Can someone explain to me the function of a compressor?

[cfanyc]

An automated volume controller is literally exactly what a compressor is.

The details are all in how the automation reacts to the input.

Not always. A spectral compressor for example cannot be replicated with a volume controller.
A tape machine that compresses the signal because of how the physical medium
behaves is definitely not automating some volume control.

...come to think of it, every signal generator and signal processor that exists could, in a sense, be described as an "automated volume controller" of some kind But in a very practical sense, compressors are definitely, literally, volume controls.

What an amazing conjecture. Pray tell us how the following audio processors
can be implemented as automated volume controls:

1. equalizer
2. delay
3. convolution reverb
4. odd order harmonic distortion
5. pitch correction
6. subharmonic bass generator

[BlitBit]

An automated volume controller is literally exactly what a compressor is.

The details are all in how the automation reacts to the input.

Not always. A spectral compressor for example cannot be replicated with a volume controller.
A tape machine that compresses the signal because of how the physical medium
behaves is definitely not automating some volume control.

But the effect of tape compression still looks as if someone has altered the volume of the original signal, doesn't it? What are the physical effects that cause tape compression? How do the additional harmonics appear? I guess the energy of the original harmonics somehow gets transformed into additional harmonics?

...come to think of it, every signal generator and signal processor that exists could, in a sense, be described as an "automated volume controller" of some kind But in a very practical sense, compressors are definitely, literally, volume controls.

What an amazing conjecture. Pray tell us how the following audio processors
can be implemented as automated volume controls:

1. equalizer
2. delay
3. convolution reverb
4. odd order harmonic distortion
5. pitch correction
6. subharmonic bass generator

Considering the smiley in his message I assume that foosnark did not mean it that serious.

Anyway, I think a delay is the best example for an audio processor that cannot be implemented as a volume control. Let's assume we want to implement a set delay of 1 s. If you play a transient sound that's shorter than one second and that therefore goes back to complete silence before the signal is repeated there's no way to alter the volume of the silence to form it to the delayed version of the original signal. So each effect that uses delays for it's implementation also cannot be considered as a complex automated volume control.

[foosnark]

Not always. A spectral compressor for example cannot be replicated with a volume controller.

Moving the goalposts I see... fair enough, since I added a goofy response to my post

You could still say it's a "volume control" over individual filter bands or frequency bins, etc. The same principle applies. If I were building an analog multiband compressor it would have a VCA (an automatable volume control) for every band. If I were building one in code, it would have a level multiplier (an automatable volume control) in every band.

A tape machine that compresses the signal because of how the physical medium behaves is definitely not automating some volume control.

But that's a tape machine, not "a compressor" as such. Compression is a useful side effect... but the compression it's doing is still fundamentally something that is happening to the volume.

What an amazing conjecture. Pray tell us how the following audio processors can be implemented as automated volume controls:

It's all math (or voltages, but we're talking digital here, so... it's math).

Volume control is multiplication. If you assume some non-zero base signal level to start with, you can "automate" multiplication of that value to create any signal. So a delay works via automating that multiplier based on analysis of past input...

It's farcical, but it's not untrue, and I was kind of hoping people would see both of those things It's sort of like:



Odd order harmonic distortion is nonlinear waveshaping, which is a type of algorithmically simple volume control. A level in = a level out with no time domain elements to consider.

[toonertik]

Not always. A spectral compressor for example cannot be replicated with a volume controller.

Moving the goalposts I see... fair enough, since I added a goofy response to my post

You could still say it's a "volume control" over individual filter bands or frequency bins, etc. The same principle applies. If I were building an analog multiband compressor it would have a VCA (an automatable volume control) for every band. If I were building one in code, it would have a level multiplier (an automatable volume control) in every band.

A tape machine that compresses the signal because of how the physical medium behaves is definitely not automating some volume control.

But that's a tape machine, not "a compressor" as such. Compression is a useful side effect... but the compression it's doing is still fundamentally something that is happening to the volume.

