Compression question

[James Price[_5_]]

Compression is generally thought of as reducing dynamic range. However, let's say I've got a guitar amplifier that puts out pretty much the same volume when I pick lightly in the entire range from "light" to "soft-medium" (using an arbitrary input scale from 0dB to 3dB). If I put a compressor post-amp and side-chain it to my guitar input I could run it ducked whereby it's only active when the input is below 3dB on that arbitrary scale. Have I not expanded the lower threshold of my dynamic range?

[Les Cargill[_4_]]

James Price wrote:
> Compression is generally thought of as reducing dynamic range.
> However, let's say I've got a guitar amplifier that puts out pretty
> much the same volume when I pick lightly in the entire range from
> "light" to "soft-medium" (using an arbitrary input scale from 0dB to
> 3dB). If I put a compressor post-amp and side-chain it to my guitar
> input I could run it ducked whereby it's only active when the input
> is below 3dB on that arbitrary scale. Have I not expanded the lower
> threshold of my dynamic range?
>



I wouldn't even bother with the compressor. Just drop a DI and mix
that in with the amp's signal.

--
Les Cargill

[geoff]

On 12/08/2017 2:11 PM, Les Cargill wrote:
> James Price wrote:
>> Compression is generally thought of as reducing dynamic range.
>> However, let's say I've got a guitar amplifier that puts out pretty
>> much the same volume when I pick lightly in the entire range from
>> "light" to "soft-medium" (using an arbitrary input scale from 0dB to
>> 3dB). If I put a compressor post-amp and side-chain it to my guitar
>> input I could run it ducked whereby it's only active when the input
>> is below 3dB on that arbitrary scale. Have I not expanded the lower
>> threshold of my dynamic range?
>>
>
>
>
> I wouldn't even bother with the compressor. Just drop a DI and mix
> that in with the amp's signal.
>


Read some magazines. Beware that there might be some degree of
exaggeration and bull****, but possibly less than with a shop salesman.

geoff

[geoff]

On 13/08/2017 7:28 PM, geoff wrote:
>
> Read some magazines. Beware that there might be some degree of
> exaggeration and bull****, but possibly less than with a shop salesman.
>
> geoff


Ooops, right answer, wrong question !

geoff

[Scott Dorsey]

James Price > wrote:
>Compression is generally thought of as reducing dynamic range. However, let=
>'s say I've got a guitar amplifier that puts out pretty much the same volum=
>e when I pick lightly in the entire range from "light" to "soft-medium" (us=
>ing an arbitrary input scale from 0dB to 3dB). If I put a compressor post-a=
>mp and side-chain it to my guitar input I could run it ducked whereby it's =
>only active when the input is below 3dB on that arbitrary scale. Have I not=
> expanded the lower threshold of my dynamic range?

With a compressor, the _more_ signal going into the sidechain input, the
more it compresses. So you can't set it up so it compresses below the
threshold and not above.

What you are describing is called an expander.

Many dbx compressors have expander functions, and there are some devices
out there that are generic dynamic control modules. Some of those get
called compressors rather than companders or dynamic controllers, even
though they can do far more than compress. This is because "Compressor"
is simple and easy to say and looks good on a tear sheet.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[[email protected]]

>
> With a compressor, the _more_ signal going into the sidechain input, the
> more it compresses. So you can't set it up so it compresses below the
> threshold and not above.

but you can do this

https://en.wikipedia.org/wiki/Parallel_compression

m

[Phil Allison[_4_]]

Scott Dorsey wrote:

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

>
> What you are describing is called an expander.
>
> Many dbx compressors have expander functions,
>


** LOL - intentional or otherwise !!

" dbx " actually stands for "decibel expansion" as the companies first products were compressor /expanders ( aka companders) for noise reduction when used with cassette decks.

Later they went for the pro audio market with the dbx160 compressor/limiter -
which would act as an expander when set for hard limiting.

Reason being it lacked a fast enough attack time to actually compress speech or music properly. Instead, it simply passed signal transients through while reducing the level of the steadier signals that followed.

With popular music or speech it would INCREASE the peak to average margin by
up to 10dB. A fact easily verified by comparing the readings on a regular VU with those on a peak VU before and after processing by a dbx160.

There were numerous other models that did exactly the same too.



..... Phil

[Trevor]

On 15/08/2017 3:11 AM, wrote:
>> With a compressor, the _more_ signal going into the sidechain input, the
>> more it compresses. So you can't set it up so it compresses below the
>> threshold and not above.
>
> but you can do this
>
> https://en.wikipedia.org/wiki/Parallel_compression
>

It's strange to see people still using analog style techniques to do
what has been easy in the digital processing domain of a DAW for a
couple of decades. One can simply draw a compression curve that has a
knee at the bottom end rather than the top if that's where you want the
most compression. No need for all the extra stuffing around.

Trevor.

