Mastering of stems...Advice please?

[Electric Moss]

I've been digging the forums all day trying to find a solution for this very problem using FabFilter Pro L2 with external sidechain enabled. I've tried Logic Pro X (10.8.1), Reaper (7.15) and Luna to no avail. I can successfully get the sidechain to trigger the detection circuit, but the plugin isn't limiting and it's clipping.

I've got the stem groups routed to a mix buss with Pro L2 at the very end and I have an un-limited mix as the source of the external sidechain to use against the stem printing. When I enable the sidechain during playback, the detection circuit is being triggered by the un-limited mix, but the limiter is clipping. When I turn the sidechain off, the limiting enables again.

Maybe I'm missing something here, but it's really a head scratcher. I've read previous reports of Logic latency issues potentially causing this.

As a test, I've also tried using the stock Logic compressor with limiting enabled, and the same thing is happening. When external sidechain is enabled, it clips, but it works when disabled.

As far as I can tell, I'm having the same issue with Reaper and Luna using the normal sidechaining methods, respectively.

I've got an M1 Max, Sonoma.

If anyone has any suggestions, I'm all ears

 

[Dirk Ehlert]

Lots of good suggestions in this thread already, the only way to do it is via stem limiting (or no limiting at all). I have been asked more than enough for stems = master stereo mix at 100% (as silly as that may be on its own) that I have implemented it as my general template setup. If you don't need realtime processing it's the simplest way to do via a clean print of your stereo mix from your stems (lets call that premaster print). That track will then be used as a trigger for the limiter(s). As others have pointed out , there are not many plugins capable of doing so, I think the Fabfilter L2 is the "standard" weapon of choice here.

The main principle is, that the limiter is working on each single stem but instead of listening to just the stem it's "hearing" the full mix and reacting accordingly.

You can either set the L2 onto your master, sidechained to the premaster print and then solo each stem for export, or have an instance of L2 on each stem, each of them listening to the full mix premaster print.
The latter option allows you to print all stems at once.

If you want/need this as a realtime setup it's a bit more complicated but the same principle applies. For this to work you'll need to have two exact copies in your template of your stems, on for final printing and one for feeding the premaster mix to the limiters.

It does take a little bit of tinkering to wrap your head around it but it's definitely possible to do.

Disclaimer: I do sell my main Scoring template in my shop with this exact setup of stem printing for realtime use.

Let me know if you have any questions.

 

[Electric Moss]

If you don't need realtime processing it's the simplest way to do via a clean print of your stereo mix from your stems (let’s call that premaster print). That track will then be used as a trigger for the limiter(s). As others have pointed out , there are not many plugins capable of doing so, I think the Fabfilter L2 is the "standard" weapon of choice here.

Thanks for the reply! So, this is exactly what I’m doing. I’ve got a “pre-master mix” as the external trigger while soloing and printing each stem as an offline bounce (via a SoundFlow macro I have automated).

Maybe I need to manage my expectations, but I was assuming that this would still limit at the ceiling I have set…which is working when I disable external sidechain and just run the limiter as normal on my mix buss.

 

[Electric Moss]

Thanks for the reply! So, this is exactly what I’m doing. I’ve got a “pre-master mix” as the external trigger while soloing and printing each stem as an offline bounce (via a SoundFlow macro I have automated).

Maybe I need to manage my expectations, but I was assuming that this would still limit at the ceiling I have set…which is working when I disable external sidechain and just run the limiter as normal on my mix buss.

One of my mastering friends just suggested that my error is using an unlimited stereo mix to trigger the limiter and I should try using a limited mix as the sidechain instead…

I’ll try that tomorrow and see if I’m still clipping above the threshold or not.

 

[Dirk Ehlert]

One of my mastering friends just suggested that my error is using an unlimited stereo mix to trigger the limiter and I should try using a limited mix as the sidechain instead…

I’ll try that tomorrow and see if I’m still clipping above the threshold or not.

That wouldn’t really make sense to me, because the sidechain has to work with the exact same material as the sum of your uncompressed stems. The limiting you’ll achieve has nothing to do whether the limiter is reacting to your live stems or sidechained to the printed sum of your stems, because these are both (and have to be) the exactly the same.

If you alter the side chain signal that feeds the limiter it doesn’t work anymore because then the limiter is not reacting to what is actually running through it.

Run your mix through the limiting and dial the limiter in as you like it with the desired final LUFS level etc. That is the exact same setting you use for the stem printing only that then the limiter listens to the preprint. Hope that makes sense

 

[Electric Moss]

That wouldn’t really make sense to me, because the sidechain has to work with the exact same material as the sum of your uncompressed stems. The limiting you’ll achieve has nothing to do whether the limiter is reacting to your live stems or sidechained to the printed sum of your stems, because these are both (and have to be) the exactly the same.

If you alter the side chain signal that feeds the limiter it doesn’t work anymore because then the limiter is not reacting to what is actually running through it.

Run your mix through the limiting and dial the limiter in as you like it with the desired final LUFS level etc. That is the exact same setting you use for the stem printing only that then the limiter listens to the preprint. Hope that makes sense

Someone on the FabFilter forum just mentioned that this feature may only properly work with Cubase and newer versions of Pro Tools. Logic has the proper delay compensation for the L2 to react to the external side chain, but, apparently, the limiter can’t catch up in time, which is why it’s clipping…

@Dirk Ehlert I gather you’re a Cubase guy? I would love to hear if anyone in Logic has been able to get this function to work.

