compression question (hey that rhymes)

Discussion in 'Tracking / Mixing / Editing' started by jalipaz, Nov 7, 2001.

  1. jalipaz

    jalipaz Guest

    ok heres the example:
    threshold: 15db
    ratio: 5:1
    so does that mean every 5db the signal goes over 15 it allows 1db? so it would be 16db. right?

    heres another:
    threshold: 10db
    ratio: 3:1
    so every 3db the signal goes over 10 it allows 1db. so it would be 11db. right?

    ok one more:
    threshold: 15db
    ratio: 3:1
    so every 3db the signal goes over 15 it allows 1db. so it would 16db again. right?
    thanx for ur time,
    jal
     
  2. mapostel

    mapostel Guest

    Hi Jal,
    that's about right. It looks as follows:

    Level In | Level out
    example 1

    13 | 13
    14 | 14
    15 | 15
    20 | 16
    25 | 17
    30 | 18

    example 2
    8 | 8
    9 | 9
    10 | 10
    13 | 11
    16 | 12
    19 | 13

    example 3
    13 | 13
    14 | 14
    15 | 15
    18 | 16
    21 | 17
    24 | 18

    PLEASE NOTE: Thresholds in reality are of course usually negative, i.e. the levels would rise like -14, -13, -12... etc.

    Hope this clarifies,

    Matthias
     
  3. jalipaz

    jalipaz Guest

    hey matthias,
    it probably should clarify but it doesnt. im not sure which is ur threshold and what is ur ratio:
    Level In Level out
    example 1 13 13.... is it 1:13 ratio or what i dont get it.
    14 14
    15 15
    20 16
    25 17
    30 18
    can u explain like i did. im sorry if im a lil slow.
    thanx,
    jal
     
  4. mapostel

    mapostel Guest

    hey matthias,
    it probably should clarify but it doesnt. im not sure which is ur threshold and what is ur ratio:
    Level In Level out
    example 1 13 13.... is it 1:13 ratio or what i dont get it.
    Hi Jal,

    Yeah, it's a bit difficult because it's hard to make a proper table with this interface.
    OK, I was referring to your three examples, i.e. taking the threshold and ratio you were mentioning. And all I did was to draw up a table to show how the Out level relates to the increasing in level. you could draw a graph from it and would see how the compression curve flattens above the threshold.
    But your thinking of the first post was right.

    cheers

    Matthias

    BTW: I've edited my post - maybe it makes more sense now... ?
     
  5. jalipaz

    jalipaz Guest

    ok!! thanx!
    jal
     
  6. Jon Atack

    Jon Atack Member

    Hi Jal,

    You are correct. In practice, keep in mind that the attack and release settings will have a big, audible effect on the compression envelope. Use your ears. Happy compressing,

    Jon
     
  7. anonymous

    anonymous Guests

    and one other factor skews the numbers a bit as well - hard knee or soft knee. Your hard knee will give you pretty much the math in the tables, but soft knee will throw a bit of a curve into the numbers that are closest to the actual threshold.
     
  8. jalipaz

    jalipaz Guest

    thanx little dog
     
  9. drumsound

    drumsound Active Member

    Originally posted by jal:
    ok heres the example:
    threshold: 15db
    ratio: 5:1
    so does that mean every 5db the signal goes over 15 it allows 1db? so it would be 16db. right?

    heres another:
    threshold: 10db
    ratio: 3:1
    so every 3db the signal goes over 10 it allows 1db. so it would be 11db. right?

    ok one more:
    threshold: 15db
    ratio: 3:1
    so every 3db the signal goes over 15 it allows 1db. so it would 16db again. right?
    thanx for ur time,
    jal


    Jal,
    By your definitions in your post I don't think you quite understand the relationship of Threshold and Ratio. The way it works is: if the input signal goes over the threshold, its level is reduced (compressed) by the ratio. Audio under the threshold will not be effected. I'm math--phobic so I won't try to give actual numbers, Matthias has done that for you.
     
