To understand how to Sidechain a compressor or any other VST in cubase, we must first take a look to how a proper sidechain works. We take a vocal stream "stereo spoken words" and a music background audio stream for this example::
We see two stereo audio streams going into the compressor (4 channels in total)...
But this setup isn't possible in Cubase, were only a stereo stream can go into the compressor (2 channels in total).
So the "Trick" consist in to split the 2 stereo channels (4 channels in total) and rejoin it and send it to two compressors in a very peculiar way:
This is the key part. You should understand this picture, and try to go by yourself...
... because a lot of group sends has to be done to achieve this. I think that you must figure out by yourself on how to do this, if you look to the attached picture may think that is a real nightmare!
Click Image to Enlarge...
This example was done with the standard Cubase Dynamics compressor and this is how it sound:
I've tried this with the TC X3 compressor also, with "the same" result.
