Mastering compression with side-chain filter

[inthecorner]

Hi there.

I was wondering if anyone here could possible help me understand the use of a side-chain filter on a mastering compressor? What is the use/benefits of such a filter and how exactly does one use it?

Thanks.

[huejahfink]

The side-chain is used to feed the level detection.
By filtering the side-chain the compression can be made to act more or less to certain frequencies.
A typical use would be to have a high-pass filter in the sidechain. This cuts out some of the bass, meaning that the compressor does not react so strongly to basslines / kick drums etc, and instead is more likely to grab onto snares or other prominent sounds further up the spectrum.
The outputted sound itself is not filtered.
I use this technique quite a bit on bass-heavy dance music where a stronger compression is required. It keeps the bottom open whilst controlling the rest.

Edit: You seem like someone that could use a good book on this kind of stuff. Would answer a lot of your questions.... Some might groan when I point to this one, but it is very popular. http://www.digido.com/mastering-audio-book.html

[inthecorner]

Originally Posted by huejahfink

The side-chain is used to feed the level detection.
By filtering the side-chain the compression can be made to act more or less to certain frequencies.
A typical use would be to have a high-pass filter in the sidechain. This cuts out some of the bass, meaning that the compressor does not react so strongly to basslines / kick drums etc, and instead is more likely to grab onto snares or other prominent sounds further up the spectrum.
The outputted sound itself is not filtered.

Edit: You seem like someone that could use a good book on this kind of stuff. Would answer a lot of your questions....

Thanks appreciate the response.
Does anyone know and use PSP's mastering compressor? Specifically on this compressor you can set the side chain lower or high frequency range. Now if someone can correct me if I am wrong. If I set the side chain to 100hz (left fader) and the top frequency range to 16000 kHz (right fader) does that mean that the compressor is compressing/acting primarily in that (between 100hz - 16000khz) range? Meaning anything below 100hz it's not going to compressor so vigorously as the rest. Is this correct? Enabling the kick or bottom end to breath a bit, right?

I hear u, I am working on getting more books on the matter. Thanks a lot again for the help.

[inthecorner]

Originally Posted by huejahfink

The side-chain is used to feed the level detection.
By filtering the side-chain the compression can be made to act more or less to certain frequencies.
A typical use would be to have a high-pass filter in the sidechain. This cuts out some of the bass, meaning that the compressor does not react so strongly to basslines / kick drums etc, and instead is more likely to grab onto snares or other prominent sounds further up the spectrum.
The outputted sound itself is not filtered.
I use this technique quite a bit on bass-heavy dance music where a stronger compression is required. It keeps the bottom open whilst controlling the rest.

Edit: You seem like someone that could use a good book on this kind of stuff. Would answer a lot of your questions.... Some might groan when I point to this one, but it is very popular. http://www.digido.com/mastering-audio-book.html

Very helpful!

[inthecorner]

On the psp mast comp there is this other button I can't find anything in the manual on: "s.c. Ext" what does it do and mean?

[huejahfink]

I've not used the PSP - but yes, that sounds about right dependent on a few things.

If your filter starts rolling off at 100hz, and the main 'oomph' of your kick drum is also at 100hz, then the kick drum will trigger the compressor as normal.

However, if the 'oomph' of the kick drum is closer to 60/70, then this certainly won't be triggering the compressor so much, because these frequencies have been more significantly reduced in the sidechain.

A sub bass note at around 40hz will be unlikely to trigger it at all.

Edit: SC Ext - I am presuming this is to use an external input to feed the side-chain. There are a number of uses for this in mixing, but in a mastering situation you would most likely be running the track signal through your own EQ set-up rather than use the inbuilt filters - and then into the external sidechain input.
Besides low and high cuts, you could also make the compressor act more on the low end of a snare by boosting (for example) 200hz in the sidechain a bit, or you could make it effect the snare less by dipping that frequency. Of course this all depends on the other frequencies in the track but hopefully you get the idea.

[huejahfink]

Originally Posted by inthecorner

Very helpful!

e- yeah sorry I have a tendency to go back and edit posts several times......

[inthecorner]

Originally Posted by huejahfink

I've not used the PSP - but yes, that sounds about right dependent on a few things.

If your filter starts rolling off at 100hz, and the main 'oomph' of your kick drum is also at 100hz, then the kick drum will trigger the compressor as normal.

However, if the 'oomph' of the kick drum is closer to 60/70, then this certainly won't be triggering the compressor so much, because these frequencies have been more significantly reduced in the sidechain.

A sub bass note at around 40hz will be unlikely to trigger it at all.

Edit: SC Ext - I am presuming this is to use an external input to feed the side-chain. There are a number of uses for this in mixing, but in a mastering situation you would most likely be running the track signal through your own EQ set-up rather than use the inbuilt filters - and then into the external sidechain input.
Besides low and high cuts, you could also make the compressor act more on the low end of a snare by boosting (for example) 200hz in the sidechain a bit, or you could make it effect the snare less by dipping that frequency. Of course this all depends on the other frequencies in the track but hopefully you get the idea.

Once again really thank u for being willing to get into this. This is really valuable cause when I master with single band comp I often find the kick disappears due to the compression and so applying the side chaining I could potentially still keep the kicks life. I gotta say it's almost like multi band comp, with a difference of-course, but in a sense you can achieve a similar result with 2 bands of compression. I just never get the kick to sound right and come out when I multiple band compress. I don't know why but multiple band comp has not really given me great sounding results. If I want a puchy kick what is the best way to maintain or emphasize the kick when mastering pertaining only to compression?

[huejahfink]

Originally Posted by inthecorner

If I want a puchy kick what is the best way to maintain or emphasize the kick when mastering pertaining only to compression?

How long is a piece of string? There are too many factors involved in most mixes to be able to say anything really worthwhile to your question other than what I have already written above.

For now, spend some time experimenting with the attack and release settings of a compressor while a track plays. For me, this was the hardest part of compression to get my head around and there's no replacement for hands-on (or ears-on) experience. This is the closest I can give you to an answer right now!

[inthecorner]

Another thing I was hoping to understand better, don't u find that when using side chaining, the lower frequencies get a bit out of control?

[huejahfink]

No. Only if they're not set right.

[heybub419]

Originally Posted by inthecorner

Another thing I was hoping to understand better, don't u find that when using side chaining, the lower frequencies get a bit out of control?

Sometimes I'll cut some of the low frequencies before applying SC compression, depending on how much bottom the material has.For example, with hip hop, there's often a LOT of low end, sometimes way too much. EQing before SC can help tame this in certain cases, and still keep the low end due to the makeup gain of the compressor.

Note that I say sometimes. As always, it's track dependent, and it may not sound too good on certain things. Something to try out though; it's helped me out quite a bit.

[inthecorner]

Thanks a lot! Single band compression with a side chain filter is quite an awesome way to master.... When setting the attack, release and threshold just right, with EQ one gets an incredibly punchy, dynamic & loud enough master. I also wanna see if I can't get similar results with a 2 band compressor.

[Odeon-Mastering]

Originally Posted by inthecorner

Thanks a lot! Single band compression with a side chain filter is quite an awesome way to master.... When setting the attack, release and threshold just right, with EQ one gets an incredibly punchy, dynamic & loud enough master. I also wanna see if I can't get similar results with a 2 band compressor.

It is a tool...but I wouldnt call it "an awesome way to master"

A 2 band compressor is not at all like compressing with the sidechain Eq-ed

[Joe_caithness]

I couldn't live without this!