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Understanding Compression Dynamics Processors (HW)
Old 10th January 2011
  #91
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Quote:
Originally Posted by MannyTheAvatar View Post
Lets say you've got your ratio set to 4:1 and let's simplify it by not caring about the attack and release and threshold. When the signal hits 4 db above the threshold, instead of getting 4 full db of output (above the threshold) you only get 1 db (above the threshold), correct? OK cool.

So what happens if you only have signal going 2 db above the threshold? Do you get 2 db of output (above the threshold) because you haven't fulfilled the 4 db (above the threshold) requirement for the 4:1 ratio? Or do you get 0.5 db output (above the threshold) because 2:0.5 = 4:1? Or does it depend on the device itself?
??

you get 0.5 dB. 4:1 is a ratio. if the signal goes above the treshold by 0.4 dB, you'll get 0.1dB. nothing extra.
Old 12th January 2011
  #92
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Quote:
Originally Posted by u b k View Post
Not if it's a shelf!





That's true, and in all fairness to the designers of the world, metering is a tricky thing. It's not necessarily there to tell you what's actually going on, in many cases it's there to tell you what it *sounds* like is going on.

The meters on the 2500 are very VU-ish, slow to recover. Paul's a diehard old school engineer, he's used to working a certain way. Distressor/Fatso meters are incredibly accurate at revealing what's actually going on with your signal.

Another thing to throw into the already-heady mix is that some comps distort right at the onset of reduction, so you get some transient clipping that sounds like extra compression but it won't show on the meter. This is actually a huge part of why different comps sound so different, that little nub of distortion at the corner of the knee.


Gregory Scott - ubk
Definitely true on the shelving EQs. I would go as far as to say that if shelves really effected the frequency that was written on the label - it probably wouldn't sound accurate or pleasing. Check the user manual on a Pultec - those shelves extend WAY further than one might expect. Shelf off a little 12k, what do you know, you're still getting reduction at 500Hz.

The way compressors react - built in knee, what the detector is reacting too, the different amp stages and other layers of voltage tansfer creating distortion; it's why compressors also have to be considered for their tonal properties.

When I'm using a compressor on the master buss for example - I'm WAY more concerned about the tone than the actual compressor action. I'm doing the slightest bit of gain reduction generally, with very subtle settings. But the tone.... well, a lot of that tone is there no matter how you set the compressor.
Old 12th January 2011
  #93
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Regarding Greg's assertion about the sound of a compressor before it it even triggers the meters. I remember learning this when I was a teen in NJ. Your meters wouldn't even light up on the comp but you could still adjust the settings on the attack and release, ratio and HEAR IT doing something. Its actually a great way for learning your compressors comings and goings.

I usually think in Dr. Seuss terms for compressors.

Sometimes you want a MWOK VS a ZUMMPA from a compressor on sources.

Peace
Illumination
Old 12th January 2011
  #94
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Stoneface's Avatar
 

Quote:
Originally Posted by illacov View Post

I usually think in Dr. Seuss terms for compressors.

Sometimes you want a MWOK VS a ZUMMPA from a compressor on sources.

Peace
Illumination
heh
Old 14th January 2011
  #95
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Quote:
Originally Posted by pootie2good View Post
amazing video but what are the AC Threshold and DC Threshold for?? he twist them but I can't hear **** until lke 0:23 and it just seems softer than what's the upper button, sound like it would be the make-up gain because now it sound louder but compressed

the time must be the attack button right? it keeps being punchier up to 4, but 5 and 6 I have no idea what I'm hearing
Old 14th January 2011
  #96
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Storyville's Avatar
Quote:
Originally Posted by Simon FP View Post
amazing video but what are the AC Threshold and DC Threshold for?? he twist them but I can't hear **** until lke 0:23 and it just seems softer than what's the upper button, sound like it would be the make-up gain because now it sound louder but compressed

the time must be the attack button right? it keeps being punchier up to 4, but 5 and 6 I have no idea what I'm hearing
With the time setting - it sounds like when it gets up to 5 and 6 - it's just taking such a long time to attack and release you end up getting very little squeeze on the front of the kick, but it's still grabbing the whole of the snare. It makes the shape extremely odd. Big flathead decay on the kicks, and almost linear gain reduction on the snares.

