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Author Topic: Practical use of downward expansion help me understand  (Read 1811 times)

Scott Olewiler

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Practical use of downward expansion help me understand
« on: October 21, 2018, 09:32:49 am »

Where does everyone find using downward expansion is better than using tradition gates and why? 
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John Roberts {JR}

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Re: Practical use of downward expansion help me understand
« Reply #1 on: October 21, 2018, 10:04:12 am »

Where does everyone find using downward expansion is better than using tradition gates and why?
Downward expansion gives a more subtle fading down of the noise floor instead of the abrupt on/off of a noise gate. 

JR
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dave briar

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Re: Practical use of downward expansion help me understand
« Reply #2 on: October 21, 2018, 11:44:56 am »

Downward expansion gives a more subtle fading down of the noise floor instead of the abrupt on/off of a noise gate. 

JR
I defer to those more knowledgeable but can't the same response be achieved via setting the attack, hold, and release values on the gate?
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Scott Olewiler

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Practical use of downward expansion help me understand
« Reply #3 on: October 21, 2018, 12:11:00 pm »

Downward expansion gives a more subtle fading down of the noise floor instead of the abrupt on/off of a noise gate. 

JR
John, Thanks but I already understand what it does.

I was more interested in what practical applications folks use it  over gates? Where do people find it more useful.
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Chris Hindle

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Re: Practical use of downward expansion help me understand
« Reply #4 on: October 21, 2018, 12:43:54 pm »

John, Thanks but I already understand what it does.

I was more interested in what practical applications folks use it  over gates? Where do people find it more useful.

Quiet Jazz, quiet hall, with a noisy band.
No, it makes no sense, but I got good results anyway.
Chris.
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Rick Powell

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Re: Practical use of downward expansion help me understand
« Reply #5 on: October 21, 2018, 10:31:09 pm »

John, Thanks but I already understand what it does.

I was more interested in what practical applications folks use it  over gates? Where do people find it more useful.

I use downward expansion more in recording where the abruptness of a gate causes issues that are more noticeable than with a live situation.
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Luke Geis

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Re: Practical use of downward expansion help me understand
« Reply #6 on: October 22, 2018, 02:05:27 pm »

It has a few upsides, most notably with things like drums, vocals or spoken word in noisy environments.

It is not like a gate although in principle that is what it is. A gate is more abrupt and doesn't have a ratio making it more like a switch with parameters to make it less noticeable or more controlled. An expander is more like a reverse compressor. It has a ratio, attack, release, and range ( db reduction amount ), and is much more subtle at opening and closing making it more natural and useful for things that are more sensitive to an on-off sound.

The Neve 5045 Primary Source Enhancer, in essence, is a glorified expander with fewer knobs. When most of us hear downward expansion we think more like a gate, but that is not what it is. Downward expansion should be thought of as more like downward compression, or decompression. As the signal gets quieter the output level is reduced more and more in relation to the ratio and threshold setting we use. The range sets the amount of db reduction and the attack and release times adjust the softness of the on-off nature of the compressor.

If used well you can get up to 10db more gain before feedback in touchy situations, but you have to be careful. The concept is simple. When the person is not talking the gain is reduced and feedback is staved, as soon as the person talks the expander opens up and you get full output again. If set up well, you can get a little more volume without feedback. For drums, you can use it to reduce background noise and tighten up the drum mix. With noisy stages and background vocals, you can use it to at the very least duck out some of the stage wash when the background singers are not on the mic.

Think of an expander as more of a compressor in reverse. It simply reduces the noise floor by compressing it into a smaller dynamic range. As the signal gets quieter it drags the signal down more quickly to the noise floor which you set. As the signal gets louder ( in relation to the noise floor ) the expander drags the noise floor up ( opens ) and the signal is released from the expander. There is a makeup gain feature as well. Again an expander is designed to act more like a compressor. The makeup gain increases the output as you can imagine by the set amount. This brings the noise floor up with it. The range sets where the noise floor is and the ratio and threshold settings set the db level where the expander starts to uncompress. This is what allows you to make the quiet things louder in relation to the noise floor, hence the term expander.
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Helge A Bentsen

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Re: Practical use of downward expansion help me understand
« Reply #7 on: October 22, 2018, 02:41:45 pm »

I use it sometimes on inconsistent drummers. First an expander, then a gentle compressor to keep the levels in check.

Works magic when you're doing a birthday gig or a corporate show where the customer brings his own "band".
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Doug Johnson

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Re: Practical use of downward expansion help me understand
« Reply #8 on: October 22, 2018, 04:07:02 pm »

I have found that downward expansion works really well on podium mics in windy conditions.
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John Roberts {JR}

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Re: Practical use of downward expansion help me understand
« Reply #9 on: October 22, 2018, 05:28:39 pm »

It has a few upsides, most notably with things like drums, vocals or spoken word in noisy environments.

