daft compression question

If I set the Threshold level in a Compressor to 0db, according to my logic, nothing should happen.  Which, of course, is not the case.  Where have I gone wrong?

I exported a WAV file from Sonar to Sound Forge, and there opened up iZotope Muliband Compressor.  The WAV file was very quiet, max -15db.  I set the threshold in the compressor to 0db on all bands, as a starting point.  I thought that all levels below 0db would be unaffected by the compressor (ie, nothing in the WAV file should be affected).  But, this was not the case. The WAV file did grow significantly, and the new peak was -11db.
The output gain on the compressor was set at 0db.

Don't know about that particular compressor, but if it's a soft knee compressor, it will start compressing (at a lower ratio) well below the threshold.

Do you see gain reduction indicated on its meters?

I was talking about whether the comp's metering was showing any gain reduction.

But it looks like you may be applying 6dB of "makeup gain" to each individual band. Try setting them all to 0dB.

I presume you mean this Gain?   Its set to 6db on each band

Then each band will increase 6dB in volume. This is dependent of the threshold.
 
Threshold is the point where the compressor starts recognizing the signal's amplitude. When the amplitude rises above a certain, it will start to act in a way defined by the attack time, release time and ratio settings. There are 2 ways that the threshold works. It can boost the signal up into the threshold or it can be moved down into the signal. In both the ways, the only part of the audio that gets processed is the part that goes above the threshold.. After the signal goes above the threshold, the VCA turns down the part that is above the threshold, leaving the rest of the signal unaffected
 
So if your gain is up to 6Db, then your signal will be raised

GraceNoteX


I use the the iZotope multi-band compressor.  It has a limiter function as well as the compressor function.  The Limiter raises the volume (depending on where its threshold is set) whether the compressor's threshold is hit or not.

Check where your limiter's threshold is set.  If you need more detailed help, let me know.
Dan

I have the bundled version of this software - have you got the full version (Ozone?)?   The compressor and limiter are seperated.

drewfx1


Make up gain is always applied. It has nothing to do with the threshold. 

The idea is that the compression lowers just the peaks  - i.e. the stuff over the threshold - and the make up gain raises the level of everything, thus the "average level" is increased.

+1

ULTRABRA: "I have the bundled version of this software - have you got the full version (Ozone?)?   The compressor and limiter are seperated. "
 
Yes, I'm using the full Ozone version for mastering, and the full Alloy version for mixing.  I'm using an older version of Sound Forge, so I don't have the bundled iZotope plug-ins.  Would you mind posting a screen shot of the bundled version?  I realize CJay has you pretty well sorted, but I'd like to see what the differences are in the interface for future reference.
 
Thanks.

Hello GracenoteX,  I'm trying to upload a screenshot - not sure its working though ... 

If you can see the image, I'm guessing you might tell me that I have a much less powerful than the full Ozeone version.  I'd be interested to know, as I would consider an upgrade.   If I got Alloy as well it might be overkill, as I have Sound Forge, unless its doing a bunch of different things?  Do you work with Alloy on each Audio track directly in Sonar?