I have no idea what difference between the two thresholds are - but I hear it compress harder (not just more of the signal) when the dc threshold is turned up - kind of like a ratio control.
Old 15th January 2011
  #97
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Quote:
Originally Posted by Storyville View Post
With the time setting - it sounds like when it gets up to 5 and 6 - it's just taking such a long time to attack and release you end up getting very little squeeze on the front of the kick, but it's still grabbing the whole of the snare. It makes the shape extremely odd. Big flathead decay on the kicks, and almost linear gain reduction on the snares.

I have no idea what difference between the two thresholds are - but I hear it compress harder (not just more of the signal) when the dc threshold is turned up - kind of like a ratio control.
On the Fairchild, DC bias is really a knee control, but as the knee is wide open it also affects (decreases) the ratio and lowers the threshold.

Time constants are as such:
1- 200microsec attack, 300ms rel
2- 200microsec attack, 800ms rel
3- 400microsec attack, 2sec rel
4- 800microsec attack, 5sec rel
5- 200microsec sttack, program dependent 2 sec peak, 10 sec multiple peak
6- 400microsec attack, proram dependent 300millisec peak, 10 sec multiple peak, 25 sec constant high input level

paraphrased from UAD 670 manual

I love the Fairchild, don't understand it much, I just know the basics and use my ears with it.
Old 16th January 2011
  #98
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Storyville's Avatar
Quote:
Originally Posted by smoke View Post
On the Fairchild, DC bias is really a knee control, but as the knee is wide open it also affects (decreases) the ratio and lowers the threshold.

Time constants are as such:
1- 200microsec attack, 300ms rel
2- 200microsec attack, 800ms rel
3- 400microsec attack, 2sec rel
4- 800microsec attack, 5sec rel
5- 200microsec sttack, program dependent 2 sec peak, 10 sec multiple peak
6- 400microsec attack, proram dependent 300millisec peak, 10 sec multiple peak, 25 sec constant high input level

paraphrased from UAD 670 manual

I love the Fairchild, don't understand it much, I just know the basics and use my ears with it.
Good info!

Helps to re-iterate the point that hearing what it's doing is what really matters. Cause, sometimes one may not know what the settings do outside of what one hears.
Old 9th March 2011
  #99
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What I am always getting confused about is peak vs RMS compressors. The logic compressor has a peak or rms switch. Both sound dramatically different to each other. and i am always switching between the two. This got me wondering why don't other compressors have this same function and which are they measuring, peaks or rms? I began reading waves manuals to the c4, c6, LMB. To see if they were using peak or rms... I didnt find anything...
Does anyone know if an SSL for example uses peak or RMS?

I have a feeling some people are going to say ya, duh, a peak compressor is a limiter.. but thats not really the case.
Old 14th March 2011
  #100
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u b k's Avatar
 

Peak vs. rms compressor generally refers to what sorts of energy the detector is responding to. Is it responding to the shorter, faster bursts of transient energy, or is it responding more to an average over time? (When I say 'over time', we're talking about extremely small periods of time here).

The current SSL's offer both styles, I don't know about their older designs. I'd have to say the most popular rms-detecting comps out there are the classic dbx's.


Gregory Scott - ubk
Old 15th March 2011
  #101
The dbx 160, 161, 162, 165's?? The black & silver ones. So they are vca rms?
Old 15th March 2011
  #102
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gritzildino's Avatar
 

Quote:
Originally Posted by u b k View Post
Peak vs. rms compressor generally refers to what sorts of energy the detector is responding to. Is it responding to the shorter, faster bursts of transient energy, or is it responding more to an average over time? (When I say 'over time', we're talking about extremely small periods of time here).

The current SSL's offer both styles, I don't know about their older designs. I'd have to say the most popular rms-detecting comps out there are the classic dbx's.


Gregory Scott - ubk
Any Idea as to what the waves plugs use?
Old 20th April 2011
  #103
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Hi guys!
If you would like a deep overview of how compression sounds and examples of different uses, check this out: YouTube - Compression Overview
Old 21st April 2011
  #104
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u b k's Avatar
 

Quote:
Originally Posted by LeoLeoLeo View Post
The dbx 160, 161, 162, 165's?? The black & silver ones. So they are vca rms?

