“I don’t want to hear things flying around my head” is a comment I’ve heard frequently from people who are unconvinced about immersive music mixes. I’d have to agree that in the majority of cases conspicuous panning moves are attention grabbing first time, but over time become distracting, just like they do in stereo mixes. However to equate immersive mixes to dynamic panning would be to mischaracterise them. In this article I’m going to outline a few ways in which immersive mixing makes some of the techniques which many mixers employ to create space for all the elements in a busy stereo mix unnecessary, and why they will still be around for years in spite of this.
For years we’ve been trying to fit more and more information into a stereo mix. Stereo has always been limited to the 60 degrees between the speakers (at best) but for many years we were artificially restricted by a self-imposed (and most would say self-defeating) requirement for hugely loud mixes with a corresponding lack of dynamic range. Trying to fit sometimes hundreds of tracks into a narrow ‘letterbox’ of stereo panorama and dynamic range has given rise to some ingenious tricks to create space where there was none. In some genres much of the skill for a mix engineer is to make a mix which fits these requirements and still sounds satisfying in spite of it.
What kind of techniques am I talking about? Here are some examples:
EQ Carving
Sonnox Claro - Sidebar indicating potential clashes
This has always been a source of controversy. Many people believe that issues with creating space in a busy mix for all the elements to coexist and remain audible are best dealt with in the arrangement, and that’s hard to argue with. But it is undeniable that in recent years the concept of identifying areas in the mix where two instruments are in danger of overcrowding an area of the frequency spectrum and addressing that by ‘carving’ or reducing the energy in a particular part of the spectrum on competing parts to create space for another element is seen as de rigeur. Some more sophisticated EQ plugins such as FabFilter’s Pro-Q 3 or Sonnox’s Claro even provide tools to help identify potential clashes. The risks of auditory masking are real and if sounds compete then, rather than making them harder to distinguish, masking can obscure them completely. If competing sounds are moved away from each other in the stereo field then this potential masking can be solved to some extent but, as there is so little room in which to place sounds in a stereo panorama, EQ carving is a common solution.
Side Chaining
External side chaining is a common technique for managing headroom in a mix. If, for example, the kick and the bass when summed together exceed full scale something has to give. If you don’t want to compromise the sound of either element then side chaining the less important sound by keying a compressor to attenuate it when the more important sound is playing is an excellent way to fit both sounds into the available headroom. The fact that, when pushed far enough to sound obvious, it gives an impression of power is also a useful byproduct.
But side chaining is also a useful way to manage ‘perceptual headroom’. Mix elements might not be pushing the headroom below digital full scale too far but if a sound is more than 3dB quieter than a competing sound then it is at risk of being masked. Using external keying to reduce the level of the competing sound, either using a full bandwidth compressor or ducker to attenuate the signal, or using a dynamic EQ or multiband compressor to dip just part of the spectrum, is an effective way to buy a little more room in a busy mix.
Stereo Widening
Stereo conveyed over loudspeakers has an apparent width of about 60 degrees, but that is a best case scenario and we all know that most people listening over loudspeakers are probably hearing a less than ideal stereo presentation. And while people listening on headphones will definitely hear both channels, there are other issues with headphones.
Stereo has a fixed width, though widening techniques exist.
There are several techniques available which can extend the apparent width of stereo material. Along with ‘louder’ and ‘brighter’, ‘wider’ is one of the more addictive qualities requested in mixes and many ways of achieving this are available. But all come with downsides, particularly when mono compatibility has to be maintained, an issue which continues long after compatibility mono broadcasts have become less important. As we highlighted in our article If You Don't Want Your Mixes To Sound Bad On The Latest Audio Equipment Then Start Doing This Simple Test Now! some smart speakers are mono and many others have a single mono bass/mid driver and stereo HF drivers, in either case mono compatibility is important when mixes reach the consumer.
But when an immersive mix has a full hemisphere of soundfield to occupy, the role of artificial widening changes significantly. Mono or stereo sounds can be placed anywhere. However concerns about upmixing become more significant, as do matters of downmixing, but with the increase in channels the tools available to upmix, and the care with which they are implemented has gone up significantly and tools such as those from Nugen and Penteo are significantly more precise than using MS processing or Haas delays.
What Does This Mean For Music Mixing?
One of the biggest adjustments mix engineers have to make in this new world of immersive mixing is to adapt to the relative lack of restrictions compared to stereo mixing.
As already stated there is a vastly enlarged panorama in which to place sounds. The temptation might be there to place elements of music mixes all over the soundfield and this can be very effective, but usually a conventional forward facing mix, which probably isn’t all that different in intention to a stereo mix, is more appropriate. But the fact that sounds are no longer as tightly constrained in their placement means that the need for carving and side chaining, and all the other techniques to fit more and more into a small soundstage, fall away.
I should also mention the increased dynamic range available. Spotify, YouTube, Tidal and Amazon Music all normalise to a loudness of -14LUFS, Apple Music is more generous at -16LUFS, Dolby Atmos For Music has a target loudness of -18LUFS. More dynamic range gives greater freedom but as our recent experience with loudness normalisation of stereo material, many engineers are reluctant to use all of the available dynamic range, feeling that the use of limiters, which was necessary to ‘compete’ during the pre-loudness normalised days of the Loudness Wars, is still necessary as an aesthetic choice to keep the music sounding appropriate for the genre. The sound of limiting in itself is felt by many to be desirable.
In the same way I’d expect that many of the mix techniques which were used to solve the technical issue of fitting all the elements of a complex mix into a stereo format with restricted dynamic range will continue to be used as a creative choice to keep the music sounding ‘correct’ for the genre and to exploit some of the aesthetic qualities these clever techniques bring with them.
And while immersive formats bring many benefits, and solve some intractable limitations of stereo, they do introduce issues of their own. One of the most pressing is the need for an effective way to replicate the bus processing, particularly the use of bus compression which creates the dynamic interdependence between elements of a mix which confers that cohesive quality or ‘glue’ which we associate with the sound of records. These are technical issues which are being solved and already some partial solutions exist like PSP’s auralComp but there is more work to be done, for example Fielder Audio’s Mastering Console features a compressor which can process the beds and objects in an ADM, something a channel based compressor cannot do. What this does illustrate is that new solutions inevitably bring new problems.
What do you think? To what extent will these techniques which have become associated with the sound of stereo persist into the immersive formats of the present day? Share your thoughts in the comments.