Compression?

a compressor will squash loud notes and bring up softer ones, so it makes your playing seem more even. nice if you are slapping and playing with your fingers... It can also alter your tone slightly and make it seem more punchy depending how much compression you use and the attack and release settings

 

there's been plenty of threads about this recently - for more descriptions you could try searching.

Be careful with that description, because it's technically not accurate.

A compressor squashes loud notes. That's all it does. However, it allows you to (once the loud notes are squashed) increase the overall gain before peaking occurs. So, the impression it gives is that it's evening out the loud and soft notes, but all it does is soften the loud notes to bring them more in line with the soft notes.

Compressors are used in many different ways, so to describe the effect on a signal is like trying to describe every fish in the sea in one sentence. Suffice to say that most bass players use them to enhance the punch (or attack) of notes by having a comparatively slow attack time. This means that the loud notes are still loud for the first few milliseconds - then the compressor kicks in and brings them down to the "nominal" level.

 

really!? I thought you got more punch by using faster attack settings (I don't know why?), but what you said actually makes more sense!

could you maybe give some more simple suggestions of what sounds different attack and release combinations will give?

thanx

 

sorry dude, been away for a week and have only just gotten back to the forum.

You just gotta think about it logically really.

fast attack means the compressor kicks in quickly. I guess it's a common misconception to think that a higher attack results in more punch... and I'm sure some manufacturers do it this way (especially for bass specific compressors.)

However, it's all relative; a slower attack doesn't always mean more punch. Too slow and the compressor never kicks in and you may as well have it bypassed. So, a short attack is no good, a moderately long attack is where it's at, too long is useless. Vary this control whilst picking a note and you'll hear an awful pinched attack at low settings, a punchy attack at mid settings and no effect at high settings.

Again, it's all relative because if the release setting is set wrong you won't hear the difference in attack settings! For max punch, fast release times are needed. But, fast release tends to reduce the "compressed" sound that is sought after by many Tony Levin freaks (including myself) so again, moderation is required. Compromise is the name of the game.

Long release times are good for sustain - but again it has to be done relative to the other settings or you'll hear no effect or what's called "breathing" where you can hear the compressor working - which is no good.

All important obviously is the threshold and ratio settings, which govern the whole kit and kaboodle. Then, the output level allows you to compensate for the perceived volume loss by matching the bypassed volume with the compressed volume. Don't make the mistake of setting this at unity and then dialing in compression because you'll loose volume hand over fist.

It's kinda hard to put it all in words, but if you spend some time futzing and thinking it through you'll get the idea.

I set mine with moderate to slowish attack, a fairly fast release (maybe 0.5-1 second), and ratio to max. Then, set the threshold so that the compressor is squeezing by about 3-6dB (or about 3 or 4 LED segments if you have them!) Then, compare bypassed with compressed, set the output level so they're perceived to be the same volume and bob's me uncle!

 

Compression basics:

[font=&quot]Compression has 3 basic uses (the first two are very similar), from what I have seen:

1) Speaker protection
2) Signal leveling
3) "Squash" effect

All of this is accomplished through the basic function of a compressor- gain reduction. This is how they compress the dynamic range. Some compressors have an adjustable amplifier on the output that provides "make up gain". This is why some folks think that a compressor makes a signal louder. The amplifier made the signal louder… period.

You usually have a few controls on a compressor:

Ratio: the amount of reduction applied for a given increase in signal. The higher the ratio the higher the reduction. 1:1 equals no compression. 3:1 means that you get 1/3 of the actual increase in signal strength. Infinity means that no matter how big the input signal gets, the output signal gets no larger.

Threshold: What point the compression actually starts happening. If you set the threshold low the compressor starts working quickly. If you set it low with a high ratio you will get a very steady output (though low) no matter what the input signal is. This is how you get a super-squashed sound.

Knee: Hard Knee is where the compression comes on very quickly near the threshold. Soft Knee is where the compression come son in a gradual manner. Most soft-knee settings actually start compressing before the threshold setting.

Also, some compressors have a display for gain reduction, and sometimes it is a multimode display that can show other parameters. I really like to have an indication of the amount of gain reduction being applied. It makes it easier to set the compressor correctly.

In Use:

The least audible use is a soft knee with the threshold set high and the ratio set low. This will keep the big peaks down and leave most of the dynamic range intact. The actual setting for your application will be a function of the input signal level, the range of the input signal, and the output device sensitivity. Again, when you set the threshold the threshold is fixed at that setting, so the sound of the compressor changes with changes in input level.

For Example:
Using volts instead of dB, for clarity, say you set the threshold at 1.5V and the ratio at 4:1. As you approach 1.5V the gain reduction starts, and as you go from 1.5 to 1.9 the output level actually goes only to 1.6 (because 1/4 of the 0.4V increase was allowed). If you have a level that swings from 0.5 to 1.8V you will only get compression at the peaks with a range of 0.5 to ~1.6V. If you engage an effect that boosts the range to 1.0 to 2.3V your range is slashed to 1.0 to ~1.7V, and you hear compression earlier. You didn't change any settings but the compressor will be more of a factor in the final sound.



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