If you’re reading this, you’ve probably had some experience with parallel compression, the process of blending a compressed track or submix with an uncompressed copy. Getting this balance right allows us to enhance the punch and power of a signal without altering the original transients or eating up lots of mix headroom.
But in pursuit parallel compression perfection, there are common obstacles that might prevent you from getting the sound you want. I’ve listed six here along with tips to sidestep them.
As with all mixing scenarios, it’s a lot easier to evaluate your decisions if you know what you want to accomplish in the first place. Compression on its own is a confusing topic, especially for newcomers, and going parallel just for the sake of it can complicate things even further since we’re now using the processor in an excessive way.
I typically employ parallel compression when working with signals that have clear transients, but quiet, low-level information that seems to get lost among other instruments. If I use compression “normally” as an insert effect, I’ll be able to make the soft hits more noticeable, but end up having to reduce transient peaks to do so.
By duplicating the original signal, heavily compressing the copy, then blending both together, I get to retain the original dynamics, while adding the necessary attitude that makes the whole thing seem more up-front. Since the compressed track is mixed at a lower level, I don’t overwhelm the mix with gain either. In this way, parallel compression allows me to apply extreme compression without any of the typical drawbacks.
In a parallel setup, the compression is much heavier than what you would normally use as an insert effect on a track. If we take the scenario described above, I need to dial in anywhere from 10–20 dB of gain reduction to get the sound I want.
For this in-your-face bite, I’ll start with a fairly conservative ratio (with this high level of gain reduction even low ratios sound dramatic) and pull the attack time toward the faster end of the dial, landing somewhere between 0–5 ms. Since the original signal already contains most of the impact I want, this attack setting tells the compressor to clamp down near-immediately to squash transients, avoiding an overly punchy mix. Additionally, if you’re working with short samples, a long attack won’t grab the signal in time.
Depending on how much of the quieter information you want to be pulled up, a short to medium release will do the trick. You may even want to bump the ratio up higher to bring out some exaggerated pumping and intentional distortion—in the case of parallel compression, this isn’t always a bad thing!
Like a usual compressor, attack and release controls are set to suit the material and will change from project to project. You might want more transient energy from the compressed signal, and in this case, it makes more sense to dial in a longer attack time and shorter release time.
Once you set up parallel processing in your DAW, you will find the process of setting the right parameters quite intuitive, as the compressed copy is simply there to round out the uncompressed version, instead of shine as a standalone element.
To get additional control over your processed signal, there’s nothing stopping you from EQing parallel compression returns. If you want really beefy low-end, say in a drum kit, try a boost around 100 Hz to exaggerate the attack of the kick or snare. Placed before the compressor, this will drive it to clamp down harder and alter the overall tone, which can be a desired effect. Cutting or boosting with EQ after the compressor allows you to sculpt the signal further to better fit the mix.
Similarly, if you have a compressor that allows for multiband compression, like Neutron, you can split up your doubled signal into custom frequency ranges and assign different compression settings to each. You might want to bring up the lows, but have the compressor work harder on some mid and high range resonance to prevent disrupting the mix balance when blended in.
Parallel compression increases the level of your mix—you are adding another track of audio to your mix, after all. Since we have a preference for louder over quieter, it's hard to know whether the decisions made in parallel are improving your mix or just playing to our natural bias.
To get a better read on this, I fade my compressed track into the mix until the original signal starts to feel rounder and more powerful without getting much louder. If you take away the compressed signal it should feel like your mix is missing something, but not necessarily sound quieter.
As a new mixer, you may benefit from a meter, like Insight 2, that provides visual feedback on the levels and loudness of your mix before and after parallel compression. While bringing in the compressed signal, monitor the readout displays to gauge how much of an increase it brings. If the dials heat up and this isn’t your original intention, you may want to bring the compressed signal back down and re-evaluate your approach.
In a parallel setup it might be appropriate to send your entire signal to a compressor return, but this isn’t always the case!
If you only want to beef up the kick and snare, send only those sounds and leave the rest untouched. When mixing live drum kits, room mics and other ambient material will start to splatter when you heavily compress them in parallel, especially if some compression was already applied to the “dry” signal for consistency. Again, this isn’t a set rule, and there may be certain sections in your song where bringing up the room in this way will give you a more lively sound.
Use a similar thought process when sending a signal with time-based effects to a compressor return track. A big reverb or delay will surely change the way your compressor acts and may lead it trigger when you don’t want it to.
The stealthy quality of parallel compression can lead us to believe it’s the secret sauce that will take our mixes to the next level. As a result, we start to overuse it and apply it in big slabs all over the place.
I have found some more interesting results (and had more fun getting there) by dialing up parallel compression in smaller amounts at various stages in a signal path. You may want to use one compressor at the instrument level for distortion and another for warmth, then add a third on the related submix for level, or even on the master output.
So, give this a try in your own mixes. Do your drums, vocals, and whatever else sound best when you apply parallel compression in one go? Or does a more splintered approach give you the desired sound?
There are many benefits to using parallel compression, but like all techniques, there are also pitfalls. The tips in this article should give you a clear idea of when you’ve fallen into one of these traps and how to get out.
To leave you with one final piece of advice—learn how to use compression with (moderate) confidence before diving into the world of parallel processing. Without this knowledge, you may end up using parallel setups simply because they offer a greater safeguard than insert effects against compression mistakes. Improper settings won’t do that much damage when buried deep in the mix, but they will in just about every other scenario.
To learn more about compression, follow our Pro Audio Essentials video course.