Can Someone Please Explain Compressors, I'm Clueless

[Talenless]

could someone please explain, or direct me to an explanation of compressors.

i have no idea:

where to place them

what settings to use

which model to use

what type of music to use them for (besides funk)

 

i sort of know how they work (limit picking dynamics to one level, and sustain the note), but i don't know why, or under what circumstances, or for what type of music one would use one.

[DeanDinosaur]

Compressors are used to reduce the difference in decibels between the loud and soft passages of music (dynamic). How they apply to guitar is different than general music applications. In general application the compressor is usually placed as the last in the signal chain.

 

How compressor control dynamic is simply by lowering the volume of the loudest part by a specified amount of Decibels. Without getting into the parameters of the usual compressor, I think it's easier to understand compression as a useful tool that can be very destructive if not used carefully. Let's say when you play the guitar softly and then play it harder the guitar sound becomes louder by 12db. You can use a compressor to lower the louder part so it's only louder by 8 to 10 db. Now the difference is smaller so the sound becomes more even and the softer parts can be perceived as louder in relation to the loud part and in general at the same peak (maximum level) the whole sound can become to be perceived louder. Now you reduced your dynamic range by 2-4db. 

 

More reduction of dynamic range reduction can make the sound lifeless. when you're using a compressor, the most important meter to watch is the gain reduction meter. If the gain reduction meter shows more than 6 decibels your risking damaging the sound. there's another parameter that allows you to make up for  the gain that was reduced to bring the sound to the same peak level as before or whatever level you find suitable. All the other parameters in general control how fast or slow the reduction happen.

 

Luckily line 6 compressor have simplified most of the parameters and combined them in one or two. Since there are no meters that allow you to see how much gain reduction happened you have to use your ears and make sure you didn't destroy the dynamic range specially if you place the compressor after the amp. 

Try placing before and after the amp or before or after the distortion and use your ears and fingers to get to  a playable sound.

If you monitor the sound using a mixer or any other tool other than the pod you can easily tell if the sound is completely squashed with no dynamic. Just watch the level meter of the mixer and if you see it stuck in a very small range or if the meters aren't moving at all,  that's an indication that you over compressed and you just removed all the dynamic from your sound. This might be useful as a special effect or specific sound but in general it's a lifeless sound...

[saTa]

Just to add to the very accurate explanation by DeanDinosaur: Compressors usually have five variables:

 

- Threshold level: Signal that is louder than this specified level is compressed, that is to say turned down

- Attack time: Determines how fast it is turned down. Long attack times let transients (picking sound, attack) slip through before turning down the volume, fast attack times can make the track sound flat

- Release time: Determines how fast the compressor opens up again after turning down the signal

- Ratio: Determines by how much the signal is turned down.

- Makeup gain: Global gain to make up for the volume loss incurred by compression (that's right, compressors make the signal more QUIET at first)

 

Example: Threshold is -10dB, Attack is 10ms, Release is 100ms, Ratio is 2:1 

Signal coming in at -12dB will remain untouched

Signal coming in at -8dB is 2dB above the threshold of -10dB. Ratio of 2:1 determines that the signal is turned down by 1dB meaning the output is -9dB instead of -8.

Signal coming in at -2dB is 8dB above the threshold of -10dB... meaning it'll go out at -6dB instead of -2.

 

So, like DeanDinosaur has said, compressors reduce the dynamic range of your signal... pushing down the spikes leaves more headroom so they're used to increase the overall loudness of a track. For guitarists, they're usually used to make your signal more even... examples: less spikey sound when strumming clean chords because the sustain is closer to the pick attack in loudness... more even transitions between solo/melody parts and rhythm chords... increased sustain (if louder signal is turned down the perceived decay time is increased)... and so on. :)

[medbad5150]

Great guide mate, I've been around a bit and that is a superb little guide,,cheers

[StephenSLR]

In general application the compressor is usually placed as the last in the signal chain.

