The Prages "What does a Compressor do" tutorial

[Mark Wein]

These are all taken from another thread but its all Prages' work...

Compressors basically take the peaks, level them off, then bring everything else up in volume by however much you leveled the peak. It makes the loud parts quieter, allowing you to make the quiet parts louder. It squashes your signal.

Here's a wave file. The first one is uncompressed. The second one has a generous amount of compression. They both peak at -1 db, but you can see in the pic that the compressed one's quiet parts are louder and its spikes are evened out.

No compression:
http://www.thewindtunnel.com/Clips/Compression/NoCompression.jpg

Lots of compression:
http://www.thewindtunnel.com/Clips/Compression/Compression.jpg

The sound files sound like crap because I was intentionally playing with too much dynamics, and I overcompressed the compressed file to prove a point. Let me check to see if they uploaded okay (I doubt it) and I'll post the sound files if they did.

As I suspected, they didn't upload well, but here they are anyway. Ignore the hiccups and the shitty playing, and just listen to the dynamics of each track.

No Compression (http://www.thewindtunnel.com/Clips/Compression/No%20Compression.mp3)

Lots of Compression (http://www.thewindtunnel.com/Clips/Compression/Compression.mp3)

About the 'compression increasing sustain' thing, here's how that works.

When you play a note, the loudest part is the attack. As the note sustains, the intensity and volume fade out.

So, the note would look something like this. (excuse the crude MS Paint rendering).

http://www.thewindtunnel.com/Clips/Compression/Uncompressed%20note.JPG

Now, if you set your compression threshhold below the peak of the note, it'll chop off that peak, but not effect the signal below the threshhold.

http://www.thewindtunnel.com/Clips/Compression/Compressed%20note.JPG

Now, if you use the compressor to raise the level back to the original peak, you can see that the peak will last a lot longer, and the decay will be louder.

I can't figure out how to show that in paint, but if you could take the uncompressed pic and overlay the compressed pic with the threshhold line where the peak line is, that's what the compressed note would look like after the gain make up.

[huskerdude]

I hope you don't mind me adding onto this, Mark, but I thought I'd drop in a couple notes on compression on drums. Let me know if I should move/remove it.

Most compressors also come with "attack" and "release" knobs. These can be extremely useful for shaping the sound coming out of the comp, especially when it comes to drums.
The Attack control determines how long after the sound crosses the threshold the compression itself will kick in. It's essentially like a little predelay that allows some uncompressed signal through before kicking on the effect and bringing down the level. This control can be a lifesaver when you're working with somewhat dull, lifeless drums or loops. By setting the attack a little bit higher than usual, you can effectively "punch up" the drum hit by allowing more of the initial signal to pass through, then letting the compressor rein in the rest of the hit.
The release control determines how long the compressor will stay active after the signal crosses the threshold. The majority of the time for drums, you'll want to set it to a point where the signal is being compressed for the entire duration of the drum hit, so ensure everything is back to zero by the time the next hit comes along. However, you can a great "bloom" effect (this is especially fun with overheads/cymbal samples) by setting the release very very fast. This makes the compressor stop compressing before the sound has decayed naturally. Think Flaming Lips drums, as a somewhat extreme example of this sound.
I'll try to cook up some examples in the near future to better illustrate these concepts.

[Mark Wein]

I hope you don't mind me adding onto this, Mark, but I thought I'd drop in a couple notes on compression on drums. Let me know if I should move/remove it.


Actually I think its great that you contributing to the thread. Compression is something that most guitarists really don't have a good understanding of. Even with my experience its a little bit of a murky subject biggrin

What about compression ratios? In the picture below is the compression set 8:1 or 8db of compression per 1db over the threshold?

http://i97.photobucket.com/albums/l230/markwein/compressor.png

[huskerdude]

An 8:1 compression ratio would mean that a signal at 8db over the threshold on input would be 1db over the threshold at output. A signal at +16 would leave at +2, and so on.
http://i83.photobucket.com/albums/j294/hudu81/ratios.jpg
As you increase the ratio, obviously the "effect" increases, and you'll begin to hear the compressor working a lot more. A very, very common issue with novices is that once they figure out how to compress stuff, they'll squish everything to death. You keep turning up the ratio and turning down the threshold until you can hear the effect. It sounds really cool and huge when you do that on one track, but if you're doing it to 8-10 tracks in a tune, it's going to end up sounding thin and noisy. Be careful about compressing things too much. Unless you're doing some pretty specific and more advanced tricky stuff, the less you "hear" the compressor, the better.

[Mark Wein]

Thanks! I've never understood exactly how that works...I'm actually tracking the vocals on my tune right now and the higher ratios don't sound very good to me with what I'm doing.

