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Old 02-18-2017, 12:11 AM
Pique Arestiuvee Pique Arestiuvee is offline
Join Date: Feb 2017
Location: California
Posts: 20
Default aax stereo key input workaround?

Hi I have been testing making stems for a track that has compression on the stereo mixbus and I have got a pretty close workaround but its just not quite there, hoping someone has an idea.

So lets say you have 5 stereo tracks routed to a stereo mixbus track with a compressor on it and you bounce it out. Then you want to make stems of the 5 tracks that when summed together sound exactly like the initial bounce of the compressed mixbus bounce you made.

The closest I have come to this is to create a stereo bus (call it "bus" for the sake of simplicity) and make the output of the five tracks "bus". Then create two mono aux tracks, pan one hard left and give it input "bus.L" and pan the other hard right and give it input "bus.R" and send the output of both mono aux tracks to the stereo mixbus.

Next, make the compressor on the mixbus inactive and create a mono version of the compressor with the exact same settings on each of the aux tracks. Then create an new stereo bus (let's call the bus "schain") and create a send on each of the five tracks all using the "schain" bus and make sure each send has the "pre" button highlighted

switch the compressor on the left panned mono aux track to sidechain mode and select "schain.L" as the key input. Do the same for the compressor on the right panned mono aux but use "schain.R" as the insert.

now you can solo each of the five tracks and bounce them, and when you sum them back together it should be pretty close to the original mixbus bounce.

However, in the original bounce the compressor was reacting to the internal incoming signal which was stereo, so only one process of compression was taking place. However, in the bouncing of stems described above, there are two processes of compression happening at the same time, one for the left channel and one for the right, and therefore it doesn't sound exactly the same.

I feel this wouldn't be a problem if Pro Tools had an option for stereo key input, so that the compressor would react to a stereo signal just like it does in normal, non-sidechained mode.

Is there a workaround or something I a missing here?

Do other daws offer the option for stereo key inputs on their compressor plugins?

A compromise I thought of was if I ever want to compress the stereo mixbus in the future then I should plan to only ever do it with the multi-mono version of the compression plugin, and that way I will be sure that I can easily print stems if needed. But something doesn't feel very good about that compromise since I am used to using compressors in stereo mode, so I'm hoping there is a better solution out there.


Last edited by Pique Arestiuvee; 02-18-2017 at 12:45 AM.
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Old 02-18-2017, 06:44 AM
Ben Jenssen's Avatar
Ben Jenssen Ben Jenssen is offline
Join Date: May 2000
Location: Oslo
Posts: 2,981
Default Re: aax stereo key input workaround?

I have a suggestion that I think you could try:

Instead of the two mono aux'es, make a stereo aux that has L and R centered and the fader set to -6db (to compesate for the centerpanning). No compressor on that aux.

Then set the sidechain of the mixbus compressor to one of the sides of the -6db aux. That should let you solo a stem, print it thru the mixbus with a bus compressor that reacts to all the tracks.

I might be missing something…
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Old 02-18-2017, 11:13 AM
Pique Arestiuvee Pique Arestiuvee is offline
Join Date: Feb 2017
Location: California
Posts: 20
Default Re: aax stereo key input workaround?

Thanks Ben! I tried that out but I couldn't seem to make the summed stem mix an exact replica of the stereo bus mix when trying out that method, I might be doing something wrong though.

I'm doing one of those tests where I create a wav file from the stereo mix bus like you would with a normal bounce (call it file 1) then I bounce all the stems using the method described above and sum those back together to create a new wav file (call that file 2)

Then i put file 1 and file 2 each on their own track and put the avid trim plugin on one of the tracks and click the phase invert button on it. If there is silence when I play file1 and file2 together then that means the wav files are exact replicas of each other.

The only success I have had with creating exact replicas is with the method I described in my first post. The method actually works if the compressor on the mix bus is created in multi mono mode. It doesn't work if the mixbus compressor was created in regular stereo mode.

I don't really like the idea of being forced to run a multi mono compressor on the mixbus. I don't have much experience with running it that way and from what I have read some people don't like it because it warps the stereo field in undesirable ways. Then again, some people seem to prefer it. Bottom line though is that it would be better to have the choice because I'm sure there are situations where one or the other is a better solution.

I'm reacquainting myself with logic 9 right now to see if using a stereo signal for the "key input" to the sidechain of the compressor is possible. If so, then a workaround would be to create a bunch of pre mixbus stems in Pro Tools, then import and the pre mixbus stems into Logic and create a mixbus track in logic with all the same setting as the one in pro tools, and create the compressed stems in Logic. The obvious drawback to this is you can only plan to use third party plugins that support both aax and AU, but luckily for me that is usually the case. The other drawback is it would be in the best interest to not use a lot of automation on the mixbus because that would be a pain to redraw and probably impossible to do 100 percent accurately. I wonder, if a stereo "key input" is not possible in logic, perhaps there is a daw out there that allows it?

Last edited by Pique Arestiuvee; 02-18-2017 at 11:58 AM.
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Old 03-01-2017, 06:45 AM
priorytools priorytools is offline
Join Date: Apr 2005
Location: UK
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Default Re: aax stereo key input workaround?

Hi Pique.
When I mix stems I do this ;
Mults route to aux groups, EG; Kit, Bass, Gtr, Lead Vox.
Aux groups route to a stereo aux (sub master "Sub=M=") which is where my buss compressor is.
Sub=M= routes to main out. . When it's time to print, sub=M= then routes to a stereo print track which is routed to main out.
So that's a stereo full mix. . .
For the stems, bypass your sub=m= inserts, compression and print a stereo mix with no compression. . This I call the "mix comp key".
Now make stems buss channels with auxes, EG; Kit stem buss, Bass stem buss, Gtr stem buss, Lead Vox stem buss. . Route your group auxes to these.
Make a group "stems busses" & have the inserts linked. (this isn't crucial, but I do it for ease).
Copy your sub=m= compressor insert onto the first of these stem busses. Assign a key input, eg Buss 61 & select external key on the compressor. Copy that insert to the rest of your stems busses.
Now each stem buss has it's own compressor with identical settings.
Now from your "mix comp key track" (that stereo mix with no compression), from an aux send, send pre fade to Buss 61 at -2.7 if you're using Pro Tools V 12x or -5.9 in earlier Pro Tools versions.(this is because they changed the mix engine).
Now make your stems print tracks & route your stems busses to them.. The print tracks go to main out. .
Make sure you have your "mix comp key" track fader down & you're ready to go. .

Straight on . . !
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