Although this article is about mixing for loudness, not mastering for loudness, the two arts are inextricably linked. It's no secret that there's still a loudness war waging, putting pressure on mastering engineers to raise the levels of recordings to the point that audio quality is often compromised in favor of perceived volume.
The practice of competing for loudness at the mastering stage seems especially misguided, since some styles are generally louder than others due to the ways in which they're produced. It's silly to expect an intimate, acoustic guitar-based track to match or exceed the levels of a screaming death metal band. for example. Furthermore. it's logical that such a death metal band might want their song to be recorded violently loud. The values of the track in question should govern those sorts of decisions, which should be made on a case-by-case basis.
Supposing that your values demand a recording that's competitively loud, at least in part, the potential results of a mastering job will depend on how that particular track has been written. arranged, produced and mixed. We'd even contend that the steps before mastering are collectively far more important to the recording's loudness potential than the mastering itself.
Throughout this article, we'll assume that you have a basic understanding of how to use the common production tools - but just in case, we've made every effort to make things easy to follow if you don't. Our goal is to encourage you to consider and learn about everything that contributes to the loudness of a track prior to mastering. Some of what's covered might be considered somewhat unconventional, but that's the nature of the task at hand- essentially, the art of chasing headroom.
Every producer must strive to control the loudness of their mix at some stage. Suppose we were to attempt to divide all producers into two categories. One category is made up of those people who simply want their music to be as loud as possible. The other category is of those who want the option to be able to use contrasting dynamics to their advantage.
For those in the first category, there's immediate value in any technology or technique that helps them to realize a loud sound with little compromise to the integrity of the audio as possible. However, in order for those in the second category to achieve maximum dynamic effect, they must fight the limitations that current technology has with regard to quiet passages, as well as mastering the art of maximizing loudness. If they're able to do this, their ability to operate effectively at both extremes frees them to fully exploit the dynamic range available to them.
Therefore, the better you become at influencing perceived loudness, the better you'll be at keeping clarity and separation in a mix, even when elements of that mix are set at lower volume levels. This is why it should benefit you to learn these skills even if you don't intend to have your music blaring full-blast at all times.
Why so loud?
A loud mix has many potential benefits. We're wired to take notice of loud sounds, no doubt for evolutionary purposes. Primitive humans who weren't alarmed by loud sounds would probably have been at more risk in the event of an approaching predator or natural disaster. Also, due to the non-linear response of our hearing, louder music can potentially have much greater detail in the treble and bass ranges. This helps with the impact as well, because music with a clear top and bottom appears to have presence and impressive perceived size.
An aural illusion it should go without saying that exposure to excessive levels risks permanent damage to hearing. So, perhaps the ability to give the impression of a loud sound at more moderate listening levels is a step towards retaining a degree of that alarming impact without the associated dangers. There are a surprising number of simple methods of producing insanely loud sound - just try stacking distortion plug-ins. The tricky part is doing it in a way that sounds natural, or at least desirable. The unbearable side effects of over-processed audio signals tend to cap the effectiveness of most loudness effects, but used in small doses they each have their place.
It's important to note that perceived loudness is quite a subjective experience - one that's worlds apart from a decibel reading by a piece of audio equipment. As we'll be revealing throughout this tutorial, the loudness we perceive a sound to be at can depend on many small factors, and these are often things that you might have assumed were totally unrelated to each other. This is partly because the brain plays a huge role in the hearing process, leaving us staring down the barrel of that mysterious field of study called psychoacoustics.
Understandably, perceived loudness is something that's incredibly difficult to predict or measure. Happily, though, you can exploit this phenomenon: there are a number of nifty tricks and techniques that can help you work towards attaining the maximum loudness, using as little of the headroom available as possible.
Another way to look at it: when you keep as much spare headroom as you can, you're free to increase actual volume levels later. If you monitor how different elements in a mix work together, you can optimize the overall headroom of your mix, making that aspect of the mastering job a lot easier.
