Compression Output Gain

[JKestle]

I'm a little confused on how output gain can affect the compressed signal.

Say you have a transient rich signal with an RMS of -18db(FS) and peaks at -6db.

For the sake of this example, suppose you set a ratio of 4:1 and a threshold of -16db.

Does the increasing the output gain at this stage make the signal push the compressor (threshold) harder? Or has the signal been compressed based on the -18db pre output gain RMS level?

sorry if this sounds confusing, someone please set me straight.

 

[kylen]

Which compressor are you talking about ?

Most of the DAW plugs I use have post-compressor output meaning it is simply an output gain knob following the processing section. Ozone Voxengo and Sonitus compressors behave this way.

Some other ones use the output more in conjunction with a make-up output gain as a type of leveler so that the signal will try to go to the specified output level kind of like an upward compressor or maximizer might. I think PSP MixPressor has a stage that will do that, db-audioware compressor does this too I think with some auto-gain.

As far as "...Or has the signal been compressed based on the -18db pre output gain RMS level?" that depends mostly on which detector algorithm the compressor is using - Peak, RMS, Envelope or some other method of detecting a threshold down the Crest of the wave.

Ozone3 uses Peak or RMS detectors, Voxengo has Peak, Envelope and some other stuff I don't know about I think. Digital compressors also can vary look-ahead time which can give the appearance of responding further down the crest I think just by responding quicker. I don't think this detector stuff is what you're interested in though - you can also work down the crest a bit by opening up the attack considerablly.

I think you're more interested if output gains are discretely seperate from the compression piece or if they are somehow partly integrated forming something of a 'leveling' device - bringing up softer passages automatically to where the output gain is specified as opposed to just bringing up the entire program 3dB for example. Long sentence, eh ?

 

[JKestle]

I think you're more interested if output gains are discretely seperate from the compression piece or if they are somehow partly integrated forming something of a 'leveling' device - bringing up softer passages automatically to where the output gain is specified as opposed to just bringing up the entire program 3dB for example. Long sentence, eh ?

Kylen, thanks for replying.

I don't have a specific compressor in mind for this question, but I'm currently using software for all of my compression needs.

It's a confusing subject for me, but I think you know what I'm trying to get at.

1) Does output/make-up gain affect how hard the threshold is pushed?

OR

2) Does output/make-up gain occur completly separate from the compression action (ratio, threshold, gain reduction)

In situation #1 above, make-up gain would have to be considered when setting ratio and threshold.

In situation #2 above, make-up gain could be left to the end, after ratio and threshold settings were optimized.


It mis my current understanding that situation #2 is true.

 

[kylen]

...I don't have a specific compressor in mind for this question, but I'm currently using software for all of my compression needs...
1) Does output/make-up gain affect how hard the threshold is pushed?

OR

2) Does output/make-up gain occur completly separate from the compression action (ratio, threshold, gain reduction)

In situation #1 above, make-up gain would have to be considered when setting ratio and threshold.

In situation #2 above, make-up gain could be left to the end, after ratio and threshold settings were optimized.


It mis my current understanding that situation #2 is true.

I was trying to say that the answer to #1 and #2 depends on the compressor we're talking about. The the input levels can have the appearance of pushing harder into the compressor (appearing to either lower the threshold or raise the input gain) if there is an auto-makeup gain or 'leveler' stage engaged. Everything depends on the program material being compressed and the compressor used.

For #1 I might try dis-engaging the auto-gain section or leaving it set to 'neutral' till I've set the ratio, threshold, attack & release (if it has those). Once that's done I can push up the auto-gain which will again adjust loudness and density to a certain extent.

For #2 Once the settings are adjusted and the track is compressed to the 'size' that will fit into my mix I'll just bring up the output depending on how loud I want the track...or use the track fader. This is what I usually do as I haven't done much with auto makeup-leveling compressors.

Another thing to think about always, in this case it's because of gain reduction from compression, is that where you're changing the dB level of a track or mix and your monitors play different dB SPL levels for your ears a lower dB or higher dB track may sound very good or very bad until you actually adjust the level back to where it fits in the mix (fletcher-munson) at your optimum monitoring level (maybe 75-85 dBA SPL). This kind of goes along with your feeling that adjustments are a bit interactive anyway - very true !

 

[Massive Master]

Does output/make-up gain affect how hard the threshold is pushed?

OR

2) Does output/make-up gain occur completly separate from the compression action (ratio, threshold, gain reduction).

Output / Make Up gain is ALWAYS post-compression. It has no effect on the threshold (#2 IS correct).

 

[JKestle]

Thanks a lot MM & Kylen.

 

[Farview]

That is there because when you compress something you are always turning the signal down. The output/makeup gain is there to turn it back up, or make up for the lost signal.