Are you mastering your own material, do you employ automated online mastering services or will your mix be mastered by another mastering engineer? Whatever the case, you can achieve a healthy loudness way before you (or they) insert a limiter at the and of the chain.
Most of the loudness is actually achieved in the mixing stage, but not by putting a limiter on the master bus and calling it a day 😋 You can get much louder and cleaner mixes by preparing for that stage and make the limiter's job easier if you follow good practices.
1. Reference and target loudness
First of all, you might have heard of the "loudness war". It means making each song as loud as it can be, regardless of the damage that does to the music. This is now largely a thing of the past. There is simply no point in going as loud as possible anymore.
Today's name of the game is the "target medium" nominal loudness level. Don't start by pumping that beat into the limiter blindly but instead aim for your loudness target. Even better, have a reference track handy and imported into your project in one of the A/B comparison plugins. This will keep you from overshooting and killing the song in the process.
Today listeners consume music primarily from streaming services. In general, these have a target loudness set to a pretty smart and sensible value. You can google for the latest numbers, as they do still change from time to time.
On average, it is roughly where the point of diminishing returns occurs when trying to achieve even louder masters. In other words, if you go far beyond the -13LUFS, you have a good chance to make it sound worse. The different platforms normalize the files on upload according to its internal scale and that can hurt the loudness severely.
2. Obsess over low-end 🔈🔊🔈
Nailing the low end makes the song groove. It makes you want to get up and dance in the middle of your office! And it also makes for louder sounding masters at the same measured LUFS!
Because of math and physics and all that nerdy stuff, low frequencies carry the majority of power. This is why they eat away at the headroom and loudness the most. It just takes a lot of energy to move all that air.
Low-end clarity is also the plague of bedroom and basement studios. Good bass trapping acoustics can cost an arm and a leg. In such environments, a good pair of headphones is your best friend. Just keep in mind that you have to really know your pair well to EQ the music instead of the headphones' frequency response.
Unnecessary Content is the enemy of Loudness
You can "nail" the low mostly by meticulously cleaning the 20-200Hz region of all unnecessary content.
A kick drum usually sounds "thumpy" if it has too much content in the 100-200Hz region. Taking care of that leaves space for the snare drum's punch as well as bass (guitar or synth) harmonics. Those are crucial for translation to smaller systems and achieving more loudness on them as well.
Also, if your bass track goes down all the way to 11(Hz), consider high-passing it at 20-30Hz. Remember - the lower the frequency, the more headroom it will take! To avoid conflicts with the kick drum or even a low-tuned snare drum, either arrange the lines so the bass makes a break where the kick hits, or use ducking/sidechain compression.
If you use those techniques, you won't have to boost the lows for each competing element as much and save a lot of headroom. Your limiter will be ever so thankful.
3. Take care of peaks 📈
It's far easier and more transparent to take care of the sharp, loud peaks at the source than with a stereo limiter on your master channel. You can do that with several tools:
Limiting - I bet you never saw that coming 😛 Using a limiter on a single source like a snare drum will allow you to fine-tune its parameters so it will work well and sound good for that particular sound and not duck the whole mix when it triggers.
Saturation/clipping - Those processes are usually linked with color, distortion, and harmonics. But it might surprise you how transparent they can sound if used carefully! Most of us even like some additional character and punch, so why not kill two birds with one stone?!
Slew-rate limiting - Yes, I have to bring this up even if you've probably never heard of it. Slew-rate is a property of (usually) amplifiers that tells you how fast it can change its output voltage. In practice, this translates to a level-dependent high-cut filter. It can be used as a very transparent tool to tame very sharp, bright, "clicky" transients.
Some analog electronics have this property inadvertently built-in with the chips that they use. Others, like Elysia's museq for instance, have it as a feature. In this particular unit it's called "Warm mode". On the software side, I can't think of any plugin that would do that explicitly (except for the museq of course). Some of them might be doing it under the hood, but I've yet to come across one that has "Slew rate limiter" written on the UI.
4. Look for resonant content 📳
Everything that you can get rid of will leave more space for the useful stuff.
We're delving deeper into the mix now. It's a tedious job to go from track to track and listen for any ringing at weird, harmonically unrelated frequencies. The trick is to only get rid of the ones that have nothing to do with the tone or chord that the instrument is playing. These sounds still need the energy to be reproduced and are thus eating away at our loudness.
One example is the ringing of an acoustic guitar's string ends behind the nut - those usually don't correlate with any chord that you play. If you haven't noticed it while recording, try and get rid of them with sharp, tuned EQ cuts.
Similar stuff happens with pretty much all acoustic instruments and any source recorded with a cheap or inappropriate microphone. Taking care of it while recording or mixing is tedious, but you will be thankful more and more as you progress through the mix and mastering stages for the song.
5. Consider frequency masking 🎭
When you've eliminated the weird, unrelated ringing present in some of the tracks, it's time to put them all together. It's similar to "nailing the low-end", but applied across the spectrum. Find a way to puzzle the tracks in the frequency spectrum so that none of them sounds unnatural but they still leave space for one another.
The good news is, most of the history proven combinations of instrument arrangements work in your favor. It's no coincidence that you (usually) don't have three people playing the bass guitar in one band or a whole orchestra of piccolo flutes (please God don't...).
But even with diverse sounding instruments, you can still get congestions, especially in the low- and high-mids that our ears are most sensitive to.
So how to go about that? Switch between the tracks and listen for content in the same range. For example, a distorted synth lead and the vocals might both be strong in the 2-3kHz range. If they both appear in the song at the same time, they will cause harsh and annoying buildup in that part of the spectrum.
Either make the vocals smoother and more present by cutting at 3kHz and boosting in the 5-7kHz range or cut a hole with an EQ in the synth lead at 3kHz. The decision is yours, but any of those should make them both sit in the mix better.
All that juggling will result in is a mix where the elements are clearly perceived at lower levels! This allows for pushing the whole mix further up without pulling up congestion and mud.
Although we just scratched the surface of those techniques and skills in this blog, they can be mastered with practice and yield surprisingly robust mixes that translate really well.
Now go and try them on a song that gives you the most problems on getting a healthy, competitive loudness and see if you can extract some more with the tips above without destroying it. I wish you good luck and happy mixing!