Bug report – feature request: Loudness changes (stereo -> mono) in WL13 Audio Editor

[Heiko_Klueh]

The problem in audio editor: right click → Copy selection to new window
changes the loudness of the resulting files. The expected 3 LUFS difference is not maintained.

The pan law for mono-compatible stereo files (e.g., podcast voices) in Wavelab 13 audio editor conversion appears to be incorrect.

My aim: I want mono and stereo versions to have identical loudness (and vice versa) when working with mono-compatible voiceover files in the Audio Editor.

Test scenarios in the Audio Editor

Scenario 1:

audio editor → right click → copy selection to new window,
starting with a MONO soundfile

Mono → Stereo (Stereo Version): OK – playback is identical.

Stereo → Mono (Mono Mixdown): Error – the resulting mono file does not have the same loudness as the original mono file.

Scenario 2:

audio editor → right click → copy selection to new window,
starting with a STEREO soundfile

Stereo → Mono (Mono Mixdown): Error., loudness changes

Mono → Stereo (Stereo Version): Error – the 2nd and 3rd files do not have the same loudness as the first file.

Sound Forge can handle this as following:

Mono → Stereo: use both sides 100%

Stereo → Mono: use both sides 50%

It also offers various additional options for this scenario.

Questions:

Have I missed a setting or workflow in the Wavelab 13 Audio Editor that would handle this correctly?

Are there specific pan law or loudness settings in Wavelab 13 that I should adjust for mono‑compatible voiceover files?

What is the recommended approach for batch processing multiple files while preserving consistent loudness between stereo and mono?

[PG1]

The WaveLab function do a Left/Right channel mixed followed by gain adjustment so that the mixing does not cause any clipping.

I have tried the SoundForge function you mentionned, but it does not do what you say.
Since the RMS is per channel, this is even impossible by principle to have the same RMS for a mono file and a stereo file (left or right channel RMS ?).
SoundForge just applies a -6 dB on the mix. You can do the same in WaveLab by using this save option:

But the most recommended way, is to use a Loudness normalizer based on EBU-R128.
This one works both in the audio editor and batch processor. And you have also the benefit of having consistency between mono and stero, due to the way this loudness is computed.

[Heiko_Klueh]

Hello PG1,

thanks for your reply.

I uploaded a video to illustrate what I mean.

https://www.swisstransfer.com/d/ba740148-1061-4d96-abb8-c6e7cfe1e912

In SoundForge, I can even convert between mono and stereo—and back again—within the same window.
When converting mono to stereo, always select “Both Sides 100%,” and when converting stereo to mono, select “Both Sides 50%.” That way, the results are always identical.

A stereo file with 16LUFS has a measured value of 19 LUFS as its equivalent mono.
Mono is 3dB lower when measured.

[PG1]

It seems you did not read my previous message completely. I repeat:

1. There is no WaveLab error. Simply, WaveLab does it in a particular way, which has its merits.

2. I do have SoundForge and tried it: the RMS is not “preserved” when you do stereo to mono on a file where the RMS is not the same for the left and right channels (I tested it).

3. Nevertheless, you can do in WaveLab as in SoundForge (for the method on your picture ), see my previous picture.

4. RMS is not the way to go when you want to match the loudness of files. You need EBU-R128.
   RMS is mostly only interesting when you want to compare the loudness of individual channels, something EBU-R128 does not do by design. Again, if your stereo file has RMS value #1 for the Left channel and RMS value #2 for the right channel, thinking about RMS for the mono file “as for the stereo file” is not possible.

[Heiko_Klueh]

Hello PG1,

thanks again for your reply.

“Save as Mono File,” as you described, is indeed the correct approach in WaveLab.

I appreciate your advice.

This 23-second video from Scenario 01 illustrates what I had in mind as the right way to do it.

https://www.swisstransfer.com/d/ba740148-1061-4d96-abb8-c6e7cfe1e912