How compression auto make-up should work? I think I don't get it

Hi, new here. I’m trying the WaveLab Elements 9.5 demo for basic mastering of pre-mixed recordings. The compressor plugins (both Compressor and VSTDynamics) have an auto make-up gain button, but it doesn work as I expect.

Let’s say I have a normalized audio file with its greatest peak at 0db. If I apply a strong compression and enable auto make-up, shouldn’t I expect an automatic gain to be applied to the output in order to bring the greatest peak again at 0db?

Currently I don’t see this, if I render the master I see peaks well below 0db. If I want that I have to disable auto make-up and “guess” a manual make-up value by observing the master meter, which I prefer not; it’ll be great in this case to have a visual representation on make-up gain in the UI, for example by translating up the compression graph so I can see when I’m safe or when I risk clipping. In alternative, I should render the compressed audio in a new file and normalize that, but this ruins the mastering workflow.

I’m sure my concers comes from seomthing I don’t quite understand about the auto make-up concept. Am I right? Thanks.

Auto Makeup gain can’t calculate this for you but you could manually fine tune the makeup gain and then use a peak limiter to prevent the peaks from exceeding 0dB.

Also, typically in mastering now we want the peak levels to slightly below 0dB to prevent any clipping when the master WAV files are inevitably converted to mp3 and other lossy formats. True Peak Limiting can also help with that.

Ok, thanks, so it’s as I thought. I’m gonna guess an optimal make-up gain observing the level meters, and then chain a limiter to be “sure”.

I’ve read that during my researches, but I didn’t understand how and why MP3 compression can have issues with 0db peaks. Did I have to care about it also if I do MP3 compression from within WaveLab built-in renderer?

Thanks for the reply.

Basically, anytime you encode WAV/PCM audio to mp3 or other lossy formats, the peak levels will have a slight increase. It doesn’t matter if you render directly to mp3 from WaveLab, or render WAV files first and encode to mp3/lossy with another app.

Or what I was getting at is if you are releasing the audio as music on iTunes/Spotify/Amazon/YouTube/SoundCloud etc, the master WAV files will eventually be subject to lossy encoding and the peak levels will increase slightly.

Typically, the lower the bitrate of the lossy files, the more the peaks increase.

Got it. What could be a safe value, considering 90% of the time I’m exporting 320kbps MP3s which I host myself? I mean, are we talking about -0.1db or -1db?

It really depends on the material and how loud you are pushing it on average. Many mastering engineers use -1.0dB as the peak ceiling but some still use -0.2dB and don’t care about the peaks/clipping.

It also depends on what encoder you use. Sonnox Pro Codec is an app that will let you offline test your WAV files through a variety of encoders and check for peak levels.

Or, you can always render to mp3 and then open the mp3 in WaveLab again to see the peak levels and then go back and make adjustments if needed and render the mp3 again.

For 320kbps mp3, -0.5 or -0.7 is probably safe in most cases but there are too many variables to give you a definite number.

Right. Thanks again.