Compression in a Nutshell

Discussion in 'Audio Help & Tips' started by JimMY2NutZ, Jul 4, 2004.

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  1. JimMY2NutZ

    JimMY2NutZ k.matthews

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    Im going to share my knowledge with every body because I always see people asking about it. This is first installment a series that will cover many aspects about compressors, compressing methods, tips, and tricks....

    VOL. 1 - Basic Settings

    One of the first things that you should know is that presets will almost never accomplish what it is you need your compressor to do for the simple fact that you are using a predetermined solution to a unique situation. Every instance you find your self in need of compression will be different then the next, therefore, in order to effectively implement compression into your mix, you must understand what a compressor does, how it does it, and when it should do it. Basically, all compressors do the same thing; they reduce peak levels in an audio signal. And they pretty much all do it in the same way. Every compressor you will every see (analog or digital or plugin or whatever) has the same fundamental settings that will determine how your signal is compressed. Lets start with the threshold and ratio.

    The threshold is the point in decibel that will determine when your compressor will start compressing. When your audio signal breaks this point, your compressor will activate, when it drops below this point it will deactivate. Its really simple to set, usually your compressor will have an input meter that will tell you the level before compression.

    The ratio is the amount in decibel that will be compressed. Its read like this: for every X dbs that exceeds the threshold, the compressor will only let 1 exceed. For example, if you have a signal that exceeds the your threshold by 6 dbs and a ratio of 2:1, your compressor will compress 3 dbs and let 3 dbs go over. If you have a signal that exceeds your threshold by 12 dbs and a ratio of 5:1, then your compressor will compress 9.6 dbs and let only 2.4 go over. As you can see, your ratio and threshold settings work together to determine how much of your signal gets compressed. The higher you set your ratio, the more gain reduction you will get, and the lower you set your threshold, the more gain reductions you will get. So, achieving the appropriate gain reduction will be a sort of balancing act between the two. It should also be noted that you can basically achieve the same result with either a high ratio and high threshold, or a low ratio and lower threshold. For instance, lets say you have a signal that peaks at -6 dbs and has a low at -24 dbs, and you want to reduce the level by 6 dbs. You can do this by setting the threshold at -18 dbs (so that you signal exceeds the threshold by 12 dbs) and a ratio of 2:1 This will cause your compressor to compress to compress 6dbs and let 6dbs go over, thus achieving a 6 db level reduction. You can also achieve the same results with a threshold setting of -12 dbs and a ratio of 6:1. But there are some other things to consider when setting these two settings. For example, since the level reduction occurs across the entire frequency, a kick drum at 75-120 Hz that breaks the compressors threshold to cause a 4 db gain reduction will cause the signal to be reduced across the entire frequency by 4 dbs; that means your snares and strings will also be reduced by 4 dbs. Depending on the amount of compression, this will most likely result in a pumping affect, which will undoubtable ruin your track. Of course there are side chain and multi band compressors that will help you avoid this problem, but lest not get ahead of ourselves....to be continued.....
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  2. Drschmalzy

    Drschmalzy Active Member

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    good...

    maybe they will stop asking about presets and what numbers should I start at...

    Where u set ur threshold also depends on how loud u recorded ur vocals and what not... No preset will work, I should say most of the time, because u are not recording the same way.

    Good thread...
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  3. Xabiton

    Xabiton RM Veteran

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    Good thread I think presets are only good when u make them custom to you but even then id rather just re do it every song so i know everything will be right for that particular situation but then again i dont even really like compression i would rather use velocity and eq but i do use limiting alot
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  4. D-Magic

    D-Magic j-magics bitch

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    good shit here... everyone needs to give dude some rep
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  5. JimMY2NutZ

    JimMY2NutZ k.matthews

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    ....Attack is rather simple to understand and implement; it is the amount in milliseconds that it takes your compressor to start compressing once your signal breaks your threshold. Lower attack times are typical for limiting type applications and when gain reduction is more significant. High attack times are usually used on drums and bass to add punch or character. Its more of a flavor setting that is up to the user to decide what is right for a given situation. But you should consider that the more your compressing, the more apparent your attack setting will be. If your not careful when heavily compressing, a high setting will cause your signal to dip when it actually begins to compress. In addition, you could miss the part of the peak that breaks the threshold; this will cause your compressor to act too late and will likely produce an unnatural sound, similar to a pumping sensation. A low setting can also cause undesired results; depending on what your compressing and how much your compressing, a low setting could produce a flat and boxed in sound. With these things in mind, it usually only takes a couple of minutes to get it right.

