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Old 2005-03-31, 19:24
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A good article on compression techniques

This Is A Nice informative find! Enjoy


MASTERING COMPRESSION
By Noviss
noviss900@hotmail.com

Many people fail to realize how important using compression actually is. Whether you're recording or mastering, you need compression. Whether you're independant or professional, you need compression. Whether you're selling 500, or 500,000 units, you need compression. Every album you've purchased has used some form of compression. Music just wouldn't be the same without it, so take a seat and prepare to enter the world of compressed recording.

Although I'll be giving you some numbers and ratios to use, these are just guidelines, nothing more. You won't find the perfect compression guide because such a thing doesn't exist. You must realize that everything varies per track. Not all music is the same, and in that sense, not all FX are going to be the same.

Note: Because hip-hop is one of the most heavily compressed forms of music, this article is written in the perspective that you'll be applying the following techniques to a hip-hop track.

What does compression do?

com?pres?sion
n.
1. The process of reducing dynamic range of a given audio signal by making the loud parts quieter and the quiet parts louder.

As you can see, compression literally makes quiet parts of the music louder, and loud parts quiet. By using compression and reducing the dynamic range, you can smooth out the sound by finding a medium between the lowest and highest peak volumes.

Terms to know:
Attack: How fast a compressor will react once the threshold is breached. 0ms will result in immediate action.
Decibles (db): Measure of sound pressure.
Gain: Used to increase or decrease compressed sound. (measured in DB)
Knee: A compressor characteristic that affects the way a compressor behaves.
Milliseconds (ms): Attack and Release times measured by milliseconds.
Ratio: How much a signal is compressed. With a compression ratio of 3:1, a signal which is 9db over the threshold level would be reduced to 3db. A signal of 3db over the threshold would be reduced to 1db.
Release: How fast the compressor will return to its normal state after the signal has moved below the threshold. 0ms will result in immediate return.
Threshold: Threshold level determines which signals are subject to compression. With a threshold of -5db, all signals above this level (-4db ) would be compressed by the set ratio.

Before beginning, you'll need a large decible meter, preferably with a digital readout. As a general rule, your mix before mastering should fall below the 0db mark, and preferably below the -1db spot. Leaving a ceiling will allow you to compress and boost, without having to do too much limiting.

Drums: Perhaps the most important element in a hip-hop track. DJ Premier, Pete Rock, Alchemist, Havoc, RZA, Marley Marl and Timbaland. What do all these producers have in common? Their thumping drums. Now imagine if all those beatmakers made weak drum tracks. Premier's "Come Clean" probably wouldn't be considered a classic, nor would Pete Rock's "T.R.O.Y". Compression is very much needed on drums, especially in the hip-hop world. What exactly does compression do to help? Fatten, thicken, louden, and sharpen. Deep, rumbly kick drums and sharp, snappy snares. Ah, the wonders of compression.
Threshold: -10db to -15db
Ratio: 6:1 to 8:1
Attack: 3ms
Release: 10ms
Knee: Hard
Gain: +5db to +7db---

Percussion: Although not all hip-hop tracks contain, or need percussion, a lot of the newage pioneer beatmakers are using bongos, congas, triangles, steel drums, as well as other percussion instruments. Percussion doesn't require a lot of compression because usually, the percussion track rests behind the drum track. Bongos, congas, and the likes usually have an immediate popping sound that doesn't need compressing, so the attack should be set slower than drums.
Threshold: -3db to -7db
Ratio: 3:1 to 6:1
Attack: 5ms to 7ms
Release: 15ms
Knee: Hard
Gain: +2db to +4db---

Bass: A common problem with bass is that the low notes seem to disappear into the mix while the higher notes stick out like a sore thumb. With many instruments, reverb could solve this problem. However, using reverb on the bass track usually gives it an undesirable effect. By using compression, you can bring up the lows, and submerge the higher notes into the mix. Often times, there is an initial "pluck" to the bass sound, and it can be more beneficial to let this sound slide through uncompressed.
Threshold: -4db to -9db
Ratio: 4:1 to 8:1
Attack: 3ms (if there is a plucking sound, use an attack closer to 7ms)Release: 100ms on short bass sounds / 300ms on long bass tones
Knee: Hard
Gain: +2db to +4db

Brass / Wind instruments: Brass and wind instruments require a "transparent" type compression. Any obvious processing can noticably ruin the sound. Brass and wind instruments have a lot of variety in playing styles. Trumpets can be played expressivly loud, and a smooth, mellow flute will need much different processing.
Threshold: -2db to -4db
Ratio: 6:1 (lighter instruments) to 15:1 (deep brassy instruments)
Attack: 3ms (If a transient sound needs through uncompressed, use 6ms)Release: 300ms
Knee: Hard
Gain: None---

Guitars: When working with acoustic guitars, compressors tend to reveal themselves more so it's a good idea to use a very "transparent" compression. If working with electric guitars, make small increases to the ratio and threshold.
Threshold: -2db to -3db
Ratio: 3:1 to 4:1
Attack: 3ms (If there is an initial pluck, use 5ms)
Release: 30ms to 60ms
Knee: Soft
Gain: 0db to +1db---

Samples: If you're a sampled based producer (specifically, phrase sampler), chances are you don't get to compress several instruments in different ways. Using the following numbers, you'll be able to smooth out the entire sample without too much limiting.Threshold: -2db to -3db (If the sample is recorded bad, and there's lots of peaks, use a higher threshold around -5db)Ratio: 2:1 to 3:1Attack: 2msRelease: 400msKnee: HardGain: +1db to +3db

Full Mix: The final mix doesn't require much compression, although some hip-hop songs have been compressed with a 3:1 ratio, most aren't needed that much. A final compression should act as a limiter, keeping the signal close to the 0db mark.
Threshold: -4db to -7db
Ratio: 1.5:1 to 2.5:1
Attack: 5ms
Release: 200ms to 500ms
Knee: Hard
Gain : Varies---Remember, those are just guidelines. There are no rules to mixing, and no rules to mastering. Hopefully you've learned a few things from reading this. If you're in need of a compressor, there are several software compression tools that you will find handy.
 

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