  10. jalipaz

    jalipaz Guest

    no i did understand that part i was just trying to understand exactly what the ratio does, cause ive heard and read a couple different things. i couldve read them wrong.
    but i just wanted to make sure and now i know.
    thanx guys,
    jal
    anyways isnt it he ear thats always right in this game thats why i love recording soooo much.
     
  11. Ang1970

    Ang1970 Well-Known Member

    Being negative, the dB number represents distance from the zero reference... in other words, when the signal is at -20, it is 20dB lower than 0dB. With that in mind, here is a new way of looking at the table.

    Threshhold -15, Ratio 5:1
    These settings mean that the compressor will pass 1dB for every 5dB above -15 that is fed into it.
    INP=input level
    OUT=output level
    OVER=amount over threshhold
    PASS=amount of signal passed over threshhold
    REDUC=amount of reduction

    • INP | OUT | OVER | PASS | REDUC
    • -20 | -20.0 | 00.0 | 0.0 | -00.0
    • -17 | -17.0 | 00.0 | 0.0 | -00.0
    • -15 | -15.0 | 00.0 | 0.0 | -00.0
    • -12 | -14.4 | 03.0 | 0.6 | -02.6
    • -10 | -14.0 | 05.0 | 1.0 | -04.0
    • -07 | -13.4 | 08.0 | 1.6 | -05.4
    • -05 | -13.0 | 10.0 | 2.0 | -08.0
    • -02 | -12.4 | 13.0 | 2.6 | -10.4
    • -00 | -12.0 | 15.0 | 3.0 | -12.0
    • +01 | -11.8 | 16.0 | 3.2 | -12.8
    • +02 | -11.6 | 17.0 | 3.4 | -13.6
    • +03 | -11.4 | 18.0 | 3.6 | -14.4
    • +05 | -11.0 | 20.0 | 4.0 | -16.0
    When the signal is at -10, it is 5dB above the threshhold of -15. The compressor reduces the gain by 4dB, allowing the output level to be -14, or 1dB above the threshhold of -15.

    Hope that helps.
     
  12. jalipaz

    jalipaz Guest

    thanx that was great.
    jal
     
  13. Jon Atack

    Jon Atack Member

    True. Though, it is indeed possible on many compressors for the threshold to be a positive dB number as well, like jal indicated in his table.

    Jon
     
  14. Ang1970

    Ang1970 Well-Known Member

    Yes, I could have kept the table going into positive input values... I'll work on it in a bit... :)

    Threshhold +5, Ratio 5:1
    These settings mean that the compressor will pass 1dB for every 5dB above +5dB that is fed into it.
    INP=input level
    OUT=output level
    OVER=amount over threshhold
    PASS=amount of signal passed over threshhold
    REDUC=amount of reduction

    • INP | OUT | OVER | PASS | REDUC
    • -20 | -20.0 | 00.0 | 0.0 | -00.0
    • -15 | -15.0 | 00.0 | 0.0 | -00.0
    • -10 | -10.0 | 00.0 | 0.0 | -00.0
    • -05 | -05.0 | 00.0 | 0.0 | -00.0
    • -00 | -00.0 | 00.0 | 0.0 | -00.0
    • +05 | +05.0 | 00.0 | 0.0 | -00.0
    • +06 | +05.2 | 01.0 | 0.2 | -00.8
    • +08 | +05.6 | 03.0 | 0.6 | -02.4
    • +10 | +06.0 | 05.0 | 1.0 | -04.0
    • +12 | +06.4 | 07.0 | 1.4 | -05.6
    • +15 | +07.0 | 10.0 | 2.0 | -08.0
    • +18 | +07.6 | 13.0 | 2.6 | -10.4
    • +22 | +08.4 | 17.0 | 3.4 | -13.6
     
  15. anonymous

    anonymous Guests

    All perfectly clear, unless you venture into the alternate universe of Joe Meek compressors - in which case none of this will have any meaning at all. Anyone offering a "Meek as a 2nd Language" course? :eek:
     
  16. Jon Atack

    Jon Atack Member

  17. Jason Poff

    Jason Poff Guest

    The threshold is a set value. To lower the threshold you raise the input.

    Jason
     

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