This is such a common question among producers. The answers, however, vary depending on who you ask. It really depends on how much a producer understands the technical aspects of mixing and mastering.
If you want to know how much headroom for mastering is standard practice, the simple answer is that there is no standard. Nonetheless, certain guidelines exist to make life easier for you and your mastering engineer. If you want to know how much headroom you should allocate for your particular mix, it would be better for you to grasp the fundamental concepts first and then adapt them to your personal practice.
What is Audio Mastering
So what is audio mastering and what it is for?
You may have already encountered the word “master” a couple of times in your DAW. The final channel in most mixing controls is usually called the ‘master track.’ Basically, it’s called a master track because the mix that comes out of it is the actual sound or ‘master’ version of your mix.
However, when distributing a mix or preparing a collection of multiple tracks (an album or an LP, for example), most take an extra step called ‘mastering.’
Usually done by a mastering engineer, mastering refers to the process of adding some finishing touches to a track or a collection of tracks.
This usually includes unifying a sound or making the tracks sound like parts of a whole, keeping levels and audio characters consistent throughout an album, and preparing the track for release depending on the medium of publishing.
For example, a track released for streaming will be mastered differently when it is released on vinyl or tape.
A mastering engineer should also make more mix as loud as permissible in a given medium. You don’t want your track to sound weak and unremarkable when listened to side by side with another track. It is the mastering engineer’s task to furnish your track and give it some presence in the wild.
Headroom needed for mastering, and why
Before we delve into the details, let’s first define what exactly is headroom, and why is it important.
When producing and mixing, we are working inside a defined territory of frequencies. At the lowest end of this territory is the noise floor. This refers to the minimum loudness your mix can get until all you hear is a steady hiss or noise.
On the other hand of the spectrum is the clipping point which refers to the point where your system can no longer properly process your signal. If a sound goes beyond the clipping it, it gets distorted and generally sounds bad.
One of your tasks as a mix engineer is to prevent your mix from clipping. Of course, it should also be loud enough so you can hear all the details in the mix.
As we have already mentioned, one of the tasks of the mastering engineer is to make your sound as loud as possible while complying to certain industry and medium standards. Obviously, the mastering engineer cannot do a lot of things with a mix if it is already loud. This wiggle room where the mastering engineering can do his or her magic is the headroom.
Think of the headroom as a buffer zone, an area that can accommodate unexpected loudness and transients and avoid clipping. A large headroom gives the mastering engineer a lot of area to work on. He/she can highlight some frequencies, automate levels across the mix, basically anything to make your mix sparkle.
So much headroom do you actually need?
There is a so-called rule the -6db Rule which dictates that a mix should never go beyond -6db.
However, this rule is more of a guideline than an industry standard. Some producers set -3db as the threshold for their mix. Some adventurous ones set it at 0db, which is the absolute limit since anything beyond that could result in clipping.
Therefore, technically speaking, you can have as much or as little headroom as you want as long as you don’t clip. This is the case with fixed-point mixes (16 or 24-bit) WAV.
However, if you are exporting to 32-bit floating-point WAV, you can even go beyond 0db or full-scale, because this format allows the mastering engineer to turn down the levels of your mix.
Ok, so you’re not one to live on the edge and you would rather give your mastering engineer as much headroom as possible. In this case, you also have to take care not to mix too low and near the noise floor.
Why? Some master fader plugins add some almost-imperceptible hiss or color to your mix, and mixing too low can contaminate your mix with these elements. Color and ‘warmth’ should be subtle and definitely not be in the front and center of your mix.
You also have to take care when using analog equipment or using analog to digital converters. Analog equipment usually adds some color and warmth to the mix. This cannot be seen in your DAW. Therefore, consider this when mixing down as these hiss and color take up some headroom.
Take a look at our article about gain staging in the signal chain, as this will help a lot with determining the correct amount of headroom for you.
You should also avoid using peak limiters when dealing with loud audio. Peak limiters will create more headroom, but they also cut away and distort important frequencies that go beyond the set threshold. Instead of using a peak limiter, simply do some gain staging and manually adjust your tracks’ levels.
As you can see, there is no definite answer to the question of how much headroom for mastering is needed. Just strive for that sweet spot where you can still perfectly hear all the elements in your mix without going beyond 0db. If you want to set a fixed threshold such as -3db or -6db, then, by all means, go ahead. What really matters is that you give some headroom while also making sure that you can work comfortably at a given level.