Compression/Limiting for Dummies

Chris F

Chris F

New member
I'm working with plug-ins for the first time, and have made some good progress with the parametric EQ's at my disposal, and have made a little headway with an e-verb with more controls than I'm ready to understand, but so far am having no luck understanding how the plug-in compression works at all. Every time I try to use it, it just sounds like ASS, and I'm sure that it's because I don't know what the hell I'm doing.

What I'm trying to do is not compress the entire signal, but to simply cut down on some of the volume "spikes" inherent in acoustic jazz, especially as regards piano and archtop guitar. Let's say for the sake of argument that I'm working with a duo recording using acoustic bass and archtop...the bass is a mono signal, centered, and usually doesn't spike if I use a bass rolloff. The guitar is stereo, panned L/R, and has an incredibly wide dynamic range. I love the low end of the dynamic range, but it seems as though the top 6-8 db or so of the range seems to be reserved for about two or three hard "spikes" in each recording, with everything else registering at about -8 db.

How can I use my (Audio Desk) compressor/limiter plug-in to limit these spikes so I can use more of that range for the rest of the music? How should I set the parameters? If anybody has any advice or links to good explanations or compression parameters and their effects - or better yet, advice on how to keep as acoustic a sound as possible while limiting peaks - I'm all ears. So far, everything I've tried ends up sounding like somebody stuffed a wet sock in each of my ears every time the compression kicks in...

Thanks,

Chris Fitzgerald
 
Chris,

> What I'm trying to do is ... simply cut down on some of the volume "spikes" inherent in acoustic jazz <

Then you want to set the compressor so it reduces the volume by only a few dB. and only at the loudest places in the tune. I'd set the compression ratio fairly high - at least 3:1 and 10:1 would be good too. Below is a brief description of compression I posted awhile ago.

--Ethan

===================

A compressor or limiter is an automatic volume control that reduces the volume when the input gets too loud. Originally they were used to prevent AM radio transmitters from distorting if the announcer got too close to the mike. Then some creative folks discovered that a compressor can sound cool as an effect on voices and musical instruments.

The primary controls on a compressor are:

Threshold - also called ceiling - This sets the point at which the automatic volume reduction kicks in. Below that volume the compressor does nothing. When the input gets above that level, the compressor reduces the volume automatically to keep the signal from getting much louder.

Attack time - how quickly the volume is reduced when the input exceeds the threshold. If it's too slow, then a short burst of loud music can get through and possibly cause distortion. So when using a compressor as a tool to prevent overload you generally want a very fast attack time. But when used on an electric bass to get a little more punch, 20-50 milliseconds is often good because that lets a little burst of the attack get through before the volume is reduced. So each note has a little extra "definition" but without the full length of the note being too loud.

Release time - how quickly the volume comes back up after being reduced. If it's too fast, you'll hear the volume as it goes up and down. That sound is called "pumping" or "breathing." Sometimes this sound is desirable, but often it is not. It depends on whether you're using the compressor as a tool to prevent overloading, or as an effect to create a cool sound or add more sustain to an instrument. If you don't want to hear the compressor work, set the release time fairly long (one second or more).

Compression ratio - 1:1 does nothing. 2:1 means if the input rises to 2 dB. above the threshold, the compressor will reduce the level by 1 dB. so now it's 1 dB. above. 10:1 means you have to get 10 dB. above the threshold for the output to go up by 1 dB.
 
Good stuff, Ethan.

Chris, it sounds like you need to discover the joys of the software limiter. Have a look at Waves' L1 or download a demo of this: http://www.sonictimeworks.com/p_masteringcomp.html (it says mastering compressor, but it's really just a limiter).

Since it's just a few random spikes you're worried about, then I'd think a limiter would be all you'd need. You set the limiter's threshold at the loudest volume you want your track to hit. Once the track reaches that volume, the limiter keeps it from going beyond that point (getting any louder), so your spikes are reduced only to as high as you want them to be.

Also, if it's just a few spikes, quit being so lazy ( :) :) :) ), and just highlight the individual peaks in whatever software editor you're using and reduce their volume.
 
Have you applied any bass cut to the guitars? That may do the job better than compression or at least give you a more balanced signal going into the compressor.
 
Thanks for the replies everyone. All of this info will be very useful, especially the explanation of the "release time" function, which I didn't know about before.

CHECKERSTONE,

Unfortunately I can't download anything for my recording setup, because I record on a Mac and surf on my wife's PC. And as for the "lazy" part, I must protest: I'm not lazy, just STUPID (or at least quite ignorant). :D I honestly didn't realize I could do that on Audio Desk... Of course, now that you mention it, it makes perfect sense, and I'll try that. A working limiter would still be nice though.

Thanks again,

Chris
 
CLOISTERMONK said:
Doing that over here too, DURRL? Bad, bad, Chris. ;)
Click to expand...


DOH......busted! :D Like I said before, it's a hard habit to break. Do you suppose they make a patch or special gum for this problem?
 
Ethan,

I just ran the plug in with a short attack time, longer release time, and a 3:1 ratio, and it worked perfectly. Thanks!
 
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