Compression: broadband, multiband and spectral

August 10, 2022 | Know-how

To balance dynamic fluctuation or give a track more character, a compressor is just the tool for the job. However, there are different types – aside from a lot of tonal-specific types: Broadband, multiband and spectral compressors. We show you, for which use cases each compressor type works well and how smart:comp 2 has got you covered when working on the dynamics of your track.

Behind almost every well-polished track, there is a compressor. The dynamics of nearly all professionally produced songs are shaped in some way – in single tracks or even the entire mix. Compression can be used in many ways which makes the topic itself quite complex. There is no reason to be put off by this complexity though. It’s actually worth it to dive into the topic because compressor, although often subtle in their effect, can work wonders.

We suggest using high quality headphones or studio monitors when listening to the following audio examples.

Broadband compression – the classic

Most compressors, be it hard- or software, are broadband compressors. They analyze and work on the dynamics of an input signal across the entire frequency range. When a set threshold is exceeded, the entire signal is affected, regardless of which frequencies the energy (resp. the level) of the signal is composed of.

Graphic example of analyzing an input signal in a broadband compressor

The level of louder parts is reduced while more quiet areas remain the same. This level-dependent compression lets you limit the dynamic range in order to achieve a more consistent sound. Broadband compression works great to give single instruments a more balanced sound or to merge melodic groups into a tonal entity.

The vibe of following example, an electronic guitar, is okay but there are severe differences in the level of the loop, making it hard to place it in a mix properly. By using a broadband compressor, the dynamic range of the signal is compressor. This makes the guitar sound much more consistent in the mix.

E-guitar track without broadband compression:

sonible · sonible_eguit-no-broadband-compression

E-guitar track with broadband compression:

sonible · sonible_eguit-with-broadband-compression

Broadband compression can be problematic though, when an element of the track affects the compression in a way that impairs the overall sound of the entire track. Take for example, the kick of a drum break that’s very loud and has strong transients. Due to the threshold being exceeded quite quickly, the entire level is being decreased. Even elements of the frequency spectrum are compressed, like the hi-hats, that would’ve needed no work at all. The results are: A kick that doesn’t come through properly anymore, the drum break itself lost punch, the transparency suffered and the entire sound becomes dull.

Drum break without broadband compression

sonible · sonible_drumbreak-no-broadband-compression

Drum break with broadband compression – not always the right choice.

sonible · sonible_drumbreak-with-broadband-compression

Sure, you could counteract by setting a longer attack time. This does help to preserve the transients better but it does not solve the problem of a badly balanced kick in the drum break. What really solves the issue is a multiband compressor.

Multiband compression – more options

In a multiband compressor, the entire frequency spectrum is split up into multiple bands that can be parametrized independently from each other. Hence, you are able to compress a single track or instrumental group much more flexible and heavier, without having to fear that bigger changes end up being audible too much.

Graphic example of a multiband compression and gain reduction for each band

Let’s take the example of the above mentioned drum break with a loud kick: With a multiband compressor, you can place a band right in the area, where most of the kick’s energy is. When setting a heavier compression for this specific band, the kick is tamed without affecting the other elements of the drum break. This maintains the clarity and transparency of the other signal parts.

A multiband compressor also works well, when you want to compress the frequency areas of a dense instrumental individually. In the following example, mainly all the noises should be controlled that occur from the strumming of the guitar strings. Since they are in the higher mids, you can place a band there – without make up gain – and reduce the noisy parts with suitable compressor settings.

Guitar without multiband compression:

sonible · sonible_guit-no-multiband-compression

Guitar with multiband compression:

sonible · sonible_guit-with-multiband-compression
INFO The way a multiband compressor works is very similar to a dynamic EQ in some aspects. However, they differ from each other regarding their typical use cases. Thanks to the possibility to make filter bands very narrow, dynamic EQs are used to remove disturbing frequencies in a highly precise manner. A multiband compressor, with its bands covering the entire frequency range, work better to give complex signals a homogeneous sound.

The disadvantage of multiband compressors often lies in the complexity of parametrization, since the transition-frequencies as well as the compressor parameters for each band have to be set. Each mistake can lead to a frail and inconsistent sound because the spectral homogeneity isn’t given anymore.

Spectral compression – a new way,  a new solution

What to do, when broadband compression doesn’t work for the desired tonal goal and the limits respectively complexity of a multiband compressor hinders the workflow?

This questions already occupied our minds intensely in 2017, when we worked on the first prototype of smart:comp. Our demands were high: high-resolution multiband compression that adjust itself automatically to the dynamic and spectral characteristics of the input signal but can be handled as easy as using a broadband compressor.

The result of this ambitious vision is the development of our new concept “spectral compression”. While usual multi band compression is limited to 3 or 5  bands, spectral compression works with up to 2000 bands that continuously correct dynamic and tonal imbalances. Compression is automatically only applied, where it is necessary. This approach results in a very transparent and clean sound. 

How does spectral compression work?

This highly targeted compression is only possible because spectral compression does not only compare fixed thresholds and signal levels with each other. The spectral distribution of energy of a signal is analyzed continuously and compared with target values that have been calculated by intelligent algorithms. When the system recognizes that certain frequency areas are currently being overemphasized and therefore affect the compression disproportionately, these areas are automatically compressed more. The intelligent, frequency-dependent compression takes care that even bigger changes are hardly audible and the transparency of the signal is maintained – or even maintained.

Example of how spectral compression works with the help of profiles

With the help of profiles, the spectral compression can be aligned to different input signals to optimize them even further.

Similar to multiband compressors, the frequency range that should be affected by spectral compression can be limited. Restricting the processing to a certain area is great, when you want to keep the remaining areas overemphasized due to aesthetic reasons.

Spectral compression works for any kind of signal  – especially single tracks and mixes with overemphasized frequency areas.

The following drum break should be compressed heavily but without the consequences of a changed sound. Spectral compression mainly is applied where the kick has got a lot of energy and solely there where compression is necessary. This way the drum break sounds very transparent and clean after compression.

Drum break without spectral compression:

sonible · sonible_instrumental-no-spectral-compression

Drum break with spectral compression:

sonible · sonible_instrumental-spectral-compression