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Author Topic: First Attempt at Compression  (Read 1094 times)

Isaac South

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First Attempt at Compression
« on: February 13, 2018, 10:48:10 am »

I’ve been reading/studying about compression.  Trying to learn about it as much as I can.  I’m not 100% confident that I know what all the compression terms mean.  But last night, I had the opportunity to not be on-stage, and I was able to mix FOH (church service).  So, I took the liberty of playing around with the compression (for the first time) on our preacher’s signal.  We use a QU-32 mixer.  I was finally able to put my knowledge to practice, and I wanted to make a post to confirm everything that I’ve learned.  If I’ve got something wrong, please tell me.  That’s the whole reason I’m posing this.

Threshold - In my mind, the threshold, is the db level at which the compression kicks-in.  So, I had our preacher set to -0.5db.  And when he reached that db, the compression kicked in and “lowered his volume”.  I realize my wording is very amateur.  Forgive me.  I noticed, that the higher this was set, the less the compression kicked it.  Am I seeing this correctly?  I don’t understand HOW it works on -0.5db.  Where is it getting that db reading from?  It sure sounded like a lot more db than -0.5 when the compression kicked it.  Can someone help me understand the meaning of db here?

Ratio – I had this set to 4:1.  I don’t particularly understand this one fully.  I used a 4:1 simply because someone on the forum mentioned it.  Based on my reading, it means: for everyone 4 db over the threshold, only 1 db passes through.  So 4 compressed to 1.   But I don’t really know how to apply that.  I want our preacher to have the ability to increase in level at times.  For example, when he is preaching the climax of his message the crowd gets with him (yelling amen, clapping, etc).  So I want his signal to be able to get louder than the excited crowd.  But still compressed.

Gain – This one was the most useful for me.  When the preacher would hold the mic down lower, and I increased this gain, his level would go up.  This was really cool, and most noticeable to me, because it allowed the audience to hear him very clearly, even though his mic was pulled farther away from his mouth.  We have a very dynamic preacher.   And then, when he would put the mic close to his mount and raise his voice, we still weren’t being killed with increased level.  This is why compression is cool to me.  I was very excited last night, when I started noticing this.

Attack – This is how fast the signal is compressed.  I just left this where it was (roughly 4.5 ms).  Seemed fast to me.  But not compared to the speed of the release. 

Release – This is how quick the compressed stops compressing.  I left this one alone as well.  It was set at 150ms.  That seems super super fast.  By the way, why is the attack time and release time allowed to be so different in speed.  You’d think they would be close.  Or maybe they should be, and I just didn’t play around with the different speeds.

Hard Knee/Soft Knee -  This is something I know nothing about.  And furthermore, I can’t tell which one I’m on.  When I look at the screen it shows “hard knee”.  Does that mean “hard knee” is on, or does it mean I need to push “hard knee” to turn it on?  This may be a question for A&H, unless someone else uses this mixer and can advise me.

I appreciate anything I can learn from you guys/gals.  Thank you for your time.  I’m sorry for the long post.
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John Roberts {JR}

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Re: First Attempt at Compression
« Reply #1 on: February 13, 2018, 10:58:02 am »

This is incredibly basic stuff but the simple answer is that compression, "compresses" or reduces the dynamic range of the output compared to the input (makes the loud parts less loud). An above threshold compressor leaves the low level parts alone while reducing the loud parts. The threshold establishes when the compressions starts reducing gain, and ratio establishes how much... For example a 2:1 compressions ratio means a 2 dB change (above threshold) only causes a 1 dB change at the output.

Attack/release refer to side chain time constants for how fast it will reduce gain steps, and then recover again.

Hard knee/vs soft knee refers to how it behaves around the threshold... soft knee is "softer" duh.

JR 
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On the internet people tell you everything "they" know, not the answer to "your" question.

Geert Friedhof

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Re: First Attempt at Compression
« Reply #2 on: February 13, 2018, 11:26:21 am »

Attack time: The time the compressor takes to compress to full compression, allowing for some dynamics, for drums etc. If too long pops etc can come through before the compressor fully compresses.

Release time: the time the compressor takes to go back to no compression.

For your pastor, i would set the attack very short (1-3ms), and the release at 12-15ms, but be careful not to get a 'pumping' sound. Ratio: try 2.5.

A longer release and/or a smaller ratio will allow for a more dynamic performance, whilst still being controlled. Just play with it.

Soft knee: around the threshold the compressor compresses a little bit less, making the threshold less audible.  Make sure it is set at soft knee.

One last tip: Don't overdo it! A good compressor is one that does its job, but can't be heard.
« Last Edit: February 13, 2018, 11:30:21 am by Geert Friedhof »
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Joe Pieternella

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Re: First Attempt at Compression
« Reply #3 on: February 13, 2018, 01:18:53 pm »

Your understanding of what the threshold is is correct. The dB reading seems to be confusing you though. All dB values are relative to a reference. The db values you were seeing are relative to dBu not dB SPL. Personally I would set the threshold mostly by ear anyway.

Tip: for these purposes I try to make sure the comp isn't working all the time(the red meter not constantly on). This means that he still has some control over his overall level, you just compress the peaks but allow him to raise his average level by speaking louder.

Tip nr2 a good way to find out what part of the signal the compressor isn't reacting to is setting the tresshold as low as it will go, attack and release as fast as possible and the ratio as high as possible. And then adjust attack and release and listen to the signal that gets through.
I DON'T RECOMMEND DOING THIS IN A LIVE SITUATION. Unless you feel like getting some very weird looks from the congregation.



