Compression & Limiting

Setting Explanation

Presets:
- Drums
- Vocal
- Bass
- Brass and wind instruments
- Guitars
- Final mix

General Tips

Setting Explanation

Threshold
The level at which the compressor will start working.

Attack
How fast the compressor will take to react to the signal going over the threshold.
Slow attacks mean early parts of the signal will pass through without change.

Release
Time it takes for the compressor to return back to normal. i.e. stops altering the sound.

Ratio
The amount of compression once the signal crosses the threshold, i.e. how much to turn the volume down.e.g. 2:1 = for every 2 db over the threshold you'll get 1 Db of gain back out.

Knee
Is the gradient at which the compression is applied. Denoted by Hard and Soft. Soft knee compression is when the compression gradually fades in. Often used for extreme \ limiting compression.

Hard Knee is often used on lower ratios, or for "brick Wall" limiting.

Most compressors come also with a Gain knob, to make up for the loss of level that compressors give.

Basic Settings
The following is just a starting point. It all depends on the instruments used and how how they were recorded. I generally, start with these settings then tweak them. Print out this page and stick the table up on the wall for reference.
At the end of the day there is no magical settings.

Presets

Drums
Start by calling up your sequencer and compressor then select your drum track. Threshold - set it to around -15dB . The ratio should be set between 5:1 and 8:1 . Set the attack to around 5ms . Release sets how long it takes for the compressor to come back to its normal, uncompressed state. With drums this has to be set pretty short, otherwise the compressor will not have had time to recover before the next kick. Set it at around 10ms , or leave it on auto. This is where we need to use the make-up gain to bring it back up to an acceptable level, this needs to be set on a personnel preference for your music, we've set it at 7.0dB .

Drum signals are often compressed due to their hard-hitting attack volumes. If nothing else, compress the snare drum, because each hit will likely peak higher than other hits. Try starting out with a ratio of 3:1, and use a fast attack and release. If the signal is still peaking, try using a ratio of 4:1. This method could also be applied to the toms. As for cymbal hits, try starting with a 2:1 ratio (moving to 3:1 if needed), using a fast attack and a slow release (to preserve the natural decay time of cymbals).

Vocal
Between -3 and -8dB is a 'standard' threshold setting. Female vocalists usually require more compression than male. Set it around - 5.5dB , with a ratio of 4:1 - just enough to stop any signal peaks filtering through. For vocals you need to use the fastest attack that your unit will allow along with the fastest release . It's better to use an auto setting for release (if there is one). Use the make-up gain to adjust the volume.
As with drums, compression is also commonly used on vocals. The ratio to start at varies for each singer, since some may be very strong and loud singers, and others quieter, having a smaller dynamic range.
Try starting out with a 2:1 ratio, with a fast attack, and medium to slow release. Keep increasing your ratio until you get your peaks under control.

Bass
The threshold should be set between -2dB and -10dB. For a more dubby sounding bass set the threshold to -9dB. A pretty high ratio is needed to prevent the bass from dominating the mix, so set the ratio to 8:1 . If there is an initial 'plucking' to the bassline, use an attack of 8ms with a release of 10ms, as this will allow the plucking sound through untouched.
A synthetic bassline needs a little less compression, Set the threshold at -4dB, with a ratio of 4:1. so set the attack at 6ms - less if there isn't a 'pluck'. Then set the release at around 10ms, or preferably set it to auto.
Try starting out with a ratio of 4:1, and a fast attack and release. I usually use the hard-knee type of compression here since bass is such an attack-oriented instrument. But if you were playing smooth jazz bass, then you may want to try soft-knee.

Brass and wind instruments
Set the threshold at -14dB with a ratio of 8:1, a fast attack of around 2ms and again a quick release of 10ms. Again, auto will work.

Guitars
For these, set the threshold at -14dB, with a ratio of 8:1. Again, if there are any plucking sounds, we don't want to compress them, so set the attack to around 4ms with an auto or very short release.

