Learn how to achieve more professional mixes with these four bus-processing techniques
If you’ve spent any time researching how to achieve more professional mixes, you’ve probably come across the term bus processing. Even if you’ve not heard of the technique, you’ve likely employed bus processing in a mix at some point or another.
Whether you’re an audio engineering novice or an intermediate user looking to level up your mixing know-how, this article will teach you four bus-processing techniques for delivering better mixes. While we’ve suggested some approximate processing settings for some of these techniques, it’s important to use your ears and make mixing decisions based on the source material and your desired sound.
In the world of audio mixing, bus processing refers to the practice of applying the same processing to multiple channels. This is achieved by sending several channels to a single channel, also known as a bus, and then applying processing to that bus.
For example, a drum bus contains multiple drum channels, an effects bus contains a number of effects channels, and a mix bus contains all channels and buses within a mix project. Bus processing brings several advantages and new creative opportunities to the mixing process, some of which we’ll discuss below.
One of the most popular uses of bus compression is a technique known as glue compression, whereby multiple elements are compressed together in order to ‘glue’ them into one cohesive audio signal. This is particularly useful on highly dynamic elements, such as drums and percussion.
While there are a whole host of compressors on the market that promise to be the final word in glue compression, the truth is that with the right knowledge, you can apply glue compression with just about any compression plugin.
In this example, we’ll be using DynOne to add cohesion to our drum group. For traditional glue compression, we want to apply the processing as an insert rather than in parallel, so we’ve added our compressor directly to the drum bus.
DynOne is a powerful multiband compressor with up to five bands of compression. In this case, we only need a single band as glue compression is generally applied to the full frequency range, as we want to ‘glue’ the entire signal together. For this reason, we want to switch off four of the five bands using the corresponding On/Off buttons. We also want to switch off DynOne’s Parallel Mode for now, but more on that in the next section.
With Parallel Mode off, we can now increase the fader, which controls the level of the compressed signal. With the fader at 0dB, we are essentially hearing the compressed signal at 100% wet, and we can begin dialing in our compression settings.
Glue compression is a relatively subtle form of bus processing, so we want a relatively low ratio of around 3:1. For the same reason, we want a slow attack time. This means that the compressor allows the transient information of our drums through before it begins to control their dynamics. A fast release time helps to preserve the transparency of our signal and lets the compressor recover before the next drum hit.
With our compression ratio and timing settings configured, we can start to adjust DynOne’s Threshold until we reach the desired amount of gain reduction. Again, this is a subtle technique, so we’ll only apply up to 3dB of gain reduction at the loudest peaks.
We can then fine-tune the Ratio, Attack, and Release settings to refine the compression being applied. If the sound is too snappy, try reducing the Attack time. For more natural-sounding compression, try reducing the Ratio or increasing the Release time. You can utilize the A/B functionality found in all Leapwing Audio plugins to ensure you’re making effective mix decisions.
The previous technique used bus processing to achieve a fully compressed signal, but bus processing can also be used in parallel to achieve a fuller mix. Like the glue compression technique, parallel bus compression also helps to create a more cohesive mix.
This is made particularly simple with DynOne’s integrated Parallel Mode. Unlike most compressor plugins that have a traditional Dry/Wet control, DynOne lets you mix the actual level of the compressed signal in with the dry uncompressed signal. This makes DynOne particularly useful for giving instrument and vocal buses more body, without sacrificing clarity and detail.
Start by placing DynOne on a vocal or instrument bus. By default, DynOne is in Parallel Mode, meaning the plugin outputs only the unprocessed signal with the faders at -∞. For now, let’s switch Parallel Mode off and raise the faders to 0dB. This way, the plugin outputs only the processed signal and we can set the compression more accurately.
Because we will be mixing the dry signal back in with the processed signal, we can afford to be more heavy-handed with the compression we apply. Try a Ratio of around 10:1, and set the Attack and Release times according to the qualities of the audio you want to accentuate. For example, faster attack times and slower release times will tame the transients and bring out the body of our vocal bus. The inverse will emphasize the transient portion of our vocals and attenuate the body.
Reduce the Threshold until you achieve 6-12dB of gain reduction. With Parallel Mode off, this may sound overcompressed and unnatural, but once we engage Parallel Mode to reintroduce the dry signal, the original clarity of the vocal will return.
Bring the fader back down to -∞, reengage Parallel Mode, and then raise the fader to mix the compressed signal back into the dry signal. This leaves you with a fuller vocal bus that can take the stage at the forefront of your mix.
Don’t forget to use DynOne’s Output Gain fader to compensate for any level being added by the processing. The K-Weighted LUFS loudness meters on the plugin’s input and output allow you to set your levels with complete confidence and accuracy.
This bus processing technique will not only help you to improve the sonic quality of your mixes, but it will refine your mixing workflow too. One of the advantages of bus processing is that it enables you to simultaneously adjust the processing being applied to an entire group of instruments, or even your master bus.
You’re probably familiar with the term dynamics; the difference between the quietest and loudest parts of a signal, but what about macro dynamics? This refers to the difference between the quietest and loudest sections of a song. Considering your mix’s macro dynamics can help you create a more impactful and exciting mix.
Try combining this concept with one of the bus processing techniques explained earlier in this article. For example, you could introduce parallel bus compression during the choruses to create a greater impact during those sections. This technique isn’t limited to dynamics-based bus processing; you could apply a subtle room reverb to your vocal bus during the verses to set the vocals further back in the mix.
One of the biggest questions around the topic of bus processing is ‘Should I mix into a compressor or limiter?’. Like many questions in music production and sound engineering, there is no definitive answer. What’s important is understanding the advantages and implications of the techniques you’re using, and doing whatever gets you the best-sounding results.
The big argument for mixing into a bus processor is that it can help to give you an idea of what your finished mix will sound like, thus helping you to make appropriate decisions throughout the process of your mix. It can also help you to identify issues within your mix earlier on, allowing you to address them immediately.
Start by placing a limiter at the end of your mix or master bus. Due to its transparent sound and intuitive controls, we’re using LimitOne, our spectral limiter and clipper. We’ve reduced the Ceiling to -0.3dBFS, meaning the limiter will prevent our mix from exceeding that level.
Now raise the Drive level until the limiter is applying a maximum of around 3dB of gain reduction. While this only applies a relatively subtle level of limiting, it should give you some indication of how your finished mix will sound when mastered. It will also highlight when a particularly loud peak within your mix is likely to cause an issue during the mastering process.
By frequently checking what your limiter is doing, you will be able to quickly identify when you have a deeper issue in your mix. For example, if your snare is triggering your limiter to apply an additional 3dB of gain reduction, you’ll know to go back and reduce the snare’s level, apply individual dynamic processing on that element, or both.
You should now be able to apply these bus processing techniques to your own mixes in order to tackle a range of problems during your next mix. Head to the DynOne and LimitOne product pages for more information on each plugin, and to download your free full-featured one-month trial.
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