Verstuurd vanaf mijn G8341 met Tapatalk
« Last Edit: February 13, 2018, 01:25:29 pm by Joe Pieternella »
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Tim McCulloch

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Re: First Attempt at Compression
« Reply #4 on: February 13, 2018, 01:38:07 pm »

Go to dbxpro.com and download the user manual for the dbx 1066.  Ignore the parts about the expander/gate and dbx proprietary stuff like the PeakStop limiter.

The manual is a thorough explanation of what each parameter does and how it interacts with other parameters.  They have graphics to illustrate.

If you have a recording of your pastor (or any presenter with similar dynamics) play it back through an input channel, put on your headphones and solo/PFL the input to clearly hear the changes as you manipulate the threshold, attack, release, ratio and knee parameters...

As JR pointed out, the Threshold is the signal level at which the compressor begins its work; Ratio is the amount of signal *above threshold level* that will result in a +1dB change in the compressor's output.  Attack is the amount of time before the compressor will act on a signal that exceeds threshold.  Release is the amount of time the compressor will continue its level reduction after the input signal drops below threshold.

Does your pastor have a lot of his voice in the platform monitors?  If so, compressing his signal may mess with his perception of his voice, much like compressing a singer in his/her monitor can cause them to over-sing when they don't hear the monitor get louder as they sing harder...  If he's not one of the preachers who has to feel his voice on his body, you're probably okay.  Either way, though, I suggest you consult the mixer manual and determine if the channel strip compressors are before or after the mix/aux/monitor (whatever AH calls them) sends.  If the compressor's place in the signal chain is before those, the compressed signal will feed them, if it's after the sends, the uncompressed signal will feed the sends.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Isaac South

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Re: First Attempt at Compression
« Reply #5 on: February 13, 2018, 02:19:18 pm »

Your understanding of what the threshold is is correct. The dB reading seems to be confusing you though. All dB values are relative to a reference. The db values you were seeing are relative to dBu not dB SPL. Personally I would set the threshold mostly by ear anyway.

Tip: for these purposes I try to make sure the comp isn't working all the time(the red meter not constantly on). This means that he still has some control over his overall level, you just compress the peaks but allow him to raise his average level by speaking louder.

Tip nr2 a good way to find out what part of the signal the compressor isn't reacting to is setting the tresshold as low as it will go, attack and release as fast as possible and the ratio as high as possible. And then adjust attack and release and listen to the signal that gets through.
I DON'T RECOMMEND DOING THIS IN A LIVE SITUATION. Unless you feel like getting some very weird looks from the congregation.



Verstuurd vanaf mijn G8341 met Tapatalk

Great information, Joe.  Thanks for this.  You cleared up the db confusion for me.  I agree with you that compression shouldn't be working all the time.  We want dynamics, but not peaks.  Thanks for clearing that up for me.
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Isaac South

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Re: First Attempt at Compression
« Reply #6 on: February 13, 2018, 02:37:39 pm »

Go to dbxpro.com and download the user manual for the dbx 1066.  Ignore the parts about the expander/gate and dbx proprietary stuff like the PeakStop limiter.

The manual is a thorough explanation of what each parameter does and how it interacts with other parameters.  They have graphics to illustrate.

If you have a recording of your pastor (or any presenter with similar dynamics) play it back through an input channel, put on your headphones and solo/PFL the input to clearly hear the changes as you manipulate the threshold, attack, release, ratio and knee parameters...

As JR pointed out, the Threshold is the signal level at which the compressor begins its work; Ratio is the amount of signal *above threshold level* that will result in a +1dB change in the compressor's output.  Attack is the amount of time before the compressor will act on a signal that exceeds threshold.  Release is the amount of time the compressor will continue its level reduction after the input signal drops below threshold.

Does your pastor have a lot of his voice in the platform monitors?  If so, compressing his signal may mess with his perception of his voice, much like compressing a singer in his/her monitor can cause them to over-sing when they don't hear the monitor get louder as they sing harder...  If he's not one of the preachers who has to feel his voice on his body, you're probably okay.  Either way, though, I suggest you consult the mixer manual and determine if the channel strip compressors are before or after the mix/aux/monitor (whatever AH calls them) sends.  If the compressor's place in the signal chain is before those, the compressed signal will feed them, if it's after the sends, the uncompressed signal will feed the sends.

Tim - I will read this tonight.  Thank you for pointing me to that resource.  What you are saying about the compressor being before or after the monitor sends, makes sense.  I actually thought about that last night.  You're right:  I don't want the monitors compressed.  Thanks for your help, Tim.
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Jerome Malsack

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Re: First Attempt at Compression
« Reply #7 on: February 13, 2018, 03:15:25 pm »

Another good point is what is your mixer and what is the compressor,  If digital mixer with built in compressor.  make and model.  helps us also when answering the questions. 

Some added good tools. 

http://www.rane.com/library.html
http://www.rane.com/note155.html

http://www.rane.com/note109.html
http://www.rane.com/note110.html




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Isaac South

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Re: First Attempt at Compression
« Reply #8 on: February 13, 2018, 09:42:52 pm »

Another good point is what is your mixer and what is the compressor,  If digital mixer with built in compressor.  make and model.  helps us also when answering the questions. 

Some added good tools. 

http://www.rane.com/library.html
http://www.rane.com/note155.html

http://www.rane.com/note109.html
http://www.rane.com/note110.html

We have the QU-32 Allen and Heath


Sent from my iPhone using Tapatalk
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Geert Friedhof

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Re: First Attempt at Compression
« Reply #9 on: February 13, 2018, 09:54:00 pm »

Another good point is what is your mixer and what is the compressor,  If digital mixer with built in compressor.  make and model.  helps us also when answering the questions. 

Some added good tools. 

http://www.rane.com/library.html
http://www.rane.com/note155.html

http://www.rane.com/note109.html
http://www.rane.com/note110.html

Or you just read the thread...
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