It is not like a gate although in principle that is what it is. A gate is more abrupt and doesn't have a ratio making it more like a switch with parameters to make it less noticeable or more controlled. An expander is more like a reverse compressor. It has a ratio, attack, release, and range ( db reduction amount ), and is much more subtle at opening and closing making it more natural and useful for things that are more sensitive to an on-off sound.

The Neve 5045 Primary Source Enhancer, in essence, is a glorified expander with fewer knobs. When most of us hear downward expansion we think more like a gate, but that is not what it is. Downward expansion should be thought of as more like downward compression, or decompression.
The name expander is literal and accurate, it "expands" the dynamic range the reciprocal or inverse function of compression. 
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As the signal gets quieter the output level is reduced more and more in relation to the ratio and threshold setting we use. The range sets the amount of db reduction and the attack and release times adjust the softness of the on-off nature of the compressor.
for people who remember dbx tape noise reduction, that was basically a 2:1 compressor before the tape path, and 1:2 expander after. The 1:2 expander made the loud louder, and the quiet, quieter while making the tape hiss quieter too. 
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If used well you can get up to 10db more gain before feedback in touchy situations, but you have to be careful. The concept is simple. When the person is not talking the gain is reduced and feedback is staved, as soon as the person talks the expander opens up and you get full output again. If set up well, you can get a little more volume without feedback.

I would advise caution about this or any dynamic gain ranging in a monitor system path (dynamically changing gain is often a recipe for instability).
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For drums, you can use it to reduce background noise and tighten up the drum mix. With noisy stages and background vocals, you can use it to at the very least duck out some of the stage wash when the background singers are not on the mic.
more of a recording tool than live, but the OP asked.
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Think of an expander as more of a compressor in reverse. It simply reduces the noise floor by compressing it into a smaller dynamic range. As the signal gets quieter it drags the signal down more quickly to the noise floor which you set. As the signal gets louder ( in relation to the noise floor ) the expander drags the noise floor up ( opens ) and the signal is released from the expander. There is a makeup gain feature as well.
??
Quote
Again an expander is designed to act more like a compressor.
inverse of a compressor
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The makeup gain increases the output as you can imagine by the set amount. This brings the noise floor up with it. The range sets where the noise floor is and the ratio and threshold settings set the db level where the expander starts to uncompress. This is what allows you to make the quiet things louder in relation to the noise floor, hence the term expander.
The nomenclature comes from the simple fact that it "expands" the dynamic range.

Compression makes the quiet bits louder and easier to hear... unfortunately this also boosts up the noise floor, so downward expansion when used correctly can restore the noise floor to it's appropriate level wrt signal. Again more of a recording than live sound issue. 

I have actually built downward expansion into compressors to restore the noise floor down where it should be, but made it transparent to the operator hoping to KISS. What they don't know can help them. 8)

For live sound, SR gates are generally faster and easier to set up. The benefit of downward expansion is marginal compared to the extra time and effort. 

JR   
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Jon Brunskill

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Re: Practical use of downward expansion help me understand
« Reply #10 on: October 23, 2018, 05:47:46 am »

This is probably a dumb question, but what is the difference between using an expander and a 'gentle' gate?

I never, ever set a gate to mute - I set them for say, 6ish db cut when the sound is below the threshold. It makes sense to me that the kick drum doesn't have to mute in between hits, it just has to duck the volume a little bit, which gives the effect of a tighter sound without the clicky abrupt hard gate sound.

Isn't this what an expander does anyway?
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David Morison

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Re: Practical use of downward expansion help me understand
« Reply #11 on: October 23, 2018, 08:58:25 am »

This is probably a dumb question, but what is the difference between using an expander and a 'gentle' gate?

I never, ever set a gate to mute - I set them for say, 6ish db cut when the sound is below the threshold. It makes sense to me that the kick drum doesn't have to mute in between hits, it just has to duck the volume a little bit, which gives the effect of a tighter sound without the clicky abrupt hard gate sound.

Isn't this what an expander does anyway?

I'd argue that if a "gate" allows the gain reduction to be tailored that finely, it has already become a downward expander, regardless of what the name on the faceplate/plugin says.

The classic BSS 504 for example only offered a switchable choice of 70 or 20dB range.

Whether or not arguing semantics over nomenclature is worth it or not, is another question.

Bottom line, you've found a way of using the available control to get as smooth & natural sound as possible.
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John Roberts {JR}

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Re: Practical use of downward expansion help me understand
« Reply #12 on: October 23, 2018, 10:13:36 am »

This is probably a dumb question, but what is the difference between using an expander and a 'gentle' gate?

I never, ever set a gate to mute - I set them for say, 6ish db cut when the sound is below the threshold. It makes sense to me that the kick drum doesn't have to mute in between hits, it just has to duck the volume a little bit, which gives the effect of a tighter sound without the clicky abrupt hard gate sound.

Isn't this what an expander does anyway?
This is getting pedantic and perhaps semantic but a gate is characterized by snapping on/off (even only -6 dB), while an expander smoothly drops X dB per Y dB of signal drop...

Don't worry about the small stuff...