    The release setting is probably the most difficult to set, and it could either make or break your compression. It is the time in milliseconds that will determine when your compressor will stop after your signal breaks your threshold, not when your compressor actually begins compressing. For example if your signal breaks the threshold and you have an attack of 10ms and a release of 150ms, your compressor will only compress for 140ms and will stop 150ms after your signal breaks the threshold. The fundamental idea behind the release setting is to have your compressor stop compressing before the next significant/desired break of the threshold. However, you do not want to set your release to low because you will prematurely stop compressing and likely cause a pumping effect. Also, setting it too high will squash your signal because your compressor will not recover in time from the previous threshold break. There are quit a few things to consider when setting the release. In particular, one of the more important things to consider it the tempo the track. Case and point; if you have a rather up tempo track, the signal will break the threshold at a faster pace then it would on a slower track, therefore the release should coincide with the rate at which the signal breaks the threshold; a faster tempo would usually get a quicker release, and a slower track will usually get a longer release. However, the rate can vary throughout an entire track, and cause your compressor to squash parts of your track (like during a justblaze type breakdown, the signal will break the threshold at a faster rate then it otherwise would), This may call for a more crafty approach to the situation, like using automation (more on this later). Another thing to consider is any change in dynamics. Varying dynamics or change ups may cause your signal to break the threshold a different rate. For example your punchy guitar may slow down, change up, or decrease in velocity during a bridge and therefore, require different release settings the during the chorus. (Actually situations like this may require entirely different settings altogether. This will be further discussed later on)...to be continued.....
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  6. Syntax_Mastery

    Syntax_Mastery Emcee/Producer/Engineer

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    good post jimmy
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  7. Hyydro

    Hyydro ah yes yes yall

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    bookmarking this shit; it should also be stickied

    that, and allornothin should be mod already
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  8. JimMY2NutZ

    JimMY2NutZ k.matthews

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    Markup: this setting really need no explanation. Its simply a gain control.

    While all compressors have the same basic settings, some have a few extras. I’ll briefly cover the most common.

    Auto-gain/markup: when this feature is enabled its automatically applys gain to the signal as it is compressed to maintain its max peak level. Usually when this is turned on your signal will become considerably louder as you compress more because your RMS level is increasing even though your peak level is remaining the same. RMS means “root mean squar;” it’s a rough approximation to who loud something seems. While its fair from accurate, its helpful when mixing.

    Some compressors have an automatic release setting. When this is turned on, the compressor will “look ahead” to find the next threshold break and adjust the release setting accordingly. However, please note that these compressors (usually plugins) produce a higher latency and could be ineffective if you do not compensate for it in someway. If your using an application like Cubase, just make sure that plugin latency compensation is turned on. You can manage this from the plugin information menu. Personally, if I have the option, I would always turn this feature on for the simple fact that it makes life so much easier.

    On some compressors, the knee setting is predetermined and cannot be changed, others allow you to adjust it. The knee refers to how a compressor compresses, either instantaneously or gradually. Most plugin compressor you will find have a graph to illustrate the effect of your compression. The x and y axis are your input and output in decibels. The diagonal line is your compression curve, as you set your threshold and ratio, you will see the straight line curve off to the right at the top. The knee setting correspond to how sharp the curve is. With a knee of 0, you will produce a shape angle; as you increase your it, the angel will round off. The idea behind it is to smoothen out the compression so that it sounds more natural.

    A few of the Waves compressors (like the Renaissance Comp or C4) provide you with the option of changing its compression behavior from Opto to Electro. Opto simulates a classic analog model, where the compressor gradually releases the signal. As the gain reduction goes back to zero, the compressor moves slower and slower. Electro behavior is Waves own invention, and simply, it’s the opposite of Opto. Meaning, as the gain reduction goes back to zero, the compressor moves faster and faster. Honestly though, Im not sure if I can hear the difference between the two; maybe I do, but it may just be my ears playing tricks on me.

    the next installment will include detailed info and applications for side chain and multi-band compression (including specifics for Waves C4 and LinMB, graphical multi bands like steinbergs mastering comp, C1 comp-sc, and iZotope Ozone’s Dynamics).
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  9. JimMY2NutZ

    JimMY2NutZ k.matthews

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    the basics for sidechains and multi bands will be up later tonight...
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  10. LiQuiD6

    LiQuiD6 Left hook Justice

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    great post for the noobs...basically everything we are tired of explaining over and over again...


    i must have posted something very similar to this numerous times in the past...lol...

    reputation points indeed
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  11. JimMY2NutZ

    JimMY2NutZ k.matthews

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    its going to go much, much deeper than this though...its just starting of thin to set things up...my next update on it will be getting much deeper into things...
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  12. Phoenix5891

    Phoenix5891 T.S.K.

