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Bass Compression FAQ

This article got rather long, so I've divided it into three sections. This is the Audio Samples article. There are also bass compression explained and bass compressor audio samples.

Q: What is the difference between a Compressor and Limiter?

A: Not much. Think of a limiter as a compressor with a really high ratio (10:1 or higher) and an instantaneous attack. A limiter's primary function is to keep you out of trouble by preventing peaks above a certain threshold (usually preset). 

Q: Some people say compressors should only be used in when recording and never live.

A: Everyone is entitled to their opinion. I disagree. As you can tell from the audio samples, compressors are used to do more than just even out your playing. A compressor can be used as an effect, just like a chorus, flanger, pre-amp simulator, or reverb. Of course, what sounds good in a recorded mix may not sound good live (and vice-versa). If your bass is coming through the front of house mix (PA system), it may already be compressed. You need to be the judge of the sound you want.

Q: Some people say that using proper technique you can do everything that a compressor does.

A: Again, I disagree. With practice and experience you can (and should learn to) control the dynamics of your playing to a very large degree, but controlling the dynamics is just one part of what a compressor does. It can also create sounds that are simply impossible to create by hand. Just check out the audio samples

Q: Some people say you should always use a compressor when playing live.

A: Ignore anybody who gives you musical advice with the word always or never. I use it live as do many other people. Some songs sound better with it, others without it. In some cases  I will even turn it off and on during the same song!

Q: Some people say that compressors ruin the dynamics of the bass.

A: It all depends on what you're after. Sometimes chorus sounds good on a song, sometimes not. Sometimes a bit of distortion sounds good, sometimes not. Compressors are effects and need to be used when the song calls for it. My band covers "White Room" by Cream. On the opening parts with the drums and strings going, I hit the note once for each chord and let it ring. I use the compressor to give me some sustain. After that I turn it off because I play the riffs between the vocal lines more aggressively. A compressor would not let me do that, so in that sense it would ruin the dynamics.

Q: I think I understand how a compressor works, but how does it give my instrument more sustain?

A: Strike a note and let it ring. No matter how hard you hit the note, the peak dies off rather quickly to a certain level for a while and then slowly dies away (sort of like ringing a bell). Let's pretend that the peak (twang!) was -4db, and the ringing note was -16db. Set the ratio to 4:1 and the threshold to -20db. That means when we strike the note the twang is at -16db and the ringing part starts out at -19db. Eventually the note gets quieter, right? But instead of dropping from -16db to -20db, it will drop from -19db to -20db, which is hardly noticeable. 

All we have to do now is add a lot of make-up gain. The whole thing is now louder. When we strike the note hard, it's not nearly as loud in relation the ringing part of the note. And the ringing part of the note seems to die off much more slowly. By the way, do you think anyone's playing technique could do that?

Q: What are those "gain reduction" lights/meters I see on some compressors?

A: They are a visual indication of how much your signal is being compressed. If you see lights indicating -6db, that means your signal is being reduced by 6db. They can be useful for determining how much make-up gain to use. In our case we might add 6db of make-up gain to get the signal to be about as loud as it would be uncompressed.

Q: My compressor doesn't have all of the knobs you describe. How do I know exactly what I'm doing?

A: You don't! Remember, it's the sound that counts, not the numbers. Simple pedal compressors may have just a few knobs, but they usually include one called compression. That's usually the threshold setting - the ratio is preset by the manufacturer. You'll have something to control the level (make-up gain), and the attack. 

Q: How does a compressor relate to an expander or a gate?

A: A gate simply turns off  the gain when the signal drops below a certain level. Or, to say it another way, a gate only allows signals above a certain level to pass through. An expander is a gate that works like a compressor in that instead of turning down the gain completely, it does it by a ratio. You have the same types of settings as you do a compressor (how fast to turn it down, how much, how fast to let the volume get back to normal, etc.). If you're understanding all of this, you're probably thinking a  limiter is to a compressor what a gate is to an expander. And you're right!

Q: What's a multi-band compressor? Or my compressor let's me set at what frequency the compressor should work. What's that all about?

A: Any given note is made up of many frequencies. There's the main frequency plus overtones and undertones that give the note it's tone. An ordinary compressor works on the entire signal. A multi-band compressor is really several compressors in one with each compressor working on a certain band of frequencies. The compressor models that let you set a certain level will compress the only below a certain frequency. I find multi-band compressors only to be useful for an overall mix. The bass compressors with a single frequency setting can be set to operate only signals below a certain frequency and will pass the higher frequencies unaffected. The controls are all the same except for this one additional setting. There's nothing complicated to learn, just experiment and find what you think sounds good. 

Back to the Bass Compressor Settings or back to Bass Compression Samples.

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