DIY loud patches
If you're daunted by the idea of programming your own synth patches, you'll be surprised at how much you can learn simply by opening up a random preset and resetting the controls one by one. This process requires you to explore the interface and hear what different parameters do, but minus the pressure of having to produce anything exciting. If you have any problems, refer to the manual to quickly find out what anything does or means.
Save this initialized patch to use as a starting point for future patches. It's often much quicker to get to where you want to go from a blank slate, because then you automatically have a better understanding of what each individual setting Is contributing to the resulting sound. Having said that, other people's patches are great for studying if you want to learn new tricks.
For loud patches, try any built-in saturation or distortion that your synth offers. Even the weediest digital waveforms can become dirty hard dance leads or dubstep bass timbres with the right type of distortion.
Take advantage of your synth's key-tracking (if available). This makes parameters respond to what keys are being played and can take your sound places that static Insert effects just can't reach. When cleaning up the bottom end of a sound, it's far crisper to apply a high-pass filter with key-tracking than to search for a static high-pass position on your channel EQ. The latter method will yield inconsistent results across the keyboard.
RMS vs Peak Loudness
As we've mentioned, the human ear only accounts for part of the hearing process. The brain processes all incoming signals in a variety of ways, even adding or removing aspects of the sound, with the result of heavily biasing what we hear. Part of what causes this discrepancy is our perception of loudness over time. Even an extremely loud peak, if quick enough, could potentially go unnoticed in comparison to a much quieter audio event that lasts much longer.
To address this, audio equipment manufacturers invented the RMS method of measuring amplitude. RMS stands for 'root mean square', and it's an equation used to determine the average decibel level of a sound, which is much more akin to how we hear with our ears.
A peak amplitude value doesn't give away much about the overall loudness as we hear it, since that peak moment might occur very rarely - or perhaps only once. This is why you can potentially limit the peak loudness of a sound and thus free up headroom in the mix while barely affecting the overall level (or, more importantly, the perceived loudness) of the signal in question.
In conclusion, then, It's advisable to use RMS metering to get a clear indication of how loud your signal will sound, and also to compare relative levels.
Compression and Limiting
Compressors are generally thought of as tools designed to add loudness to a signal. That's only half the story, though, since their main purpose is to restrict dynamics. The only way to get more volume from a signal using a compressor Is by adjusting its Gain control - but you certainly don't need a compressor for that.
The beauty of using a compressor before turning up the gain is that It can reign in sections of the sound that are unnecessarily loud compared to the rest of the signal. In this respect, compressors are great for squeezing extra headroom out of signals that have a greater dynamic range than required.
This is especially true of limiters, which are like extreme compressors with much higher ratios and usually a quicker response time. Compressors tend to be better at leveling out the overall sound, whereas limiters usually excel at absorbing quick peaks.
Umiters are known to exhibit extremely unpleasant side effects when over-used, but some definitely sound better than others. Software compressors and limiters have come a long way in the last few years and there are some really involved products on the market today, each with its own strengths and particular character. Experiment with a few to find out which you prefer.
Close the gate
Noise gates work by reducing the amplitude of the incoming signal when it falls below a certain threshold. This concept isn't too dissimilar to the workings of a compressor, which reduces the amplitude when the signal goes above a specified threshold. Essentially, gating is really good for suppressing any low-level background noise that might have been inadvertently captured - for example, the hiss and hum of a guitar amp between phrases.
Don't overtook a gate's potential to help out even when background noise isn't an issue. Inserting a gate at the end of a soft pad can prevent its tail from bleeding unnecessarily into the next section, for example. Some gates are extremely quick, even capable of reducing the tails on staccato synth parts and the like. This practice also helps with definition in the mix, because the cumulative effect of cleaning up unkempt tails all over the place can be to create more space for attack transients to cut through.
If you're not careful, however, compression and limiting will raise the audibility of lower level noise that previously hadn't been an issue. In these cases, using a gate before a compressor or limiter in the signal chain may enable you to apply more compression and thus free up more headroom without clogging up the mix.
In the pursuit of headroom, you'll find that many subtle techniques in combination tend to work better than a single loudness plug-in or the like. One often overlooked technique Is simply the automation of individual volume faders.