[Mike Rivers[_2_]]

On 8/15/2017 12:21 AM, Phil Allison wrote:
> dbx " actually stands for "decibel expansion" as the companies first products were compressor /expanders ( aka companders) for noise reduction when used with cassette decks.
>
> Later they went for the pro audio market with the dbx160 compressor/limiter -
> which would act as an expander when set for hard limiting.
>
> Reason being it lacked a fast enough attack time to actually compress speech or music properly. Instead, it simply passed signal transients through while reducing the level of the steadier signals that followed.
>
> With popular music or speech it would INCREASE the peak to average margin by
> up to 10dB. A fact easily verified by comparing the readings on a regular VU with those on a peak VU before and after processing by a dbx160.
>
> There were numerous other models that did exactly the same too.


Well .... you've just described how and why most people use compressors
today. By sitting on high the levels of a waveform. the overall output
level can be (and is) raised which brings up the lower level content
without exceeding the maximum output level.

The attack and release time controls provide the ability to delay the
onset of gain reduction in order to let the attack of a note through
while controlling the level of the sustained part of the note. This is
what makes snare drums crack and kick drums bloom. But it doesn't do
anything natural-sounding to a voice. If you want to even out a
vocalist's screams and swallowed words you need a different balance of
attack and release times. Often, devices intended as levelers have fixed
settings. They often are abused to produce interesting, though
unnatural-sounding effects.

Now why are we talking about this? I think because there's a difference
between "just draw the curve," experimenting with hardware while
listening until you say "Eureka! That's the sound I'm after!," and "I
always use put an 1176 after the 1073 when I track vocals."


--

For a good time, call http://mikeriversaudio.wordpress.com

[[email protected]]

On Tuesday, August 15, 2017 at 3:04:52 AM UTC-4, Trevor wrote:
> On 15/08/2017 3:11 AM, wrote:
> >> With a compressor, the _more_ signal going into the sidechain input, the
> >> more it compresses. So you can't set it up so it compresses below the
> >> threshold and not above.
> >
> > but you can do this
> >
> > https://en.wikipedia.org/wiki/Parallel_compression
> >
>
> It's strange to see people still using analog style techniques to do
> what has been easy in the digital processing domain of a DAW for a
> couple of decades. One can simply draw a compression curve that has a
> knee at the bottom end rather than the top if that's where you want the
> most compression. No need for all the extra stuffing around.
>
> Trevor.

Can you draw a curve on a DAW compressor that gives you the same effect as parallel compression described in the article without actually creating a parallel path.

I never thought about it before ....I suppose you can!

I guess it would need 2 knees with an almost flat portion someplace in the middle.

thanks for the idea

m

[Phil Allison[_4_]]

Mike Rivers wrote:

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

>
> > dbx " actually stands for "decibel expansion" as the companies first products were compressor /expanders ( aka companders) for noise reduction when used with cassette decks.
> >
> > Later they went for the pro audio market with the dbx160 compressor/limiter -
> > which would act as an expander when set for hard limiting.
> >
> > Reason being it lacked a fast enough attack time to actually compress speech or music properly. Instead, it simply passed signal transients through while reducing the level of the steadier signals that followed.
> >
> > With popular music or speech it would INCREASE the peak to average margin by
> > up to 10dB. A fact easily verified by comparing the readings on a regular VU with those on a peak VU before and after processing by a dbx160.
> >
> > There were numerous other models that did exactly the same too.
>
>
> Well .... you've just described how and why most people use compressors
> today.
>

** You have completely misread my words.


> By sitting on high the levels of a waveform. the overall output
> level can be (and is) raised which brings up the lower level content
> without exceeding the maximum output level.
>


** That is the direct OPPOSITE of what happens !!!!

The peaks go unaltered because of the slow response of the detector while lower levels are *reduced* when gain reduction finally kicks in.


> The attack and release time controls ....


** The dbx 160 and its near relatives have NO such controls.


> provide the ability to delay the
> onset of gain reduction in order to let the attack of a note through
> while controlling the level of the sustained part of the note.


** Gobbledegook.

Slow attack compressors suffer from a phenomenon called "inversion", they become expanders instead.

Fast attack is essential to creating "peak limiting".


..... Phil







...... Phil

[Scott Dorsey]

> wrote:
>
>Can you draw a curve on a DAW compressor that gives you the same effect as parallel compression described in the article without actually creating a parallel path.
>
>I never thought about it before ....I suppose you can!

You can, the basic idea behind parallel compression is to change the shape
of the curve.

There have been a few fancy compressors out there that let you set up a
curve with multiple knees and strange shapes (and maybe even an inverted
curve so it expands at low levels). But it's much easier to do this fancy
stuff in the digital domain.

>I guess it would need 2 knees with an almost flat portion someplace in the middle.
>
>thanks for the idea

You can also, of course, make a stem with compressed signal mixed with the
original signal and so forth if you like working that way.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Phil Allison > wrote:
>Slow attack compressors suffer from a phenomenon called "inversion", they become expanders instead.

