What is Sidechain Compression?

[guinsu]

Ok, this probably sounds dumb, but I couldn't turn up much on google and I see this phrase get tossed around a bit. What is it and where would a ME use it?

[masteringhouse]

Originally Posted by guinsu

Ok, this probably sounds dumb, but I couldn't turn up much on google and I see this phrase get tossed around a bit. What is it and where would a ME use it?

Basically a side-chain compressor uses another signal other than the main input to control the amount of compression. Often times it is used in mastering to compress the audio at a particular frequency range by EQing the original signal in a separate path and feeding it into the side chain to control level.

Very useful for things like de-essing, removing plosives and so forth. Very similar to multi-band compression, but only works on one band at a time.

[Track Rat]

Also for things like ducking. You could have a music bed going through the compressor and a voice over send going to the side chain. When the voice comes up, the music bed will "duck".

[reshp1]

Originally Posted by masteringhouse

Basically a side-chain compressor uses another signal other than the main input to control the amount of compression. Often times it is used in mastering to compress the audio at a particular frequency range by EQing the original signal in a separate path and feeding it into the side chain to control level.

Very useful for things like de-essing, removing plosives and so forth. Very similar to multi-band compression, but only works on one band at a time.

I've always been a little sketchy on how de-essing works. So you take a vocal track, EQ it to EMPHASIZE the "ess" and then feed that into the compressor to control the amount of compression on the un-EQ'ed track? Is that right?

[easychair]

Originally Posted by reshp1

I've always been a little sketchy on how de-essing works. So you take a vocal track, EQ it to EMPHASIZE the "ess" and then feed that into the compressor to control the amount of compression on the un-EQ'ed track? Is that right?

Yes, you feed the EQ'ed track into the sidechain, and the compressor channel is inserted on the main track as usual. Compressors are stupid, they react to level, not frequency. Boosting the problem freqs makes them much higher in level than the rest of the signal, and so makes the compressor react only when the selected freqs go above the threshold.

[reshp1]

Originally Posted by easychair

Yes, you feed the EQ'ed track into the sidechain, and the compressor channel is inserted on the main track as usual. Compressors are stupid, they react to level, not frequency. Boosting the problem freqs makes them much higher in level than the rest of the signal, and so makes the compressor react only when the selected freqs go above the threshold.

Okay thanks, that's what I figured but was never quite sure.

[tpreager]

Originally Posted by easychair

Compressors are stupid, they react to level, not frequency. Boosting the problem freqs makes them much higher in level than the rest of the signal, and so makes the compressor react only when the selected freqs go above the threshold.

Are you kidding??? Compressors are probably one of the best tools you can use for mixing. And you can get compressors that act on certain bands of frequencies. Of course with some over lap since a 10th order filter might tear your system apart (or maybe my system since it isn't strong enough).

Why would you want to boost the the 'problem' area anyways???

Timmy J

[kylen]

I think easychair just meant that single-band compressors don't care about frequency. The side-chain of the compressor can be tapped into so that it causes the compressor to react (compress) depending on the eq shape provided to it which simply hypes a part of the spectrum whenever that component is present in the program material. When the single-band compressor kicks in however it compresses everything at that point in time - across the entire freq spectrum. Unless the compressor itself is hyped due to some extra feature - T-Racks compressor is hyped a bit like this but not due to compression.

As far as multi-bands go I've set up 16th order compressors (96db/octave) in the DAW and it doesn't hurt - just depends on the type of cross-over character you like!

[tpreager]

Originally Posted by kylen

As far as multi-bands go I've set up 16th order compressors (96db/octave) in the DAW and it doesn't hurt - just depends on the type of cross-over character you like!

kylen,

What are you using for your DAW? I'm in the midst of looking for a new station and would like as much input as possible. I've read a bit that AMD opeteron (I think that's how you spell it) are fairly good, but I can't remember what chipset to use it with.

Thanks,
Timmy J

[kylen]

Originally Posted by tpreager

kylen,

What are you using for your DAW? I'm in the midst of looking for a new station and would like as much input as possible. I've read a bit that AMD opeteron (I think that's how you spell it) are fairly good, but I can't remember what chipset to use it with.

Thanks,
Timmy J

I'm on a P4 2.6GHz with an 845 chipset - in the midst of upgrading my chipset to get onboard firewire and usb2 as well as spdif i/o. I haven't finished yet so it's not a good time for me to recommend it...I can say I'm trying a ABit IC7-G motherboard for the upgrade, antec neopower 480w and either 1GB 2700DDR or 3200DDR I'm not sure yet. I thought I'd wait till they straighten out 64bit a little more before I consider the cpu upgrade...

[PowRGnome]

When I first read about what sidechaining is, there was an example of letting the kick determine how much compression to apply to the bass guitar, the result being (after hours of tweaking attack/release times, I guess) the kick attack getting through right before the note from the bass guitar hits you. I was wondering if anyone knows if this is the effect on Talking Head's Once in a Lifetime? It sounds like the bass just swells up from the kick attack, and it's really freaking cool, even if it is more obvious than you'd probably want on a straight-ahead rock record.