When we’re mastering our music, we typically try to make our song(s) as loud as possible. Our ears (and those of our listeners) interpret louder as having more energy and consequently better. When we drive our mixes too loud, too “hot”, we run the risk of clipping and distortion down the line when our music is played on different platforms and different speakers. Using true peak limiting before you bounce your master will prevent that, so let’s talk about what this is and how it works.
dBFS vs dBTP
dBFS is an abbreviation for decibel full scale and is typically the default setting on our limiters.
It’s measured in negative values (-10dB being quieter than -5dB) relative to 0dB, the max in the digital realm. Exceeding the max means clipping or unwanted distortion. What should be a smooth waveform with a curved peak instead gets shaved off, resulting in a flat peak which distorts:
This is why limiters exist, to place a ceiling at 0dB at most to prevent peaks in your audio from exceeding this and clipping once it gets to an analog playback device.
A digital audio converter, or DAC for short, is used to convert the digital format of your music to analog so that it can be played back. Digital samples are converted into smooth analog waveforms which can be played back on the speakers you’re using to listen to the music.
When this conversion takes place, the output signal can be louder than the input by way of how this conversion works, particularly on a louder master.
Let’s say you bounce your master track with a limiter or maximizer set to peak at 0dBFS (decibel full scale). In the digital realm, this will keep the master from clipping by keeping the signal from exceeding 0dBFS even on peaks.
Even though we’re not clipping, if we driving that limiter harder, meaning the peaks are frequently hitting that ceiling in quick succession, this can cause a problem when the signal is converted to a smooth waveform.
If you picture the waveform as moving up and down with the level, you get a straight flat line when you are hitting that 0dBFS ceiling consecutively again and again.
To accommodate for this, the DAC creates something called an inter-sample peak, momentarily pushing the level higher than it existed digitally in order to create a smooth waveform for analog playback and avoid that
This pushes that level above 0dB and ironically can cause distortion upon playback. The more flattened peaks which exist alongside one another , the greater the inter-sample peak(s) will be, and more likely noticeable distortion will occur.
How do we avoid inter-sample peaks?
True Peak Limiting
Enter dBTP. Rather than decibel full scale, dBTP stands for “decibel true scale”.
Most limiters and maximizers have a feature to specify in terms of dBTP when setting the ceiling or max output level.
With your audio’s peaks in mind, this estimates what the analog level will be after DAC.
You’ll notice if you toggle this setting on, the output level gets a little quieter. This is a more conservative approach to whatever ceiling you set on the limiter and mastering with it on is a more reliable way to avoid clipping as part of the DAC process.
So you might be thinking, “can I set my ceiling to 0dBTP without issue?“.
Unfortunately, there’s one LAST little bit to keep in mind.
It’s often safer to set your ceiling to -1dBTP, because when you upload your music with a distributor like Distrokid or DittoMusic to get your music in Spotify, YouTube, Apple Music, etc., your music may AGAIN be turned up more than you anticipate.
This is because they use different softwares to encode and compress your music to more efficient file types. This saves on bandwidth when people are listening back to your music on these platforms because the file sizes are much smaller and more practical for streaming.
When a WAV is converted into a compressed file type like an AAC, level increases can occur as a byproduct of this conversion, as well.
For this reason, it’s a good idea to set your ceiling to -1dBTP.
If your driving your limiter harder for a louder master, you might even want to drop it to around -2dBTP.
This makes sense from their perspective, they want your music to sound as good as possible (not clipping) when it hits their platform.
I find that as long as your short term meter doesn’t exceed -10LUFS, then setting the ceiling to -1dBTP is a safe target to account for any volume bumps your music will experience through software encoding compression once you release it.
But again, if you’re driving your master harder and regularly exceeding -10LUFS, you might want to drop your ceiling to -2DBTP to give your master a little extra headroom for that encoding process.
True Peak Limiting and Transients
Some mixing/mastering engineers argue that true peak limiting kills your master by shaving off your transients.
In my experience this is more the product of bad true peak limiters. I like Izotope’s Ozone because it lets you adjust how the transients are shaped (if at all) as part of the process.
Let’s also not forget that turning on true peak limiting makes the output slightly quieter as I mentioned earlier.
It’s easy to mistake quieter for worse, so make sure you account for this whenever A/B testing with it on or off.
Most of any negative reputation true peak limiting has gotten stems from those misleading points, so it’s worth mentioning as part of this discussion.
True Peak Limiting – TL/DR
The long and the short of true peak limiting is that it accounts for inter-sample peaks as part of the digital audio conversion process.
As such, using true peak limiting is an admittedly more conservative yet safer approach to setting your limiter’s ceiling which you should always use to avoid clipping when your music gets played back in the real world.
Also bear in mind that virtually all streaming platforms like Spotify and Apple Music compress your audio into more bandwidth friendly formats.
The volume of your master can increase during this encoding process, causing your peaks which didn’t clip before to suddenly clip above the ceiling you set.
As such, it’s a good rule of thumb to set your ceiling to -1dBTP and as low as -2dBTP if you have a louder master with more gain reduction (-10LUFS or louder).