compressor question about effect below threshold.

[crabtwins]

Hey im pretty new here so thanks for reading. I am slowly getting my way around actually being able to understand the details of compression and there are a few light bulbs that havent turned on for me yet.

1. The threshold is the level at which compression is supposed to start. So then why do I see some gain reduction meter jumping (albeit small) for a signal that is below threshold. I have heard that compression squashes the loud and lifts the low, but I thought the lifting of the low was a perception effect of squashing the loud?

2. Any ideas on understanding (mathematically) the link between release and attack? For instance I know that t=1/f does knowing that help me understand the setting of release and attack for a certain sound, for instance bass?

3. Does release time begin when attack starts or is it measured from when the threshold is hit?
that's it for now thanks

 

[tarnationsauce2]

1. The threshold is the level at which compression is supposed to start. So then why do I see some gain reduction meter jumping (albeit small) for a signal that is below threshold. I have heard that compression squashes the loud and lifts the low, but I thought the lifting of the low was a perception effect of squashing the loud?

Probably because you have a soft knee set on the compressor. That makes the threshold more rounded and gradual.

2. Any ideas on understanding (mathematically) the link between release and attack? For instance I know that t=1/f does knowing that help me understand the setting of release and attack for a certain sound, for instance bass?

If your bass is popping w/ finger strokes, will want to decrease the attack time to squash the pops. But if you want percussiveness, then a longer attack will allow thepeaks to get through.
The release I usually leave somewhat long for bass.
Depending on what you are putting the compression on really matters. You have to explore really. There is no hard-set math way of doing it (such as with tempo). But you can put it into consiteration.

3. Does release time begin when attack starts or is it measured from when the threshold is hit?

When threshold is crossed.

 

[crabtwins]

thanks tarnation

 

[RDMSstudio]

Quick guide to compressor setting

<Threshold> determines how much impact the compressor has on your sound.

<Attack> determines how long before the compressor kicks in so to speak. So think of it in terms of the higher the setting the edgier and more natural the sound. 4ms is a typical control setting wheras around 12-18ms is used in applications that require more original sound to get through.

<Release> determines how long before the compressor lets the sound return to it's original level. Long release times help even out a sound (400-600ms), short release times give more of a controlled edge (50-300ms).

<Ratio> determines the degree of compression. So if there is a 10dB signal over the threshold, a 2:1 ratio will reduce this to a 5dB over.

As a quick guide to setting a compressor...........

- Set your ratio to Infinty:1. Attack to 0 and your Release to 5ms. The Threshold is set low enough to impact the sound (typically around -25dB).

- Play back your sound and slowly bring the attack up till you get the front end of the sound as you want it. The overall sound will be bad due to the fast release but we are only focusing on the leading edge. As you come up from zero attack you will hear a more defined sound, typically around 3-6ms for an individual track.

- With the attack set now bring the release up to around 700ms, then slowly reduce it until there is a musicality to what your hearing. Always use the highest release time you can unless you are producing a specific effect.
Musicality is an individual intepritation but what you should be looking for is a release that makes your sound come alive. (The ratio will still be squashing the sound but just focus on how the sound breathes).

- Reducing the ratio will now determine how deep the compression is. The setting for this is entirely subjective but usually is a balance between the control required and the clarity you need.

- Reduce the threshold till the effect you have created JUST dissapears. Then bring it back up again till it just reappears....NOW LEAVE IT.

Don't be afraid to adjust the makeup gain as you follow this procedure. Volume has a big impact on your perception so keep it constant to help with decision making.

I could write a book on this subject but this method gives you very transparent sound. More importantly it highlights how each parameter of a compressor works.
There are aspects of using compressors to help gel a mix involving attack, release and sidechain. Best left alone for now....

 

[crabtwins]

hey thats awesome thanks for the tips on setting compressor i printed it out.

 

[pingu]

read this


http://recforums.prosoundweb.com/index.php/t/10765/13127/

 

[MessianicDreams]

1. The threshold is the level at which compression is supposed to start. So then why do I see some gain reduction meter jumping (albeit small) for a signal that is below threshold. I have heard that compression squashes the loud and lifts the low, but I thought the lifting of the low was a perception effect of squashing the loud?

yeh, someone hit this one on the head. soft knee compression means that the comp will kick in slightly below your thresh. it also means that compression won't be linear, despite a supposed "linear" ratio.

2. Any ideas on understanding (mathematically) the link between release and attack? For instance I know that t=1/f does knowing that help me understand the setting of release and attack for a certain sound, for instance bass?

i would suggest that you don't sit down with a calculator when you come to mix, but rather rely on your ears as to what sounds the best to you on the given program material.

3. Does release time begin when attack starts or is it measured from when the threshold is hit?

just wanted to clear this bit up, release time starts when the threshold has been crossed for the second time (ie the sound has gone lower than the thresh), and it is the time taken for complete gain reduction release (how long the compressor takes to totally stop working).