For a stereo Sidechain effect in Cubase you need to create a Quadro effects channel .
You are right about the group track, but ideally you want to to send your two input tracks independent of each other (use 2 child busses for each sound), so as they are not on the same audio path. Feed both these into the Quadro effect. If you change the routing mode in the effects box, move the two dots into the centre away from each other.
I'm not sure using 2 compressors is working, as the Waves C1-Sc should compress as well as sidechain when setup correctly. Monitoring the Sidechain should let you know whether it is working proper or not.
Another source of information:
\"The following example will use a kick drum track to duck/compress a bass line track:
1) Create a Quadro group (L,R,LS,RS).
2) Route the bass track to the Quadro group.
a) Open the SurroundPan window in the bass track by double-click on the pan-view in the mixer.
b) Here you must set the Mode Mo./St to Y-Mirror (By default it is set to Mono-Mix).
c) Set the grey panning balls in the SurroundPan window to 100% left and right
and pan it to L/R. This means the L-ball sits at top-left, the R-ball sits
at top-right in the SurroundPan view.
3) Route a send-slot of the kick track to the Quadro group.
(Of course you can route the kick track directly to the Quadro group,
but you won't hear the kick drum at the stereo output bus in this case)
a) Set Pre-Fader switch to ON (the \"at\" symbol).
(It is necessary to retain the control over the volume slider for the kick track)
b) Set the Send-Amount slider to 0 (CTRL left click on the slider).
c) Change the view of the send-slot to \"Routing\" (little window above the send slots).
d) Open the SurroundPan window by double-click the (now visible) pan-view in the send slot.
e) Do the same as in 2b)
f) Set the grey panning balls in the SurroundPan window to 100% left and right
and pan it to LS/RS. This means the L-ball sits at bottom-left, the R-ball sits
at bottom-right in the SurroundPan view.
4) Insert crunchessor in an insert-slot of the Quadro group
Start with the preset \"Club is pumping\" (or pull the Drive-knob to maximum)
in Crunchessor to see/hear the effect.
Choose a Side-Chain channel in crunchessor (in this case \"SC: 3+4\").
Leave the Crunchessor window open to see the effect via the gain reduction meter:
When the kick drum sets in, the bass track will be ducked/compressed according to the
compressor settings applied to the plug-in.
You can do this the same way with 2 mono tracks, although I think you could leave
the Mode Mo./St in the SurroundPan views to \"Mono-Mix\". Experiment a bit !
Addition: There's also another \"quick\" way to do side-chaining with Quadro Output-Bus instead of Quadro-Group:
1) Define a new Quadro Output-Bus and there 2 child/sub-busses (\"Stereo\" and \"Stereo (Rs Ls)\").
2) Route Bass track to \"Stereo\" and Kick track to \"Stereo (Rs Ls)\".
3) Insert Crunchessor in the Quadro bus.
You don't have to fiddle with Pan-Settings with this method but has its disadvantage in SX2
that you don't have further routing possibilities with the Quadro bus.
In SX3 you can define child/sub-busses also for groups (problem solved here).
If you want the description for Side-Chaining in SX3, go here:
http://forum.cubase.net/phpbb2/viewtopic.php?t=28660
\"