JR

PS: Your -6dB gate could click on a low level sine wave, less likely to be heard clicking on wide band noise.
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Nathan Riddle

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Re: Practical use of downward expansion help me understand
« Reply #13 on: October 23, 2018, 12:57:11 pm »

Isn't the ratio and hold the only control difference between the two?

A full-featured gate:
-threshold
-attack
-hold
-release
-depth

A full-featured downward expander:
-threshold
-attack
-release
-ratio
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Art Welter

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Re: Practical use of downward expansion help me understand
« Reply #14 on: October 23, 2018, 01:57:53 pm »

Isn't the ratio and hold the only control difference between the two?

A full-featured gate:
-threshold
-attack
-hold
-release
-depth

A full-featured downward expander:
-threshold
-attack
-release
-ratio
Nathan,

To be effective, a "full featured" gate also requires frequency filters on the threshold.

The differences between "downward expansion" and "noise gate" can become semantic, like the difference between "compression" and "limiting".
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John Roberts {JR}

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Re: Practical use of downward expansion help me understand
« Reply #15 on: October 23, 2018, 02:44:03 pm »

Nathan,

To be effective, a "full featured" gate also requires frequency filters on the threshold.

The differences between "downward expansion" and "noise gate" can become semantic, like the difference between "compression" and "limiting".
first I have also provided adjustable depth on downward expanders but agree too many controls can be counter productive (KISS).  FWIW premium full feature gates can also add some look-ahead delay/anticipation, to open more cleanly.

===

I suspect these days with more such dynamics being performed inside the digital domain there is no significant cost difference between smooth downward expansion and hard noise gating, perhaps some slight processor overhead but that is surely inexpensive. So differences are perhaps in what they call them... ::)

JR
 
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Scott Helmke

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Re: Practical use of downward expansion help me understand
« Reply #16 on: October 25, 2018, 02:53:23 pm »

The Neve 5045 Primary Source Enhancer, in essence, is a glorified expander with fewer knobs.

The 5045 is a rather interesting item, and very effective at squeezing a few more dB out of a lectern mic.
But when I don't have one of those (most of the time), I use an expander with settings to get roughly the same result. 

On a Yamaha desk it's a very low ratio (1.1:1 or so), and somewhat quick attack and release. The goal is to drop the noise floor between words without it sounding too unnatural.
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Luke Geis

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Re: Practical use of downward expansion help me understand
« Reply #17 on: October 28, 2018, 02:17:25 pm »

I think the biggest difference between gates and expanders are that it is nearly impossible to get an expander to bounce. We have all probably heard of gate bouncing or gate chatter and perhaps even experienced it. Expanders don't truly mute audio and since some of the functions are different, it is very difficult to get chatter out of them.

I have been using expanders more and more lately for spoken word because you can eek several db more gain before feedback. This combined with a multiband compressor can really get most of the work done before you even touch an EQ. With LAVS this is especially helpful in keeping as much gain as possible and achieving a more natural sound.
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John Roberts {JR}

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Re: Practical use of downward expansion help me understand
« Reply #18 on: October 28, 2018, 02:47:38 pm »

I think the biggest difference between gates and expanders are that it is nearly impossible to get an expander to bounce. We have all probably heard of gate bouncing or gate chatter and perhaps even experienced it. Expanders don't truly mute audio and since some of the functions are different, it is very difficult to get chatter out of them.
It is pretty common practice when designing noise gates to add hysteresis to the threshold, so that once open it has to drop several dB more below threshold before closing again. Along with hold time, and slow release this can generally suppress all but the worst gate chatter.   
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I have been using expanders more and more lately for spoken word because you can eek several db more gain before feedback. This combined with a multiband compressor can really get most of the work done before you even touch an EQ. With LAVS this is especially helpful in keeping as much gain as possible and achieving a more natural sound.
I remain apprehensive about adding dynamic gain changes in any audio loop susceptible to feedback. Compression in such a path is notorious for causing feedback when the primary signal drops off and the gain increases. Complementary downward expansion could cancel that compressor gain increase while releasing but may not be easy to coordinate. I think I shared earlier I have incorporated downward expansion inside compressors (transparently) before precisely to thwart the noise floor build up when signal fades, but I never advocated using even them in a monitor path.

I won't argue with you about what works for you, in theory it could improve your results if you are already using a compressor in the same path. It seems you may be mitigating a problem you caused with the compression.

JR

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drew gandy

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Re: Practical use of downward expansion help me understand
« Reply #19 on: February 09, 2019, 12:16:47 pm »

The 5045 is a rather interesting item, and very effective at squeezing a few more dB out of a lectern mic.
But when I don't have one of those (most of the time), I use an expander with settings to get roughly the same result. 

On a Yamaha desk it's a very low ratio (1.1:1 or so), and somewhat quick attack and release. The goal is to drop the noise floor between words without it sounding too unnatural.

So...  Neve released the 545 last year.  It's a single channel "Primary Source Enhancer" in a 500 series module.  Interestingly, it appears to be missing the time constant knob.  Anyone seen these in their hands yet?  Any comments? 
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