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It seems to me that upward expansion will yeild the exact same results as compression with a gain boost. Either way, the ratio between loud and quiet parts of the mix will end up the same, right? If I am wrong, can someone please explain the difference between these two?

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Michael Fossenkemper Wed, 11/09/2005 - 06:30

It's used a lot in mastering. if I'm mastering something that has been a bit too compressed, i'll use some expansion to reverse the effects of being over compressed. as far as clipping, just turn down the output of the expander and you shouldn't have a problem. If you use it tastefully, the levels won't seem out of control, it'll just sound more dynamic.

anonymous Wed, 11/09/2005 - 07:06

I use Reason 3.0, and it doesn't have a built-in upward expander, but I'm going to start thinking about how one could be constructed in it. So you have to trade off overall volume when using an uncompressor then? Also, so using an upward expander in conjuction with a compressor would cancel each other out when mastering, right?

Michael Fossenkemper Wed, 11/09/2005 - 07:38

they would only "cancel each other out" if they had the exact same settings as far as attack, release, and ratio and you were using the same unit for both. don't think in simple general terms about compression and expansion. these are very powerful tools that have many complex variables that you can tweek to sculpt sound. The more complex the compressor, the more variables. change one value on one setting and you change the behavior of the unit. now add in an expander and there are more variables than you can shake a stick at.

IIRs Wed, 11/09/2005 - 08:23

They only "cancel out" in the sense that compression reduces your dynamic range, while expansion increases it. Otherwise they sound very different, and upward expansion is rarely capable of rescuing material that has been over-compressed.

Personally I use upward or downward expansion settings just as often as I use conventional compression..

IIRs Wed, 11/09/2005 - 09:39

There are 4 basic types of dynamics processor: the conventional compressor is a "downwards compressor" ie: when the threshold is exceeded, the gain is reduced.

"Upwards compression" increases the gain whenever the signal is below the threshold. (I suspect this is actually what you meant by "upward expansion" in your first post!)

Likewise, "upward expansion" increases the gain when the signal exceeds the threshold, and "downward expansion" reduces the gain when the signal is below the threshold.

All 4 types have their uses, even though many (most?) people are only aware of the first..

anonymous Wed, 11/09/2005 - 11:51

You're right, IIRs, I did confuse upward compression for upward expansion. Thanks for the simple summary of all 4 types. I woke up this morning only aware of the first "downward compressor." Time to remaster everything / invent ways to do the other 3 types of compression within Reason 3.0... In the end, though, if I've done my mixing correctly, should I have any use for any of the 4 companding types in the mastering stage?

CharlesDayton Thu, 11/10/2005 - 09:27

I use downward expansion to deal with dialogue tracks that were recorded in reverberant spaces. It cuts down on the reflections. Here is what I always wondered; what is the difference between gating and downward expansion. I'll hazard ny own guess. Gating is a strict cutoff below a certain threshold, expansion works more like a compressor, gradually lowering material below the threshold. Let me know if I'm wrong.