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    Thanks for taking time out to do this
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  13. JimMY2NutZ

    JimMY2NutZ k.matthews

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    ***I forgot to mention the PDR setting that you can find on the Waves C1 compressors. PDR stands for program dependant release. Its used to compliment your release setting and account for varying durations between threshold breaches, or the transients in your audio signal. For our sake, transients are the short, or quick dynamics in the audio signal. The setting in milliseconds corresponds to the length of the transient. It works like this; any transient that is shorter then the value of your PDR setting will have a shorter release time. For those that are longer, the release will be controlled by your release setting. This setting will help prevent a kick drum or bass from squashing a high hat, or it could help prevent one syllable from squashing an other in a vocal track.

    Now with the basics features and settings covered, we can begin to go deeper into the subject of compression. Before more specific topics like vocal compression, soft-limiting, de-essing, micro dynamics and deep compression, and side chain and multi band applications, I want to cover the basics of side-chain and multi-bands because they are part of the fundamentals. With the availablity of Waves plugins being so high and because of their excellent quality, I will use the C1 comp-sc (side chain) and C4 (multi-band) of my references. While the settings and features will relate specifically to these two, the ideas can be extended to any side chain or multi band compressor (except for the C4's range setting). I will also talk about multi band compressors that use graphical settings like Steinberg’s mastering compressor.

    First, the C1-sc. This compressor is fundamentally the same as the standard C1, with the exception that it incorporates bandwidth filters similar to those found on an EQ. These filters are used to split the frequency into two parts so that compression can be applied to only a portion of the signal. This can be extremely helpful for fixing a mix where the bass is overpowering the whole track; where signal band compression will cause a pumping effects. It can also be used as de-esser or de-popper (more on this these specific applications later). When you look at the C1 comp-sc, you notice that its basically the same as the C1, with the addition of EQ mode and the frequency graph and options at the bottom. Right above the graph, you will see a filter type option with four options: low pass, high pass, band bass and band reject. The low and high pass filters are pretty much the same as what you would find on an EQ. When you select the low pass filter you will see two curves that represent your audio signal in the graph. The red curve represents the part of your signal that will be compressed, and the blue represents the unfiltered part. The band pass filter will compressor only the frequency range that your curve covers. And band reject is the opposite; it will compress everything but the frequency range that you set (you’ll notice that the switching of the color of the curves as you change between band pass and reject). You can monitor what your bands yours compressing by selecting the side chain button under monitor to the right of the graph. The Q setting is does the same thing as it would on an EQ; it changes the slop you your compression curve. Now of course not every side chain compressor will be set up like this, but they all work the same way, so knowing how to use one will go a long way in learning another.

    You can think of multi band compressors as a series of side chain compressors, each with a band pass filter that is applied to one audio signal. Multi band compression is one of those things that are only used when one has to; by no means is it a standard process. One of the more common application is used in mastering to fix a bad mix. For example, it can be used to make some elements, like the vocals, more prominent in the mix. I should note, as I forgot to mention this earlier, all compression should be done on an adequate playback system (this does not mean comp speakers or 200 dollar monitors), especially multi band compression because his type of compression is probably the hardest to implement properly. If at all, it should be use with care and caution; one can easily ruin the track instead of fix it (actually, my advice would be to avoid using it to fix a mix, if there is something wrong with the mix, go back and remix it). Now most multi bands have the same settings as any other compressor, however, you will notice that the Waves C4 does not have a ratio setting. Instead, it has a range setting. It incorporates the ratio and gain control settings, and compression and expansion all into one. It may seem like a lot, but its extremely effective and easy to use. When you set the value to a negative number, it is acting like a compressor. When its set to a positive number, its acting like an expander (more on expanders later). The greater the value in either direction will strengthen its affect....to be continued...I had to cut this part short because I have to go to work, I’ll finish up with the C4 and cover the graphical comps/multis and Ozone’s dynamics next.
    test
  14. Hyydro

    Hyydro ah yes yes yall

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    ive never seen u help anyone out. and ive been perousing this forum for the last 3-4 months.
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  15. veral conflict

    veral conflict beatsrus

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    ^^he has..

    n IMO he has greater knowledge than most of the cats here..

    i member him postin late 03 or real early 04..
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  16. veral conflict

    veral conflict beatsrus

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    aint ridin the cock though.. lol..
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  17. Hyydro

    Hyydro ah yes yes yall

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    oh word, then thats cool..

    i was just wonderin
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  18. JimMY2NutZ

    JimMY2NutZ k.matthews

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    i apologize for not updating this thread, but my comp blew up so ive been offline for a while now, but when it gets fixed i'll update it again, should be within the next week...
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  19. JimMY2NutZ

    JimMY2NutZ k.matthews

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    alright my comp is back up again and i want to continue this thread, and will update it in a day or two but can someone tell me how to post pics here, like where do i upload them for free because i want to add pics to this because it'll make things much more clear in my future posts, especially when i get into compression applications...
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  20. War Machine

    War Machine Sam Antics

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    maybe once the new cats see how much damn shit that is to read, they'll reconsider jus sittin there an movin a few knobs around an learnin how it works themselves
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