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Understanding Compression Dynamics Processors (HW)
Old 1st May 2011
  #121
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Storyville's Avatar
Quote:
Originally Posted by halfguard View Post
storyville, what are your go to software compressors?
Rvox for a round sound with a polished low-mid range. It either works immediately or doesn't.

RComp for precision - super versatile.

UAD LA2A, and Neve33609 - Good tone monsters - again usually work or don't work fairly quickly.

API2500 - That's my favorite. Gives you tons of control over the whole gammet - if I can't get it sounding right with this one, something else is wrong.
Old 1st May 2011
  #122
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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!
The bummer is reading back on it, I feel like I totally overgeneralized. Tacit knowledge man - can't really put it into words. But yeah, you can tell by how much write that I can talk about this stuff for days. Let's face it, (not so) deep down - we're all a bunch of nerds when it comes to this stuff. Hahahahaha.
Old 1st May 2011
  #123
Long story short: there is no Vulcan mind meld.

And I generalize on purpose. I'll plant a seed, won't give a tree. It's impossible. And if could, the branches would get broken on the way back to their home and there would be no root foundation so the tree would only live a few days.
Old 1st May 2011
  #124
Quote:
Originally Posted by Storyville View Post
Ah, I thought VCA was a catch all for dynamic processors.
no a vca based compressor is one type of compressor, Opto is another, so is a FET so is a Diode, they behave differently and sound differently. A DBX 160 for instance, sounds and behaves differently than an LA-3a or an LA4. So do fet and diode compressors. For instance the standard wisdom is opto's are great
for vocals and bass, but not so much for say drums or 2 buss. You rarely see opto's that very parametric whereas many vca based units are VERY parametric.
Old 2nd May 2011
  #125
Quote:
Originally Posted by Musiclab View Post
no a vca based compressor is one type of compressor, Opto is another, so is a FET so is a Diode, they behave differently and sound differently.
Total noob elec guy & designer disclaimer: insert here... Haha.

But a fet is a field effect transistor which controls flow by dropping or lacking voltage of signal.

A VCA is a voltage control amplifer which controls flow on amount of voltage applied.

Opto circuit is amount gained ot attn'ed is light sensitive.

A diode is to insure a flow goes one way. How does it control the flow variably?
Old 2nd May 2011
  #126
Quote:
Originally Posted by LeoLeoLeo View Post
Total noob elec guy & designer disclaimer: insert here... Haha.

But a fet is a field effect transistor which controls flow by dropping or lacking voltage of signal.

A VCA is a voltage control amplifer which controls flow on amount of voltage applied.

Opto circuit is amount gained ot attn'ed is light sensitive.

A diode is to insure a flow goes one way. How does it control the flow variably?
Honestly that I don't know. I'm not a designer, just a guy who's been using this stuff for a pretty long time now.
Old 2nd May 2011
  #127
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u b k's Avatar
 

Quote:
Originally Posted by LeoLeoLeo View Post
A diode is to insure a flow goes one way.

Very often true, but not always. A diode is also used to stop flow altogether unless and until a specific voltage is reached, at which point it lets everything thru. Diodes can regulate voltage as well, only allowing a specific amount of voltage thru regardless of how much is applied (up to a point).

Zener diodes will pass a reverse voltage up to its breakover voltage, at which point it will regulate the voltage and limit it to its breakover rating.


Quote:
Originally Posted by LeoLeoLeo View Post
How does it control the flow variably?

In every circuit that I know of (which is, to be sure, a small and incomplete subset) there are at least two diodes, either in series or in parallel, preceded by a series resistor, or in some other kind of bridging configuration.

The basic idea in a diode limiter, as understood by my feeble but growing brain, is that you exploit the forward and reverse voltage behavior of diodes in series such that the maximum voltage of an ac current (i.e., audio signal) passes unchanged until it hits a specific level, call it A, then it hard clips until voltage drops below A, at which point voltage passes unmolested. If you lower the voltage fed to this diode bridge, you effectively 'raise the threshold' as more signal is allowed to pass without clipping. Conversely, driving into the bridge harder means more clipping.

If the real geniuses at this stuff, like Wade at Chandler or Paul at Tonelux, hung around here they'd explain it better and no doubt correct some of my thinking. I expect if you asked over at geekslutz or prodigy they'll feed you all you can handle and then some. thumbsup


Gregory Scott - ubk
Old 2nd May 2011
  #128
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Storyville's Avatar
Quote:
Originally Posted by Musiclab View Post
no a vca based compressor is one type of compressor, Opto is another, so is a FET so is a Diode, they behave differently and sound differently. A DBX 160 for instance, sounds and behaves differently than an LA-3a or an LA4. So do fet and diode compressors. For instance the standard wisdom is opto's are great
for vocals and bass, but not so much for say drums or 2 buss. You rarely see opto's that very parametric whereas many vca based units are VERY parametric.
Cool. I've edited the post. Thanks for clarifying.
Old 2nd May 2011
  #129
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u b k's Avatar
 

Quote:
Originally Posted by Musiclab View Post
For instance the standard wisdom is opto's are great for vocals and bass, but not so much for say drums or 2 buss.