I'm also fighting an 8' ceiling that is making everything sound boxy....I wish I could track this stuff in the studio down the hall with the 10' ceilings but I'm just not set up for it at the moment...

[telecaster911]

This...

http://www.audiomelody.com/1/Articles/How-To-Use-a-Compressor


:aok:

[Prages]

I actually compress my vocals at an 8:1 ratio with the threshhold around -20db. :o I've found that when you get into ratios that high, the quality of the compressor makes a huge difference. I'm using URS compressor plugins, which are really good ones. I can't get away with using that much compression with the freebie compressor plugins that come standard with Cubase.

[Dexter Inferno]

One thing I've become quite good at is compressing in series (very useful especially on vocals).

I'll often use one compressor first with a low ratio (say, 3:1), longish attack, and long release. Set the threshold quite low so it compresses around 4-5 dB at most. This helps give the source material a bit of extra "punch"/attack.

After that I'll insert another compressor, this time I'll set it with a high ratio (8-10:1 or higher), very fast attack and release - making it work like a limiter. This is used to catch any errant peaks and spikes that gets through the first compressor.

The result of this approach is a track that doesn't sound very compressed, but is still smooth as fook. :-)

Sometimes a track will need a full-on compressor assault.
In that case, enter the Blockfish plug-in. This one is absolutely awesome at vocals and smashing room mics and such. And it's free love0

Even then, sometimes I'll have a really troublesome vocal track that just won't sit right, after compressing. This is where I get ahold of the Waves C4 multiband compressor - which never fails. If you're careful about not overdoing it, that compressor can be a lifesaver when all else fails.

[Prages]

I also sometimes set up more than one compressor on a source. I mostly do it when mastering though.

I'll often use the old Waves UltraMaximizer on the master bus as a multi-band limiter when I do my mix down. I set it fairly low...something like -3 db threshhold. Then once I've got the stereo mix, I'll run it through my mastering software, whose chain is EQ, Compressor, Multi-Band Limiter, Output limiter. I use really low compression settings on all of those limiters, but the overall effect is a very punchy track that, when done right, still has some dynamics.

[Mark Wein]

I actually compress my vocals at an 8:1 ratio with the threshhold around -20db. :o I've found that when you get into ratios that high, the quality of the compressor makes a huge difference. I'm using URS compressor plugins, which are really good ones. I can't get away with using that much compression with the freebie compressor plugins that come standard with Cubase.

I'm going to try this today and see what happens...

[Prages]

I'm going to try this today and see what happens...

Now that I look at an old screen capture, here are the settings I use for lead vocals most of the time.

Ratio: 8:1
Threshhold: -20db
Attack: 1.5 ms
Release: 250 ms

Then adjust your gain makeup to bring the peak back up to about -1 db or so.

[Mark Wein]

Cool!

I'll probably try a different plugin...I was just using the one in the picture above because it was the most "caveman" of the ones I have available...

[Prages]

I was looking at that. I don't see a threshhold knob on it. I'm assuming it's either a fixed threshhold, or the 'input' knob acts as the threshhold.

This is the one I use.

This is actually the preset I use for vocals.

http://www.thewindtunnel.com/Recording/VocalReverbCompression.jpg

[Prages]

I don't know what I was looking at before...the threshhold is -20 db, not -15. :facepalm:

[tamoore]

I set the threshold to whatever sounds good, not to a specific db number. On vocals, I set it so that at my absolute softest passage the signal gets no reduction, and everywhere else it's being compressed. I also set it to 10:1 because I can't sing for shit and I have no control, so I'm all over the map. This setting helps bring me to the middle. :o

Them USR compressors sound pretty nice if you can afford them......:o


:cry:

[Prages]

Them USR compressors sound pretty nice if you can afford them......:o


:cry:


They sound REALLY nice, and I got them for FREE. :o

[Kerouac]

I was looking at that. I don't see a threshhold knob on it. I'm assuming it's either a fixed threshhold, or the 'input' knob acts as the threshhold.

This is the one I use.

This is actually the preset I use for vocals.

http://www.thewindtunnel.com/Recording/VocalReverbCompression.jpg

That is an EXCELLENT plugin. It's actually the one I used for my Iron & Wine's "Such Great Heights" cover.

I also have the old Kjaerhous Gold series and some of those are fantastic... they're the basis of what Cakewalk modeled their Vintage Channel 64 on.

[Prages]

That is an EXCELLENT plugin. It's actually the one I used for my Iron & Wine's "Such Great Heights" cover.



Pretty much every track I've recorded in the last 3 years has that plug all over it. It's the most transparent compressor I've ever used. You can compress the shit out of stuff and never really hear the compressor. I love it.