In this tutorial we will be using parallel processing to add more power to the drum track below.
To understand what parallel compression is and why we may choose it over standard compression, we must first take a look at the fundamentals of how compression works.
There are a number of complications that can make compression a difficult subject to understand, such as:
Compressor Types: FET, VCA, VARI – MU, OPTICAL
Compressor modes: Downward, Upward, Expansion, Parallel
Compressor settings & Algorithms: Peak, RMS, Attack, Release, Ratio
Compressor tasks: Peak reduction, Glue, Colouration, Adding weight etc.
COMPRESSION REDUCES DYNAMIC RANGE
In the case of most compressors, this is done using downward compression. This involves squashing the loudest parts of the audio down. The output level is then increased via the makeup gain, so that we perceive the overall volume as being louder.
This works well for most situations. But because we are squashing a signal down we will be drastically affecting the dynamics of our loudest transients. This is because we are squashing them down at the mercy of the compressors attack and release settings, which will change their shape and tone considerably. Inexperienced producers often make the mistake of completely flattening the dynamics out of their signal in an effort to get the extra loudness and weight they desire.
There are many cases when we will want to increase the overall loudness of a part or track, without affecting our precious transient peaks.
Ideally we want to use some form of upward compression rather than downward compression. Meaning we want to make the quieter parts louder (without affecting the peaks). This in itself will also cause its own set of issues, such as raising the level of the noise floor. So instead of using a form of upward compression we use parallel compression.
WHAT IS IT?
Parallel compression became popular in New York, so it is often referred to as NY or New York compression. It’s actually just bog-standard downward compression. The only difference is that it is ran in a parallel configuration with the original uncompressed signal.
The results are similar to that of upward compression, but without the issue of raising the level of the noise floor to unsatisfactory levels.
So just to re-iterate:
downward compression reduces a signal above a set threshold (squashes loud parts down)
upward compression raises the signal below a set threshold (squashes the quieter parts up.)
Each one of these methods has problems. And parallel compression is the answer to get the best results with minimal side effects. Parallel compression will reduce the dynamic range without reducing the peak level or drastically affecting the transients shape. It will do this by raising the level of quieter signal components by summing the signals together.
This technique involves applying harsh compression settings to a copied version, which is then blended back in with the original audio.
This can be done in a number of ways:
· Setting the dry/wet to 50%
· Using a return track
· Duplicating the track that we wish to compress and processing separately
We recommend the technique of duplicating the track we wish to compress, as this will give us more control over how we choose to blend this compressed signal back into the original.
WHY USE PARALLEL COMPRESSION?
Compression always comes at a price, the tradeoff between a loud signal and a dynamic one. Parallel compression allows us to have both to a greater extent.
We will use the example of a drum group:
If we think back to phase relationships, we know that adding two similar waveforms together, in phase, will add significant volume to the sound.
By heavily compressing a copied version of our drum group, we will be flattening the dynamic range and taking all of the transient punch out of the signal, but we will also have a much higher average RMS volume.
We can now mix this signal back into our original signal. As we blend this back in, the quieter more detailed parts of the original audio will fuse together with the duplicated signal, giving us a much more powerful sound, whilst leaving our original peaks untouched.
By doing this we are getting the best of both worlds, a combined mix with lots of dynamic transient information as well as a powerful compressed sound. We can also use our compressors to add pleasant warmth and distortion, or better yet we can set up another parallel chain and heavily saturate the signal, then blend that in with both the compressed signal and the original audio.
We can now blend the squashed signal in to the original dry signal either by using the wet/dry knob of a compressor, the send/return, or by bringing the parallel channel fader up. The resulting signal will now benefit from both the louder RMS volume and the strong dynamics.
parallel compression settings vary from moderate compression to complete limiting.
The aim is to see a large amount of gain reduction on the loudest parts of our track. For this reason, the threshold setting is vital and will usually result in around 20dBs or more of gain reduction.
one of the reasons why the threshold setting is so important is because this is going to be the point at at which the dynamic range is retained above the signal. (The peaks above this threshold in the final sound will be much more preserved than in standard downward compression)
setting the threshold too low can cause the side effect of raising the noise floor, whereas setting the threshold too high will result in losing too much dynamics in the combined signal. The threshold setting is the single most important setting for parallel compression which will require fine tuning on a track by track basis.
The signal below this set threshold will be left completely uncompressed (no gain reduction). This will mean that when this signal is blended with the original signal, it will sum together causing an increase of 6dBs. This means that we will have made out quieter parts louder (increasing the average level, without affecting our loudest parts)
We have found that it is best to turn the makeup gain off, this allows us to set the output gain appropriately so that we can bring the quietest parts up to a satisfactory level manually. Alternatively we could use the parallel channel fader to achieve the same result.
We suggest starting with a fast attack time and a fast release time. This will give us an energetic sound, Why not make the attack slower we hear you say? This is because we already have strong transient information in the original audio, if we make the attack slower, the transient will be allowed through the compressor, which means we will get an increase in volume of the transient at the output.
Keeping a fast response time is fairly typical for parallel compression, however we can back the attack and release times off a bit to keep things a bit more natural or to allow more transient through if necessary.
Parallel compression ratios vary widely on the signal in question. Anything goes, but generally we can expect fairly radical compression values between 4:1 and limiting.
A ratio of 10:1 or more with a large amount of gain reduction will most likely make the signal sound absolutely unusable and horrendous on its own. This is fine because the parallel chain will only ever be heard in conjunction with the original signal.
ADVANCED PARALLEL PROCESSING
Parallel processing can be used multiple times on a single track. Using multiple parallel chains with different compressors can help to add different sonic characteristics to a part without ruining the transients. This can also be done using a compressor combined with a saturation or mild distortion plugin.
These saturated parallel tracks will also sound like they would never work in the mix when monitored in solo, but when mixed in at low volumes they add a good contribution to the overall sound and harmonics of the signal.
A further step that can improve parallel processing is to use an EQ plugin in the parallel chain to define the exact area to be parallel processed. This can stop a boomy low-end from getting out of hand, and can really help to bolster the power in the mid and high frequencies to give a mix the energy it requires. Be aware when EQing parallel chains that strong filter slopes can alter the phase relationship and cause phase issues, so use a linear phase EQ or shelving filters and gentle slopes.
Parallel compression works very well for adding power to the drums, and bass-line depending on the type of sound and programming used.
This is also the perfect tool for giving vocals more attitude and presence whilst maintaining their dynamics.
Try to choose the tracks to parallel process wisely. Parallel processing every track in the mix will not make the whole track better, its all about deciding what elements need this kind of treatment and giving the mix a nice contrast.
This is an excerpt from book 3 of our Zero To Hero Mix Series covering Compression & Dynamics.