Why Levels Matter

At it's most basic, mastering is simply the process of arranging the right tracks, in the right order, with gaps that work and neat tops and tails (starts and ends).

As soon as you start doing this though, you'll soon notice that there are differences between songs - of level, EQ and dynamics. Even if you recorded and mixed them all in the same place.

And that's exactly as it should be - mixing is a time for balancing the parts of a song, whereas mastering is the time for balancing songs against each other - balancing the parts of an album.

So the "next stage" of mastering is to improve on these balances. And the first thing to balance is the level. Without balancing levels, any other comparisons you make aren't useful.

(Notice though that I said balance levels, not match them.)

The question is, where should the average level be ? How loud should the loudest song be, and how quiet should the quietest be ? And how do we do it ?

When I started mastering, I was taught to balance levels using a VU meter - a needle that indicates something approximating to the average or RMS level of music, which it turns out is a pretty good indicator of how loud it sounds to us.

VU meters have other advantages - they're more sensitive to bass, which agrees with the way we hear music - and they're more sensitive at the centre of their scale, around the "zero" area, which makes them useful for hitting that target level.

They're analogue though, so that "zero" level needs calibrating. The question is, how ? To what ?

In the beginning

When I started mastering, the answer was that 0VU was calibrated to -14dBFS. So, if you played a test tone at 1kHz peaking at -14dBFS, it would give a steady reading of 0VU. And since when mastering we commonly allowed the needles to reach one or two dBs above 0VU at the loudest moments, that meant we were mastering music which had about 12dB headroom above the average level before the peak level would digitally clip.

Nowadays that music would be measured as being Min PSR 12 using my Dynameter plugin, or having a maximum short-term loudness measurement of -12LU using one of the new LUFS loudness meters.

With this standard for the mastering level, it was relatively straightforward to master music - balanced EQ and gentle limiting was usually all that was needed.

Times changed, though...

Some time around the year 2000, I decided to re-calibrate my VU meters to read zero with a test tone at -10 dBFS. So if the VU maxes out at +1 or +2 at the loudest moments, there's about 8dB peak headroom before the music clips, and it measures Min PSR 8 on Dynameter, or a maximum short-term reading of -8LUFS on the newest meters.

This change reflected the general trend of mastering at higher average levels. The temptation to go a little louder so your CD sounded slightly better than any other proved irresistible to many mastering engineers.

You can't achieve those kinds of levels without carefully chosen compression and limiting settings - but you can still make great-sounding, dynamic masters that sound perfectly loud enough in most listening situations.

Then times changed again...

By 2010, it had become commonplace for music to be mastered at Min PSR 6 or even Min PSR 4. At those levels, the VU meters would be "pegged" even at my new calibration level. The only way to get them to show usable readings would be to calibrate them to read 0VU with a test tone at -6 dBFS - a change in calibration level of a massive 8dB since I first started mastering.

But I never did this, and I don't recommend you do, either. To achieve those kind of average levels on a digital format, you need to heavily squash and even distort the music, and there are no musical benefits, in my opinion. I also now recommend avoiding True Peak levels above -1, to reduce the risk of extra clipping being introduced by lossy dat-encoding further down the line.

In fact, I've found that 0VU @ -11dBFS (Min PSR 8 or a maximum short-term level of -9 LUFS) is an excellent "sweet spot" for many genres of music, and with only a couple of exceptions I've resisted the temptation to master significantly louder ever since.

But how loud do we listen ?

So much for choosing your calibration level. Depending on your taste, you can set your 0VU level wherever you like: -14 (Min PSR 11), -11 (Min PSR 8) or -6 (Min PSR 5) - or anywhere in between.

None of this will make much difference though, without the right listening volume.

If your mastering playback volume is too loud, you'll be tempted to choose lower levels. If it's too quiet, you'll tend to keep pushing the level louder.

The solution is simple - once you've decided your target average level and calibrated your loudness meter, just choose a listening level that's comfortable for long listening periods, and stick with it.

Choose a group of reference tracks, balance their levels using a calibrated VU or other loudness meter, and then pick a volume where they sound as loud as you would sensibly want them to be.

This is your "mastering level".

You'll know if you've got it wrong soon enough - too quiet and you'll always be wanting to push the level too high above your chosen reference; too loud and your ears will start to hurt or ring !

Why is this important ?

Listening at a fixed and known level is essential in mastering, so that you can make good judgements in comparison to everything else you work on.

By choosing a consistent mastering level, and balancing everything to that level first, you know that all the decisions you then make about level and EQ will be reliable.

And that's when you can make coherent decisions that help pull an album together, and make it greater than the sum of its parts.

Summary

It's up to you what LUFS level you master to - what your target average level on the CD will be. The higher you choose, the more compression and limiting you'll need to use, and beyond a certain point the quality of the results will begin to suffer.

My recommended maximum is average Short-Term loudness of around -11 LUFS, peaking up to -9. That's aiming for a Min PSR 8 on Dynameter, or no less than DR 8 on the TT Meter.

And my personal preferred way to achieve these results is to calibrate an emulated VU meter to 0VU @ -11dBFS, and allow it to max. out @ 1 or 2 dBs above zero at the loudest moments.

Then choose a listening volume where this is comfortable for long periods, where the loudest moments are massive and satisfying but the quiet details are clearly audible, and you'll be off to a excellent start making great mastering decisions for your music !