As far as I know, all the 160's are vca, feed forward, and rms-detect.


Gregory Scott - ubk
Old 21st April 2011
  #105
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Quote:
Originally Posted by gritzildino View Post
Any Idea as to what the waves plugs use?

Not a clue, sorry!


Gregory Scott - ubk
Old 29th April 2011
  #106
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Storyville's Avatar
Quote:
Originally Posted by DubMagic View Post
Can Compression Please Be Explained?.

What Is Attack...?
What Is Ratio...?
What Is Gain...?
What Is Threshold...?
What Is Release...?
What Is Knee...?

What Does These Feature's Do?.
This was a question from another thread, but I thought I would answer it here. Sometimes going back to the basics can revitalizes more advanced technique and approach. I also added the knee part.

One of the things that makes compression so "mysterious" or "difficult" is that all the settings influence each other. It's not like an EQ where the you turn a frequency band up or down. It's more like if turning up one band on an eq makes another band's Q get wider - that would make EQing a little more complicated.

In addition, analog circuitry and emulation will give you different tones based on the input, output, and "work" that the compressor is doing. In other words, if the signal comes in 5db hotter, turning the threshold up 5db will not necessarily produce the same results.

However, taking compression one step at a time is a really good way to approach things.

For example, you can start with your tone. This to me is 50% of compression. Tone tone tone tone tone. Run your signal into the front end of the compressor and circle it back in to your DAW/Tape Machine. Put the ratio at 1:1, set the attack to super long (or bypass if available), set the release medium, set the threshold all the way up to 0db. Basically, get the compressor doing the least amount of work possible, so you're just getting a return sound from the actual gain staging of the compressor. Set the level of the signal coming in, and the level of the signal coming out in a way where the TONE sounds best to your ear. This will help you learn your compressor, and will allow you to select different compressors more effectively.

Once you hear the tone you want, then you can select the compression and timing parameters that fit the bill.

For the purpose of this thread, I'm not going to explain what attack, release, threshold, etc. all mean. Plenty of resources that explain these just fine. What I'd like to do is explain the relationship between them.

Threshold is the ultimate control tool. It's going to effect the magnitude of the ratio, the speed of the attack, and the speed of the release. Compression is all relative to the signal that is coming in, and threshold defines that relativity.

The compressor reacts as soon as the voltage surpasses threshold. If the attack is constant, lowering the threshold will effectively make the compressor react sooner, because the threshold is breached quicker. Similarly, the compressor lets go once the signal is ducking the threshold, so with a constant release, the compressor will hold on longer with a lower threshold. Lastly, the ratio will have an overall greater amount of reduction BUT since more of the signal is being effected it actually makes the tonal change more homogenous. You end up hearing less "compression", though the tonal changes coming from the reduction actual touch more of the signal. Kind of confusing, I recommend a little experimentation on that one.

Essentially, threshold is your number one control as it determines just what you are effecting - the attack and transients of your signal? The upper part of the sustain? The deeper part of the sustain? The release? In a sense it's KIND OF like an EQ, you're exaggerating whatever's lurking in certain parts of the signal, except instead of parts of the frequency spectrum you are targeting parts of the temporal band.

The ratio is pretty straight forward. It's basically how hard the compressor is going to work. Really pushing the ratio tends to drive the gain reduction circuit which can have other artifacts outside of the compression. Particularly when the attack and release are very fast. This is why fast, high ratio compression is generally dedicated to a device that is designed specifically for that purpose: A Limiter. But sometimes you want the distortion or pump or breathing that can come from high ratio settings - sometimes it can sound really cool (aka Fairchild). Usually, the way I approach ratio is "as little as necessary to accomplish the task." Most people start at a 4:1 ratio for vocal work, I usually start at 2:1 and move to higher settings if I feel I'm not tucking things in enough - or if I'm getting too much pumping with a lower threshold, I might raise the threshold a bit and raise the ratio as well.

