how to raise signal that are under threshold with a compressor?

[kenoir]

Hello:

Could someone kindly help me with this question, I know a compressor works in this way as people told me, but how is this done?

I'm experimenting with a Behringer MDX1600

Can expand and compression be done with the same channel of a compressor? Or does it take 2 channels?

Will the low volume vocal murmur and drum strokes benefit from this process in a live and recording session?

Thanks and looking foward to the reply.

Ken

[noisewreck]

You can't raise a signal that's under the threshold set in a compressor. Compressor "compresses" i.e. lowers the volume of a signal that is over the threshold. Once you've lowered the louder parts of the signal, then you can raise the entire signal using make-up gain.

You can both expand and compress on the same channel, but it will take two devices patched in series to accomplish that.

[SouthSIDE Glen]

Most standard compressors provide only downward compression like Noisewreck explains, but there are a very few compressors and plug-ins that will do what you're looking for and provide upward compression (i.e. compressing signals below the threshold up towards the threshold.) My favorite and one that I highly recommend as a compression tool in general is a software plugin called Dynamizer from Roger Nichols Digital. A very flexible and powerful tool that'll compress and expand in both directions, and in fact - contrary to the comventional wisdom - will let you expand and compress simultanously on a single channel.

It's a bit confounding and a bit of a curve to those habituated only in downawrd-only compression, but for those whose minds are not yet in that rut, or who grew up (like me) learning about expansion and compression circuits for noise reduction long before they ever saw a studio compressor, it's a pretty natural and logically-set up tool.

Also, just to avoid some misunderstanding; upward compression and expansion are not the same thing. What you ask in the title, raising signals under the threshold up toward the threshold, is upward compression. The expansion you mention in the body of your post means pushing levels away from the threshold. Not the same thing at all. But don't worry, the Dynamizer can do any of it, and do in up to 4 different volume "zones" simultaneously, all on one channel.

G.