Which is why it's extremely important in life to question the accepted wisdoms of the day.


Gregory Scott - ubk
Old 2nd May 2011
  #130
Quote:
Originally Posted by u b k View Post
Which is why it's extremely important in life to question the accepted wisdoms of the day.


Gregory Scott - ubk
Well sure unless you need that opto for the lead Vocal. For me compressors on drums are all about being fast, and by that I don't mean fast attack, there are some compressors that will absolutely suck the like out of a drum no matter where you set the ratio/ attack and release
Old 3rd May 2011
  #131
Gear Maniac
 

This overview of the relationship of compressor settings by storyville was very great and very helpful.
I found another video on youtube that actually shows the different applications for a compressor. It pretty much illustrates more or less what storyville was sharing.

YouTube - Compression Overview
Old 27th July 2011
  #133
Gear Addict
 

Storyville, could you write something about what type of compressor or features one would want for particular recording applications? Meaning what are people aiming for with certain compressors recording vocals, versus drums, versus acoustic guitar, etc? And some info on what instruments tend to need the use of compressors and why would be great to add to this already great thread of yours. I know for example people new to compressors might understand compression can be a big part of recording drums but then ask questions like the role, if any, of compressors for electronic music, synths. Etc.
Old 27th July 2011
  #134
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Gatsby here. I was told the article written by someone in another thread and forum about compression that I pasted here for a short while was technically inaccurate, so it's been deleted. I'm looking into whether the helpful pictures in that article are accurate enough to repost down below because they might be helpful for more visual-minded people trying to learn about compression.

Last edited by 121840; 29th July 2011 at 10:09 PM.. Reason: Technical Inaccuracies
Old 27th July 2011
  #135
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Here are links to further articles. Many contain redundant info to what has already been presented here, but it's always good to reread stuff. And you can copy and paste these articles into documents to print if you want to keep the info handy. They're all articles from Sound On Sound magazine.

Compressors Exploration - Compressors

Compression Made Easy -
Compression Made Easy

Compression & Limiting Exploration -
Compression & Limiting

Advanced Compression Techniques Part 1
Advanced Compression Techniques, Part 1

Advanced Compression Techniques Part 2
Advanced Compression Techniques, Part 2

How And When To Use Mix Compression
How & When To Use Mix Compression

Practical Multi-Band Compression
MULTI-BAND WORKSHOP
Old 28th July 2011
  #136
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CHI CITY PIMPIN's Avatar
 

Gatsby, no homo but I love you
Old 28th July 2011
  #137
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u b k's Avatar
 

Quote:
Originally Posted by Gatsby View Post
Here is another thread turned article from a guy known as "endquoth," so thanks to him. This is redundant a bit, and I don't know if it's perfectly technically correct through and through...

There are a lot of technically incorrect assertions and definitions in there. Commonly held misunderstandings, to be fair, but wrong nonetheless.

His definition of attack and release are wrong, as is his understanding of what happens to the signal both above and below the threshold, as is his description of a limiter, and a good deal of his explanations that then flow from those misconceptions are likewise wrong.

Welcome to the internet!

Honestly, you'd be doing the world of 'good information' a favor if you deleted the post.


Gregory Scott - ubk
Old 28th July 2011
  #138
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MotifStudios's Avatar
 

That is an epic post Story. Nice and very imformative thanks.
Old 19th August 2011
  #139
Gear Maniac
 

This HD video (in sound) definitely shows the benefits of "finger riding" versus a compressor:

HPJ Video - PUREMIX

Make sure you re listening to it in on good speakers/headphones that are accurate with respect to transients.
Old 20th November 2011
  #140
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Quote:
Originally Posted by Storyville View Post
I'm going to throw this up as I think it will be a helpful post. It's not totally comprehensive, but it's a good start.

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.

2. What are the basic types of Dynamic Processors?

Compressors - the most common - the louder the signal is coming in, the less level it provides going out. In a compressor, a target level is set - called the "threshold" - and any signal coming in that exceeds that level will be reduced. The higher the level is above the threshold, the more reduction is done. More on this later.

Expanders - the quieter the signal is coming in, the less level it provides going out. In other words - it makes quiet signals even quieter. Much like a compressor, the threshold is set at a certain level. Any signal that does NOT exceed that threshold is reduced, and the quieter the signal, the more reduction is done.

Limiters - limiters are like super compressors. The idea is to ensure that the level does not exceed the threshold. Because this amount of compression is extreme, a limiter relies on certain functions and design that regular compressors do not have.

Gates - gates are like super expanders. Anything that does not exceed the threshold is reduced to inaudible. Again, because gates are extreme, they often require a slightly different design than a regular expander.