This is a matter of using the wrong tool for the job. There are plenty of
reasons you might want a slow compressor that allows a huge leading peak
through, for example to make drums more clicky. It's a tool for a job,
just not necessarily the one you're thinking of.

>Fast attack is essential to creating "peak limiting".

I tend to think of limiting and compression as two different animals that
you use for different reasons. And I tend to think of an AGC device as a
third different thing. They are all dynamics control devices, and they all
reduce the level of signals in proportion to the input level, but they are
different tools for different jobs.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[[email protected]]

Scott Dorsey:

Limiting is, and always will be, a form of
compression. It is reducing the diffference
between two parts of a sound, just as
regular compression does.

[Scott Dorsey]

> wrote:
>Scott Dorsey:
>
>Limiting is, and always will be, a form of
>compression. It is reducing the diffference
>between two parts of a sound, just as
>regular compression does.

By definition: limiting has a hard knee and a fast attack, and it exists
to limit peaks.

Compression is used for a lot of things, and as Phil noted, many compressors
have RMS detectors and slow operation and wind up exaggerating peaks rather
than reducing them.

An AGC compressor is used for totally different applications than a limiter,
its circuitry is totally different, and its effect on sound is totally
different.

Many limiters don't even _have_ a control path, just a single nonlinear
stage or even just a clamp.

So no, I'd put compression and limiting in very different categories. Which
is why we often have a compressor preceding a limiter (and sometimes an AGC
device before the pair).
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[[email protected]]

On Tuesday, August 15, 2017 at 10:03:39 AM UTC-4, Scott Dorsey wrote:
> > wrote:
> >
> >Can you draw a curve on a DAW compressor that gives you the same effect as parallel compression described in the article without actually creating a parallel path.
> >
> >I never thought about it before ....I suppose you can!
>
> You can, the basic idea behind parallel compression is to change the shape
> of the curve.
>
> There have been a few fancy compressors out there that let you set up a
> curve with multiple knees and strange shapes (and maybe even an inverted
> curve so it expands at low levels). But it's much easier to do this fancy
> stuff in the digital domain.
>
> >I guess it would need 2 knees with an almost flat portion someplace in the middle.
> >
> >thanks for the idea
>
> You can also, of course, make a stem with compressed signal mixed with the
> original signal and so forth if you like working that way.
> --scott


no I don't like to use parallel paths...

too many opportunities for latency to cause comb filtering issues.
especially in digital land.

I will try creating the appropriate curve to give the same effect as parallel compression without the parallel paths.

m

[[email protected]]

On Friday, August 11, 2017 at 10:09:04 PM UTC-4, Les Cargill wrote:
> James Price wrote:
> > Compression is generally thought of as reducing dynamic range.
> > However, let's say I've got a guitar amplifier that puts out pretty
> > much the same volume when I pick lightly in the entire range from
> > "light" to "soft-medium" (using an arbitrary input scale from 0dB to
> > 3dB). If I put a compressor post-amp and side-chain it to my guitar
> > input I could run it ducked whereby it's only active when the input
> > is below 3dB on that arbitrary scale. Have I not expanded the lower
> > threshold of my dynamic range?
> >
>
>
>
> I wouldn't even bother with the compressor. Just drop a DI and mix
> that in with the amp's signal.
>
> --
> Les Cargill

What happened to the original post!!??

I was here, then vanished!! Assume poster axed it!!

Use as much compression as you wish. You must please yourself, not others!

Jack

[Phil Allison[_4_]]

Mike Rivers wrote:

---------------------------
>
> > ** You have completely misread my words.
> > ** That is the direct OPPOSITE of what happens !!!!
>
> > The peaks go unaltered because of the slow response of the detector
> > while lower levels are *reduced* when gain reduction finally kicks in.
>
>
> This is a studio technique, not a scientific technique. The peaks are
> unaffected by the gain reduction because we let them slip through before
> the detector knows what happened. You still have to manage the peak
> levels so they only distort as much as you want them to (I hate to have
> to say that). But when you squash what's left and then bring up the
> level, you increase the apparent loudness.
>

** Purest Gobbledegook.

Once the signal has been EXPANDED it stays like that.


>
> > ** The dbx 160 and its near relatives have NO such controls.
>
> The dbx 160 just happens to be "right" as it's built, to achieve a
> certain effect.
>


** The "effect" is called peak expansion.

The settings used are falsely described as "peak limiting" by dbx.


> They didn't plan it that way. They planned it as a more
> or less normal compressor and it works pretty well like that, but with
> certain program material, it lets the attack through and lets you boost
> the sustained part of the waveform envelope.
>

** ********.

That is just your mad fantasy.



> > Fast attack is essential to creating "peak limiting".
>
> Agreed, but I didn't think we were talking about peak limiting.
>


** My post is about so called peak limiter that in fact EXPANDS.

Try reading the thread again.




..... Phil