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Multiband compressing WITH sidechain


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Yes, this is possible in Logic but a bit of a kludge. There are 3rd party compressors like Pro-C where this is easily done since it both side chains and you can set the top and bottom edges of the frequency zone you want to compress.


Here's one way to do this in Logic with the most control over your frequency zone of compression.


To do this you'll need two extra unused Aux tracks plus your original and sidechain tracks.


Set the output of original track to an unused bus. This will create a new aux. Create one more aux and set it's input to the same bus. So now you will have two auxes being fed by the same bus.


Aux 1 is the compression aux:


Insert one Multiband Compressor and in the MBC solo the zone you will be compressing. Set all compression settings to off - the MBC is NOT going to be doing the compression duties.


Insert a track compressor after that and side chain it to the track you'll be getting your sidechain signal from.


Aux 2 is the uncompressed Aux:


Option-Command-drag the first MB Comp over to this aux so that you will have the identical settings across the two MB comps.


Now reverse the soloed zones in the second MB Comp. (One soloed zone in the first MBC, the other 3 in the second.)


After this, it's simply a matter of setting up your track compressor on the first aux to what ever strength and ratio of compression that you need.


The caveat is that any changes you make to the first MB Comp's frequency zone must be done to the second one as well so this can be picky as you find your sweet spot. So if you have a compression zone of 100 Hz to 500 Hz on the first comp, make sure the second one is set the same. The only difference between the two MB comps is that their soloed zones must always be reversed.


Although this is complex, the use of two auxes does give you a discrete volume control over the compressed zone which you can use to fine tune your overall sound.

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Right now I tried to route the end bus via 4 send slots (pre fader) to 4 busses and than split every bus into 4 bands with an eq. But there was a lot of comb filtering going on plus the fact that Logic assigns all these tasks to one CPU core. Wich is a bitch...this system of core sharing in Logic really freaks me out.


But thanks again I will try your trick now! It might be a little better for performance...

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fader8, that looks very interesting. Gotta try that one out.


In the meanwhile, @ doppio, here's a song file for what I was describing above.....


EDIT: Note that in this song file I didn't follow my own advice - the Multiband comp that has three soloed bands does not yet have the comps disengaged. :oops: So that comp is actually compressing very slightly but you should be able to see the principal at work anyway.


To turn off compression on the Aux 2 MBC, simple move all the compression threshold sliders all the way to the top.

Sidechained Multiband comp.zip

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Thank you for that excellent trick @ fader 8 , working with it right now, the only thing is: It doesnt seem to work with PDC set to ALL...But I am working to find out why, if you are allready familiar with this problem let me know...but great work!

I replied that thread also, hope you don't mind


@ Camillo Jr, thanks for the tutorial. It works great, just one thing: Is there a difference between using Busses for this or Auxes (CPU- core assign wise and PDC wise)?

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  • 7 years later...
...for those arriving here SEVEN years after this was posted, consider the cheapest option by far: iZotope's Trash2 plugin (which you can sometimes get for $29 at JRR). In addition to all the noisemaking features, it comes with a built-in MB compressor with sidechain capability. Aces.
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