Upward expansion vs. compression with gain boost

Discussion in 'Tracking / Mixing / Editing' started by headchem, Nov 9, 2005.

  1. headchem

    headchem Guest

    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?
     
  2. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    the results of the two do sound different. when you use expansion, you are increasing the volume of the louder elements. with compression, you are decreasing the volume of the louder elements.
     
  3. headchem

    headchem Guest

    Did you mean to say "increasing the volume of the quieter elements" for the expander? How the ratio between loud and quiet not end up the same?
     
  4. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    no, with an expander you are increasing the volume of the louder elements.
     
  5. headchem

    headchem Guest

    Ahh, that clarifies things for me. So is this upward expansion used in mastering? Seems like that would make the levels fluxuate out of control, and would lead to clipping problems in the master.
     
  6. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    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.
     
  7. headchem

    headchem Guest

    So this is more of a fix-it for an over-compressed mix, than a technique for making a good mix sound magically better? Upward expansion is used when too much compression was placed on each individual track in mixing. Is this right? Thanks for explaining this for me.
     
  8. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    well you can also use it to get a bit more detail on transients if you tweek it right. it all depends on the program you are working on. if you break it out to a multiband and expand individual freqs, then you have a billion different things you can do.
     
  9. IIRs

    IIRs Well-Known Member

    I really like upward expansion for programmed parts, especially drums: it seems to make them more lively and 3-dimensional, and somehow a bit less fake..
     
  10. headchem

    headchem Guest

    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?
     
  11. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    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.
     
  12. IIRs

    IIRs Well-Known Member

    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..
     
  13. headchem

    headchem Guest

    Just when I thought I understood... What is downward expansion?
     
  14. IIRs

    IIRs Well-Known Member

    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..
     
  15. headchem

    headchem Guest

    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?
     
  16. IIRs

    IIRs Well-Known Member

    I use all 4 in the attempt to do my mixing properly!
     
  17. headchem

    headchem Guest

    So, you prefer these for mixing, instead of mastering? Are any of the "other three" techniques useful for mastering?
     
  18. IIRs

    IIRs Well-Known Member

    No, these are general techniques that should be in any engineers toolbox, like EQ and reverb.. I don't presume to give mastering advice though, as I am not a mastering engineer. :wink:
     
  19. saemskin

    saemskin Active Member

    great thread.
    I've not seen any plugins that offer expansion, aside from the MX5 for powercore and I can never hear it *doing* anything so I never turn it on. Is that because this plugin inherently compresses the signal.
    So, links to some plugs that perform this operation?
     
  20. CharlesDayton

    CharlesDayton Active Member

    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.
     

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