What an amazing conjecture. Pray tell us how the following audio processors can be implemented as automated volume controls:

It's all math (or voltages, but we're talking digital here, so... it's math).

Volume control is multiplication. If you assume some non-zero base signal level to start with, you can "automate" multiplication of that value to create any signal. So a delay works via automating that multiplier based on analysis of past input...

It's farcical, but it's not untrue, and I was kind of hoping people would see both of those things It's sort of like:



Odd order harmonic distortion is nonlinear waveshaping, which is a type of algorithmically simple volume control. A level in = a level out with no time domain elements to consider.

As I read through the posts, I was thinking of the answer I would post to those who didn't get your post. ... but beaten to it.

However I would like to add...
History... very useful.
Leveling amps, as they were then known, from the early broadcast days were created..
to.. yup... automatically adjust the level/volume so as not to over modulate the signal for transmission... History of gear is also useful (as well as general history of mankind's' FK_UPs... lol)
compressors just evolved from them... more controls and at around the same time some engineers found creative uses beyond the main purpose that have now become sort of defacto uses.

For example.. mid late 1970's as a live sound engineer, I had 2 DBX160.. their sole job was to sit on the mix output so as to not overdrive the PA...(automatic level limiting) very boring. It wasn't 'till I came off the road and got into studio work, that I used them and the Neve 2254s for more creative uses.

I spent my professional sound life with analog and tape... as foosnark says... tape is NOT a compressor.. compression just a side effect. Totally different thing.

As to the farcical bit... yeah, I got that... especially in the real volts environment... maths just tries to mimic that...
wiggle air... like that

To understand compressors... a look at the history can be useful..

[cfanyc]

So to summarize your argument, compression is volume control
but volume control is multiplication and since multiplication
is in many math operations, which is the basis of audio processing
every audio processing is volume control (and equivalently compression).

And lets not forget the following: all complex math involves multiplication, and audio processing
is complex math and compression is audio processing hence multiplication
is compression and since volume control is multiplication which is compression,
then compression is also volume control.

Thanks for enlightening us!

[foosnark]

Glad I could clear it up

[Reverend Rhythm]

I'm wondering if this video and FabFilter Pro-C 2 might be, by it's self a good way to learn compression? I think the graphics would be useful in seeing what is happening.

It doesn't get better than Dan Worrall.
https://www.youtube.com/watch?v=BIVfpsoPnOo

I'm wondering if this video and FabFilter Pro-C 2 might be, by it's self a good way to learn compression?

[jochicago]

I found the short version of the answer to OP's question:
https://patches.zone/compression-guide

Also, a fun tool to visualize what's happening with the settings
https://codepen.io/animalsnacks/pen/VRweeb

[klaatugort]

it turns this:n into this:N

[Mushy Mushy]

it turns this:n into this:N

Not entirely true. It turns N into n. It’s called compression after all

[bazwillrun]

@jochicago I only have these compressors to my availablility (It are a few of the the plugins that are available in the all acces pass): https://www.slatedigital.com/virtual-analog-bundle/

Wow, you have the complete Slate bundle, and you don't know what a compressor is?

Just arrived from the n-dimension with your ma's credit card?

sounds like a classic "all the gear, no idea"

[DJ Warmonger]

So to summarize your argument, compression is volume control
but volume control is multiplication and since multiplication
is in many math operations, which is the basis of audio processing
every audio processing is volume control (and equivalently compression).

And lets not forget the following: all complex math involves multiplication, and audio processing
is complex math and compression is audio processing hence multiplication
is compression and since volume control is multiplication which is compression,
then compression is also volume control.

Thanks for enlightening us!

Warning, we have internet expert here! He will not rest until he proves he's right!

[jethrobull]

The burning question in my mind is, are things any clearer now Mozex?

[fmr]

The burning question in my mind is, are things any clearer now Mozex?

After the "math" discussion, and whether everything is or isn't volume automation? I sincerely doubt it.

[el-bo (formerly ebow)]

The burning question in my mind is, are things any clearer now Mozex?

He really would’ve been better off Poogling it