Using the multiband compressor to sidechain


Finally upgraded to Cubase 8, and one of the main things I’ve been looking forward to is using the multiband compressor to reduce just the low frequencies of the bass with the kick as a trigger.

However, it’s not as straightforward as I thought, the manual doesn’t really help, and can’t find a decent tutorial anywhere - I really have RTFM and utilised the power of Google before posting this!

I have no problem sidechaining with the regular compressor - insert on bass track, activate it’s sidechain input, send kick to it. However with the multiband, you’ve also got the “SC” drop-down section at the bottom, and this is what I’m not quite understanding yet.

In order to sidechain, it seems you need to activate not just the sidechain input button at the top, but also the sidechain button(s) at the bottom for whichever band(s) you want to sidechain. OK, this makes sense, I guess you might want to have eg only one band triggered by a sidechain, the others to be triggered as normal by the signal from track it’s inserted on.

But what’s with the freq and q-factor knobs?? The manual says it’s a filter, but doesn’t say what sort - from the sound of it, I’m guessing a bandpass. The Q sounds like it’s adding resonance tho as you turn it clockwise, not narrowing the band. And what’s the thinking behind having this filter? Is it so you can use a complete drum loop as the trigger (or the entire, processed, drum bus), and just select e.g. a freq that centres in on where the kick is (so as to not trigger the compressor with e.g. the snare hits)? If I’ve already isolated the kick to use as a trigger though, what’s the point of this filter, and how should I approach setting it?

So I guess the main questions I’m asking are:

  1. to sidechain a certain band, is the correct setup to activate the sidechain input button at the top, and the sidechain button for the chosen band at the bottom (in the SC drop down section)?

  2. What type of filter are you setting the freq and Q for (in this same SC drop down section)?

  3. What exactly is the point behind this filter? Is it, as I surmised earlier, for isolating (eg) the kick out of a drum loop/bus, or does it have some application if the trigger already is just a kick?

Hope that all makes sense…


The global side chain at the top should activate an external input as you suggest. This will allow you to trigger the compressor from an external signal eg kick. The compression applied to each band can then be set using the individual controls for each band. You can use the filter to tune the response of each band if required.

If you activate the blue side chain button for a band this switches the band to respond to the normal input signal, not the trigger. The purpose of the internal side chain is to allow you to tune the input signal using the band pass filter. This is helpful if, as an example, you have a signal with a problem frequency that you want to damp down. You can tune a band to compress only when that frequency peaks above a certain level. Or you could tune other bands to compress when that frequency is present to bring it out in the mix.

Using you drum loop as an example, You could dip the bassier frequencies when mid sound plays (eg a tom) to help it come through.

Thanks for the reply, but I’m not finding the multiband compressor behaves like you say. I would have thought the sidechain button at the top was sufficient to get the external signal triggering the compressor, but honestly, it doesn’t move the meters unless I also activate the blue sidechain button(s) at the bottom. I certainly don’t see it switching back to the normal signal - are you sure about this? Also, if you then activate the blue monitor button next to it (which you can only press once you’ve activated the blue sidechain button), it’s the external signal I’m hearing (and this is when I can hear the external signal is being affected by the filter).

I get the example about the tom though, and why the filter would enable you to do that. If I’m just using a send from the kick as a trigger though, I feel like I don’t really need this filter - what I’ve found works best is just setting it to the fundamental of the kick drum (or actually an octave above, eg 87 hz if it’s tuned to F) and leaving the Q at 1 - this seems to trigger the compressor nice and cleanly.

My bad - you are right - you can only side chain off an external signal with the multiband compressor - some of the plugins have an internal side chain and I was getting confused.