Attack is one of the first places people start getting a little confused, but it's actually pretty simple. Gain reduction has to occur over time. It's unrealistic to have an instantaneous change in voltage - although some compressors can get pretty damn fast. There will be a speed to the gain reduction, and the attack controls how fast or slow the reduction is accomplished. What makes attack confusing is how that idea translates to an actual signal. Basically, the total gain reduction is an idea, -Xdb, but that amount of gain reduction will probably not occur. The sound is probably moving too quickly for total gain reduction to every be met. The attack almost functions like a ratio of the ratio - how much of the gain reduction can be met relative to the shape of the signal that surpasses the threshold. Yikes! A simple affect of attack is how much the initial transient goes untouched. Longer attack settings will ease the amount of gain reduction on the transient of the signal. Part of the transient will always poke through, so you if you are trying to eliminate or soften a transient you really have to set the threshold low and the attack carefully - otherwise you get a "spike" at the attack of the signal.

Knee is the curvature of the attack. All compressors have a knee shape. Some have a "hard" knee where the gain reduction is applied in a linear fashion over time. Others have a "soft" knee, where the gain reduction is milder at first, and stronger as it kicks in a bit more (optical compressors generally have "soft" knees). Knee is just a finer control over the attack of the compressor, one more way to more precisely target the effect you want. Some compressors have a variable knee.

Release is the one that leaves most people in the dark. It's really not much different from the attack. It's how long the compressor takes to ease off of the signal once it's back below the threshold. The effect of the release can be most easily heard on low thresholds - so it's not a bad idea to exaggerate your threshold setting while determining the release time. Release is usually a play between "thickness" and "naturalness." The faster you release, the more of the quiet parts of the signal will be preserved, but too fast of a jump causes notable compression artifacts (many actually distort in a less than pleasing way). Or, you end up getting too much of the lower parts of the signal - so you might get something thick, but perhaps too thick or just too much of something you wouldn't normally hear from the sound. You may lose cut or impact. Too long however, and you end up exaggerating the front end of the signal - the quiet parts are being reduced as well. On low thresholds you can actually hear the compressor letting go and the signal ramps up. This is called "pumping". Then again, this is sometimes desirable. Sounds annoying on things like vocals or a 2-track though.

Here's an example of these ideas working in tandem. Let's say you have an upright bass. It sounds a little dull, and a little soft. You want to bring out the snap of the string, and you want to "thicken" the body of the tone. The string snap is living in the attack of the signal. The tone is the resonance of the basses body which is living at the quieter part of the sustain. You may have bridge sound and fundamental tone living in the decay and upper part of the sustain. You set your threshold pretty low, just above where the release of the bass starts. You set your attack slow, to allow the attack and decay to poke through. You set your release fast, so that the compressor isn't clamping down the resonance of the body. Effectively, what you are doing is reducing the sustain part of the signal. You use the make up gain to return the sustain up to it's original volume, so now you have more attack and decay, and more release - OR more string snap, and more body resonance. You choose a compressor that imparts a nice tone to accent the overtones in the bass signal which also helps give it more presence. You also might choose a compressor that has a rounder knee, to really target just the sustain - perhaps an optical compressor.


That should give some foundational ideas for compression, aside from just basic definitions. Ultimately, you have to hear everything working together to get a feel for compression and how it works. That was really long, so I'll talk about some parallel compression stuff in a later post. I think that was enough for now
Old 29th April 2011
  #107
Some one pay this man!
I'll talk to someone all nite,if possible, but to think out and write this...is a lot of work & thought. All just for you peoples....clapping. Haha!
Old 29th April 2011
  #108
Gear Nut
 

WOW! Great reply. You should write a book!
Old 29th April 2011
  #109
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Great write-up Storyville!
Old 29th April 2011
  #110
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Storyville's Avatar
Quote:
Originally Posted by LeoLeoLeo View Post
Some one pay this man!
I'll talk to someone all nite,if possible, but to think out and write this...is a lot of work & thought. All just for you peoples....clapping. Haha!
Hey man, it's share and share alike. I really appreciate your advice on that mix/production I was working on - helped a lot.

@Overdose - I'm playing with the idea of writing a book. People keep saying I should do it so I'm starting to take them seriously.
Old 30th April 2011
  #111
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Excellent Storyville... You should do YouTube vids... Save yourself from typing a book... heh
Old 30th April 2011
  #112
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Logical Mind's Avatar
 

Storyville for Prez!!
Old 30th April 2011
  #113
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halfguard's Avatar
 

storyville, what are your go to software compressors?
Old 30th April 2011
  #114
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12ax7's Avatar
 

.
I gotta say, Storyville, that the short little ditty that you posted (while I could quibble a bit with it) is one of the most USEFUL overviews of understanding the PRACTICE of using a comp/limiter that I've ever seen!