Optional :
compression ratio = around 2:1 (2 to 1)
attack time = around 3ms (3 milliseconds)
release time = around 300ms (300 milliseconds)

This depends on the type of sound you are using, but a good general place to start is 2:1 on acoustic, and maybe 3:1 on distorted guitar (although you may need 4:1 here). To get a good sustain, try a 4:1 ratio, use a fast attack and slow release. Then play the note you want to sustain, and raise the ratio until the sustain is as long as you want it.

Final mix
Set the threshold to around -9dB with a ratio of 2:1 and a quick attack and release. This will compress most of the instruments except the vocal line, which can then sit at the front of the mix. If you're after a warmer sounding compression, then feed the mix out to a distortion or amp simulation unit with a very low setting, then return it to the compressor. Using distortion helps to add harmonics which can result in a warmer sounding mix.

General Tips

Listen to the item you are compressing, with and without compression, preferably at the same volume, to see if it is really required. It may be better just to limit the peaks than compress the whole thing.

Put the compressor first in any chain of effects. It gives the other effects a better signal to work with and won't amplify any noise introduced by those effects.

Everything will benefit from a bit of compression on them.

On percussive sounds use a longer attack time, so most of the sound passes through before the compressor kicks in. This should give the sound a more pronounced attack.

Setting a fast attack and release time can give a pumping effect (Used a lot in dance music).

Female vocals allegedly require more compression than male vocals?

Vocals. For an etheral effect apply extreme compression to the vocals, then filter or EQ out the bass and most of the midrange (below 1kHz).

Multi band compression on vocals can be useful to change the timbre of the vocals, e.g. more compression in the high end to give a vocal a sizzle, or to accentuatte a raspy voice.

A �Frequency Selective Compressor � (De-esser) is a special compressor that reduces the level of a very narrow band of frequencies. It ' s very useful when a singer has a strong, sharp, sibilant �S� to their voice. Typically in the 5-8k range. When 5-8k exceeds the threshold, it reduces strong, sibilant "S's" without affecting the rest of the word.

Compressors with auto release can be useful to maintain the dynamics of a track.

Drums. For a distorted U2 type sound. Set a compressor threshold to -50 db and a ratio of 20:1 with fast attack and release.

Sub group your drums to a stereo channel, apply stereo compression to get the drums pumping.
As above but add some modulation effect (flanger, filters, phaser etc) for a bizarre effect.

Multi band is useful, since a lot of the compression occurs from lower frequency noices. Giving the lower frequencies more compression can give a tighter louder mix. Alternatively, I suppose just up the compression on low frequency instruments?

As with all effects check the sound with and without the effect to ensure you are not making things worse.

To 1.EQ then Compress or 2.Compress then EQ. Try both, since you will get different effects.
2. usually works out better.

Compressors can bring up the noise level, so gate the sound prior to compression.

If your compressor has a side chain, you can use it to trigger instruments from drums.
e.g. you can tighten up a bass part by triggering it from the bass drum.
A similar effect can be used to trigger a gate on a distorted guitar triggered from a hi-hat.

If possible, put the uncompressed sound on a spare track--it may save your life. If there's any "rule," most engineers would agree to save the decision on drum and percussion compression until mixing. There are always exceptions--every piece of music is unique. Just remember, you cannot undo the damage of overcompression, so be careful about compression during tracking.

The better the bass player, the less compression you will need to use, and the greater the chance that compression will "choke up" his sound. Get to know the sound of your instrumentalists. What is your mixing philosophy? Are you trying to capture the sound of your instrumentalists or intentionally creating a new sound?

An engineer once told me that the best sound he got was the monitor mix on the recording day. By the time he got through slicing and dicing and remixing, all the life was taken out of it (what I call the loss of microdynamics) .
So remember the sound you got during the recording...did you lose the magic in the mix?