 

Is this more true for a complete band recording?  I recall reading that music mastered after CD's became the norm was overly compressed so when CD's are played on a juke box they’re all at the same volumes.  Many complained that this method killed the sound.

 

On my Zoom effects processor the effect order can't be moved and the compressor is first in the signal chain.

 

I thought the idea was to compress the guitar’s initial signal so it enters the next effect cleaner, i.e. without wild spikes.

 

s

[Rewolf48]

Is this more true for a complete band recording?  I recall reading that music mastered after CD's became the norm was overly compressed so when CD's are played on a juke box they’re all at the same volumes.  Many complained that this method killed the sound.

 

On my Zoom effects processor the effect order can't be moved and the compressor is first in the signal chain.

 

I thought the idea was to compress the guitar’s initial signal so it enters the next effect cleaner, i.e. without wild spikes.

 

s

 

Yes.

 

That is both are true.

 

Mastering of a recording is typically a case of getting the apparent level as loud as possible so that it stands out when played with other tracks and a major part of this is Compression.  Radio Stations also apply additional eq and compression to make their sound consistent as they play music in different styles and from different periods sound similar - this often uses multi-band compression (several compressors each working independently on a limited range of frequencies)

 

From a single musicians perspective there can be compression applied at the mix stage in order to get the sound to sit nicely with other instrument - as well as simple compression or multi-band compression used at this stage you can also have ducking compression (side chain) where a different sound source controls the compression ration - for example a kick drum may be the side chain input on a bass guitar; rather than the bass smothering the kick or the kick having to be turned up, instead only for the duration of the kick being active the bass guitar is compressed (turned down) - if done subtly most ears wont notice anything other than you can hear both bass and kick clearly. With and HD500 you may choose to add a compressor late in the chain if there isn't anything else to process the sound before the audience hears it

 

But the compression you are talking about is as an effect in the "dynamics" category.  There are two reasons for doing this one is to reduce the dynamic range perhaps because sometimes it is hard to play at a consistent volume especially with clean sounds, the other is to increase the apparent sustain. This doesn't increase the real sustain of the instrument (unless gain is high enough to cause feedback) but rather as mentioned above the attack level is reduced by compression and the gain is made up which means that the sustain level is increased. So if you want a smooth very clean sound that doesn't die away quickly use a compressor early in the effects chain (http://en.wikipedia.org/wiki/Sustain).  Distortion effects also increase sustain but do it by increasing the level until the higher level signals are reduced by clipping. Don't use both Compression and Distortion at the same time as the end result is always high noise levels as the source note decays.

[DeanDinosaur]

Is this more true for a complete band recording?  I recall reading that music mastered after CD's became the norm was overly compressed so when CD's are played on a juke box they’re all at the same volumes.  Many complained that this method killed the sound.

 

On my Zoom effects processor the effect order can't be moved and the compressor is first in the signal chain.

 

I thought the idea was to compress the guitar’s initial signal so it enters the next effect cleaner, i.e. without wild spikes.

 

s

Using compressors in guitar applications by guitar players is using the compressor as an effect more so than a dynamic processor as when used over a complete mix where generally it's last in the signal chain.

 

When you use the compressor as an effect for guitar, you can get more sustain and also make the sound thicker. Using the POD HD compressors, place the Tube Compressor or the compressor of your choice before the amp and notice how fuller the sound becomes. When placed before the amp it doesn't affect the dynamic that much, and the sound remains more natural. I prefer the tube compressor in the POD HD because it has the least artifacts and sound very transparent where it's very hard to tell that you're using a compressor.  At any rate 2-4 decibels reduction is usually enough to tighten and fatten the sound, in my personal experience, any more than that seem to only add noise and suck some life out of the tone.

[Guitarmaniac64]

and tv also apply compression especially when there is commersials 

[mdmayfield]

You might find this interesting. It's the first of a 3-part video series I made on dynamics processing (a compressor is one type of dynamics processor):