Sometimes you'll want a new sound to burst in with great impact so that it's noticed, but it doesn't necessarily have to remain at that level. By the same token, just before you introduce a new sound, there's no shame in dragging down the volume faders of other sounds to make space for it as well.
Aim to use sympathetic volume automation in such a way that nobody would notice that the faders are moving. In doing so, you'll both free up loads of headroom and improve the tightness and clarity of the mix.
You might even decide that it's OK for a sound to enter far louder than usual, so that it drives a bus compressor if you're using one. This can add lots of excitement, especially in heavy mixes. You can then gently tuck it into the mix before the next sound is introduced. You'll be surprised at how the listener's ears will follow a sound that starts with a high impact, even If it's not mixed overly loud for the majority of the track's duration.
Loudness Tips and Tricks
START AS YOU MEAN TO GO ON
USE REFERENCE MATERIAL
Prevention is the best cure for loss of headroom. If you're serious about getting the most apparent level out of your mix then it's important to be conscious of the different things that contribute towards peak volume. Begin making headroom-optimizing decisions as early on In the creative process as possible. Make it your mission to defend that headroom in as many ways as you can think of.
LEARN THE NUMBERS
You don't have to reinvent the wheel to compete with the levels of your favorite mixes: you just need to study them and compare their techniques to your own. Keep high-quality reference material close at all times. If you're ever unsure about a decision and how It might affect the overall loudness of the track, check out how your reference tracks do things.
CREATE SPACE FOR TRANSIENTS
Many producers swear by keeping a record of important statistics and figures. What peak and RMS levels worked for your drum mix last time? How loud was the snare in relation to the kick? Where does the bass peak? Record the answers to these questions If you want to learn quickly from your successes and consistently hit those levels.
TAKE ADVANTAGE OF VISUAL CUES
In a busy mix, even sharp attack transients can be very difficult to hear. One of the factors that contributes to our perception of a transient is the level of the sound that comes directly before it. You can add bite and clarity to a transient without increasing its peak level by simply Inserting a tiny amount of silence or fading out the sound that precedes it. If It's quick enough, the ear won't notice any silence or fade, but the transient will cut through the mix better.
FILL UP YOUR BREAKDOWNS
Oscilloscopes and spectral analyzers are fantastic for learning about how sound works and will often expose headroom-munching problems that might otherwise have been very tricky to detect. Spectral editors such as Image-Line Edison, Adobe Audition 3, Photosounder and iZotope RX take this concept to extremes with their three-dimensional 'view' of sound.
Breakdowns can be troublesome. These sections- generally thought of as breathers - tend to be made up of tar fewer sounds than the full mix sections. Don't be fooled - the number of sounds is not what determines how loud the overall mix can be, and a quiet breakdown creates Impact when everything else comes back in. Fill out the frequency spectrum to keep it from sounding too weedy.
Ironically, silence is one of the most powerful tools available for creating the illusion of a ridiculously loud soundstage. It's all in the contrast, so It doesn't even need to be pure silence. Use silences and brief quiet moments as intervals between loud sounds, giving them even more size and intensity.
LOOK AFTER TRANSIENTS
Smashed transients are often the most obvious sign of sound that's been put under too much pressure to be loud, so do whatever you can to protect and enhance them. Always pay close attention when applying any effects, because If you lose your transient clarity, the mix will likely sound forced or squashed.
BROADEN THE SPECTRUM
When a sound comes from a source close to our ears, It has much clearer top and bottom end than the same sound from a distance. So, to give a sound presence, make sure it has clear highs and lows. Your goal should be to give the overall mix that quality, though not necessarily the individual sounds within it.
Test different plug-Ins and techniques. If you're not sure which effects chain will be most effective in any given situation, try as many as you can. You'll learn so much from that you'll become better at making decisions that prevent headroom loss and maximize loudness and clarity in the first place.
Sometimes you'll want to replace a sound with an alternative - e.g., switching from one bass tone to another. In these cases, you should aim to keep these sounds similar in terms of properties. Their frequency content should be well-balanced, and their peak and RMS levels should be a close match.