 

[Per Boysen]

I too am using the "method 2" mentioned by Mihkel Zilmer, and many more as the thread continues. I like to see the strategy (signal path) as three levels: (1) All the tracks get summed into (2) a big number of group tracks further summed into (3) the actual stems-to-deliver, sums equaling the main mix.

You can have as many groups you need for setting up dynamic musical side-chaining but all groups must send to a "blind bus" that has no output, only the inserted ffL2 that the stem's ffL2s listen to at the last stage.

Over here I use VSL MIR3d for a general room ambiance and to place sound 3-dimensionally, and the MIR plugin gets inserted at the group tracks level. FX inserts before that (even send/return stuff).

One trick I learned, that hasn't been mentioned yet is to make sure you have one All Groups Master VCA fader track in the mixer. This helps when you have reached the perfect sounding mix but need to adjust the levels, scaling it to reach a certain main mix output level.

 

[Electric Moss]

I definitely appreciate all of the workflow suggestions and I’m looking forward to experimenting.

That said, I guess what I’m still trying to figure out is if the Pro L2 should be limiting at the ceiling when using an external sidechain?

As in, when sidechain is bypassed and I have the ceiling at -1, nothing clips, regardless of the gain. When I enable sidechain and solo an empty track, I can see that the detection is working, but I’m still getting clips above 0 when gain is set to the same.

Am I missing something obvious here?

 

[Dietz]

Sounds like a hidden routing error.

 

[AudioLoco]

The issue, for me, and I'm interested in possible solutions - is that it's not just a limiter.

A properly mastered track would have a limiter at the final stage but will have all sorts of other dynamic processors before it. In particular multiple compressors.
Lets' say 2 is the number (but honestly on normal mastering duties I might use 3 or more, each doing very little and having a very specific "task"):
That would mean you ideally would need to send as sidechain input: 1) the untouched mix 1) the mix with the first compressor 2)The mix with the second compressor to different busses etc etc and it would make it even more complex then what it is.

It makes it pretty messy especially when setting up parameters...

If anyone has simpler solutions for multiple compressors + limiter I would love to hear them.

For now I'm using the "compress and limit as much as possible on stem groups" method.
It will never amount to an actual mastered track ready to go out and compete with the world, but it seems the most straight forward method for me now.
Anyhow loudness isn't such a sensitive element for shows/films as it is for regular commercial releases so, even if the sum of the stems isn't pop-tastically loud, I don't really lose sleep over it.

 

[Electric Moss]

FWIW, I talked to FabFilter support about my issues and it is indeed an issue with delay compensation. It sounds like Studio One and Cubase are the only two officially supported DAWs for this feature. Some users have had success in Reaper as well, but it might require a little bit of tweaking.

Bummer about Logic, but I guess I'm going to keep playing with Reaper and see what I can do as I guess I don't mind the extra step of importing the stems to a different DAW to get this right.

 

[chrisr]

If anyone has simpler solutions for multiple compressors + limiter I would love to hear them.

Here you go. This is in Reaper, and doesn't rely on printing a mix first. It nulls to -70/80ish dbfs, typically, meaning that if someone is switching between your full mix and stems, they definitely are not going to notice the difference.

 

[Electric Moss]

Here you go. This is in Reaper, and doesn't rely on printing a mix first. It nulls to -70/80ish dbfs, typically, meaning that if someone is switching between your full mix and stems, they definitely are not going to notice the difference.

Thanks for posting this. When you tried this, was your Pro L2 clipping? I tried a similar approach and I'm having the same issue again where the Pro L2 isn't catching the peaks. The external sidechain is working and triggering and you can see the reductions happening on the graph, but the peaks are getting through. As soon as I disable the sidechain, we're back in business with limiting.

 

[chrisr]

Thanks for posting this. When you tried this, was your Pro L2 clipping? I tried a similar approach and I'm having the same issue again where the Pro L2 isn't catching the peaks. The external sidechain is working and triggering and you can see the reductions happening on the graph, but the peaks are getting through. As soon as I disable the sidechain, we're back in business with limiting.

That's the expected behaviour.

The reason it's happening is because in your mix, the other elements would naturally cancel out an element of the peaking stem(s), resulting in an absolute limit.

The answer is to leave headroom.

To demonstrate this, if you lower your idea of "full scale" to be say -5dbfs... then do stem mastering to that level...

You'll see that individual stems go above -5dbfs, but when they are summed together, the sum of the whole looks like a brick wall at -5dbfs...

Mute a single stem and the summed track will likely peak higher, not lower (although it's loudness may dip) because both the phase addition AND cancellations caused by that stem against the others is no longer happening.

It's counter-intuitive, but absolutely correct behaviour. When we combine two or more signals the sum involves both reinforcement and cancellation.

 

[AudioLoco]

Here you go. This is in Reaper, and doesn't rely on printing a mix first. It nulls to -70/80ish dbfs, typically, meaning that if someone is switching between your full mix and stems, they definitely are not going to notice the difference.

Thanks! will check it out