I've read a whole lotta stuff about compressors, but they usually only explain WHAT a compressor does, where as yours gives a very good example of WHY (and how) you might actually want use one.

I agree with others here that there would be a market for this sort of writing, but it has always been hard to write stuff of this nature:

Because much of the use of dynamic processing involves what is known as "Tacit Knowledge" (and because of the complex relationships between the dynamics of musical instruments and the various parameters of these gain-changing beasts), writing anything actually useful on this subject is not only a bit like a describing an accordion without using your hands, but also a bit like writing a tutorial on "How to Ride a Bicycle".

I think you have a gift for this sort of writing.

.
Old 30th April 2011
  #115
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Storyville's Avatar
Quote:
Originally Posted by 12ax7 View Post
.
I gotta say, Storyville, that the short little ditty that you posted (while I could quibble a bit with it) is one of the most USEFUL overviews of understanding the PRACTICE of using a comp/limiter that I've ever seen!

I've read a whole lotta stuff about compressors, but they usually only explain WHAT a compressor does, where as yours gives a very good example of WHY (and how) you might actually want use one.

I agree with others here that there would be a market for this sort of writing, but it has always been hard to write stuff of this nature:

Because much of the use of dynamic processing involves what is known as "Tacit Knowledge" (and because of the complex relationships between the dynamics of musical instruments and the various parameters of these gain-changing beasts), writing anything actually useful on this subject is not only a bit like a describing an accordion without using your hands, but also a bit like writing a tutorial on "How to Ride a Bicycle".

I think you have a gift for this sort of writing.

.
Quibble away. Open my mind to some new considerations brother. I agree, pretty much all things in this field are tacit knowledge. Which is why nothing I've ever written means a damn thing unless whoever's reading it actually tries my advice on for themselves.

I appreciate the kind words though (I'm a sucker for a compliment).
Old 1st May 2011
  #116
Quote:
Originally Posted by Storyville View Post
1. What is dynamic processing?

A dynamic processor is something that outputs a signal, where the level of the outgoing signal is based on the level of the incoming signal. In other words, a loud signal coming in will come out differently than a quiet signal coming in.

Dynamic processors are sometimes called VCA - or Voltage Controlled Amplifiers - literally meaning that the voltage the unit receives determines the amount of amplification it uses.
Actually VCA is only one type of dynamic processing, it's used on compressors like a DBX 160 or an Aphex Expressor, and many others, there also are optical compressors, like an LA-2a, there are also FET compressors like an 1176 or a Manley Vari-MU and there are Diode compressors like the Neve 33609.
Old 1st May 2011
  #117
Gear Head
 

Thanks storyville for sharing this knowledge, great understanding on this subject! 
Old 1st May 2011
  #118
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12ax7's Avatar
 

Quote:
Originally Posted by Storyville View Post

Quibble away.
[...]
Oh no.

In the context of this thread, that would be more than somewhat counterproductive.

Ever asked for directions, only to have two guys argue over which route to take?

(You just end up more confused than if you hadn't even asked!)

.
Old 1st May 2011
  #119
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Storyville's Avatar
Quote:
Originally Posted by Musiclab View Post
Actually VCA is only one type of dynamic processing, it's used on compressors like a DBX 160 or an Aphex Expressor, and many others, there also are optical compressors, like an LA-2a, there are also FET compressors like an 1176 or a Manley Vari-MU and there are Diode compressors like the Neve 33609.
Ah, I thought VCA was a catch all for dynamic processors.
Old 1st May 2011
  #120
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Storyville's Avatar
Quote:
Originally Posted by 12ax7 View Post
Oh no.

In the context of this thread, that would be more than somewhat counterproductive.

Ever asked for directions, only to have two guys argue over which route to take?

(You just end up more confused than if you hadn't even asked!)

.
Oh - well - start a new thread or shoot me a PM. I'd like to hear your approach. I'm tryin' to get my learn on, shon.
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