a lot of creative things you do with parallel compression in order to put your own unique spin on it. Take some time to experiment with this technique in your next mix!

(We’ve rounded up the best free compressor VSTs you can find on the net! Make sure you check out VST Shootout: 6 Best Free Compressor Plugins.)