Now - I'll focus primarily on Compression, because that's going to be the most commonly used dynamic processor.

----------------------------------------------------

COMPRESSION

Every signal you hear is compressed. ????? Yes, every signal you hear is compressed.

Bare with me. Imagine you have a rapper in front of a microphone. The rapper raps, you record. You play it back. You haven't used any processing - you're just playing back the raw vocals.

You are listening to a signal that has gone through at bare minimum 3 stages of compression - and more likely than not - it's closer to 6.

The microphone capsule gains tension as the rappers voice pushes it - in other words - it pushes back - and the more the rapper's voice pushes in - the harder the capsule diaphragm pushes back. In other words, the louder the signal hitting the capsule, the more reduction the capsule does to the signal. That's compression! (It's mild compression, but it's still compression).

Along the way through the microphone, you may hit a tube. Tubes have a non-linear response to voltage - the response is quite curved, and also changes the frequency balance of the signal. This is called saturation - which will tend to "round out" a signal, by reducing the loudest peaks. Compression! And before leaving the microphone, the signal may hit a transformer as well, which will saturate in a similar way. (more compression).

The preamp is going to have multiple stages of saturation - and often times, the more gain you give something - the deeper that saturation curve goes. In other words, the more you drive the signal at the preamp, the more compression the signal experiences.

Then the sound has to actual come out the speaker cones. Well, those speaker cones are going to build up tension when pushed further. See where this is going? This is called "cone compression".


Ok - so this is a bit of a simplification - but there's a point here. The point is that "compression" is always part of the signal. Some mics have less of it, some have more - same with speakers, tubes, transformers, etc. And they all do it in different ways. With tubes, people will talk about their saturation curves and THD (total harmonic distortion - or frequency alterations). With mics people will refer to how it "grabs" a sound - or more specifically - the sound's shape. These all add up to really the most important ideas:

Frequency and Shape!

Instead of thinking of a compressor that compresses - think of it as something that changes the shape of a sound. If you start listening for "shape" the mysteries of compression will reveal themselves to you, and fairly quickly.

Setting a compressor is like setting a mold for the signal to fit into. The threshold determines where the compressor starts working, the ratio is how hard it's going to work, the attack is another way of saying how sharp will the transient sound be, and the release is how much tail or sustain do you want to emphasize.

Yikes! Time out!

What the hell is a transient? A transient is a very fast signal - in other words the "attack" of the signal. Drums have transient attacks. Strings have gradually risinng attacks. So the attack control on the compressor is really like saying - how much emphasis on the attack of the signal do you want? Do you want the attack to be really rounded out and diminished? Set the attack low. Do you want the attack to be prominent and stick out? Set the attack high. Of course, this works directly in conjunction with the threshold. Try it yourself, set the threshold low, and the attack short. Suddenly, the attack sound of your snare is gone. Set the threshold low and the attack long. Suddenly the punch of your kick is very round and bouncy. Set the threshold high and the attack short. Now the snare is a little fatter and rounder, and not quite as s***** (but possibly a little duller). Set the threshold high and the attack long - the change is hardly noticeable, the attack is just a little bit "rounder."

How to achieve maximum punch?

There is a thin line between a transient sound, and a sustained sound. A sound that holds for any noticeable amount of time is sustaining. A sound that moves by too quickly to register as it's own moment is transient. But transients can vary in length. A transient can be half a millisecond. It could also be ten milliseconds. And those won't sound the same. A big factor in punch is how long that transient exists. A quick transient sounds "s*****" - but a long transient sounds "punchy." You want to find the point that makes the transeint exist as long as possible before "flattening out" or becoming a sustained sound. Only your ear can tell you where that point is.

Good samples are already shaped to have that kind of impact - and any additional compression may soften that. Of course, punch has a lot to do with frequency as well - but that's for another thread.

Now what about the release? The release is super elusive. It deermines how long it takes for the compressor to let go. If the release is too short for the signal you are going to get a disjointed sound shape which usually results in distortion. If it's too long, your signal never really returns to its natural shape, and you generally lose tone. So the idea is to find a point that emphasizes the sustain (which is where most of the signals tone lives) properly.

Lastly, when the attack and release are set in a way that seem to argue - the compression can become very audible. You either hear the decent or the acent of the signal level. This is called pumping. It's generally annoying, but can sometimes be used an effect.

----------------------------------

So, rather than think of a compressor as something that effects the "level" of a signal. Think of it as something that effects shape. Why? Because level can be controlled with the volume fader more accurately and transparently. A fader doesn't really control shape, unless you are being extremely meticulous. Conversely, compression will always effect the shape of the sound it is working on.

Once you start hearing shape, you will understand compression.
most people would not consider a linear gain change as compression.

compression is generally a non linear function that squishes down the top of a signal when it gets too big.

some compressors will squish up the bottom of a signal.

and a few will squish top and bottom while maintaining the same rms.

a linear gain delta would linearly change the top and bottom to be closer together but the rms would become lower.
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