## Difference between soft-clippers and compressors?

lenieNt Force
KVRist

71 posts since 17 May, 2007
What is the difference between a soft-clipper and a compressor? Never heard much talk about soft-clippers and what they do, but what I've learned lately is that they can be very handy. I know they're not like limiters, but more like compressors in functionality by rounding off the peaks instead of making squares.
aciddose
KVRAF

11863 posts since 7 Dec, 2004
there is no difference, a compressor or limiter is just variable automatically by a linear filter applied to the control signal.

it's similar to the difference between a eq, a filter and an auto-wah.

ultimately effects are divided into two categories, linear effects like filters that change the amplitude and phase of a signal in a constant and continuous way, and non-linear effects that change the amplitude and phase differently depending upon the input amplitude/phase.

a compressor is really a combination of non-linear filters controlling linear filters controlling linear filters which makes the system as a whole non-linear.

n = linear
n*n = nonlinear

in a clipper you have a similar situation, the main difference being that rather than frequency filters controlling amplitude filters, we have amplitude filters controlling amplitude filters.

so a compressor is like:

output = input * follower <-- linear filter (although, since the control is derived from the input, it's the same as input*input making it non-linear)
control signal = 1 - abs(output) * 1.0/threshold <-- nonlinear filter
follower = envelopefilter(control signal) <-- linear filter (it's actually non-linear if there are separate attack/release)
hardclip(follower) <-- nonlinear filter

while a soft-clipper is like:

control = 2 - abs(input) <-- non-linear filter
parabolic = input * control <-- linear filter (although, since the control is derived from the input, it's the same as input*input making it non-linear)
output = hardclip(parabolic) <-- non-linear filter

so, you can see hopefully that once there is any non-linear element in the chain it makes the system as a whole non-linear.
Music Engineer
KVRAF

3757 posts since 8 Mar, 2004, from Berlin, Germany
the difference is that a (soft) clipper simply applies a waveshaping function (a function, mapping the instantaneous input to instantaneous output) whereas a compressor (or limiter) analyzes the amplitude envelope of the input signal and applies a gain factor derived from that. that amplitude envelope tracking is inherently a dynamic/time-varying process, whereas waveshaping deals only with instantaneous signal values
lenieNt Force
KVRist

71 posts since 17 May, 2007
@aciddose

hardclip(parabolic) <-- Does this confirm my statement on the soft-clippers round off the peaks instead of making square waves like a limiter?

If there is no difference between compressors and soft-clippers, why do we have soft-clippers?

Is the only difference that compressors have more controllable parameters, like knee, attack and release to control the shape, while soft-clippers just make a constant parabolic shape on the peaks?
Music Engineer
KVRAF

3757 posts since 8 Mar, 2004, from Berlin, Germany
...but one may view a (soft) clipper as an extreme case of a (softknee) limiter, namely one with instantaneous (zero) attack- and release- time constants
lenieNt Force
KVRist

71 posts since 17 May, 2007
Robin from www.rs-met.com wrote:the difference is that a (soft) clipper simply applies a waveshaping function (a function, mapping the instantaneous input to instantaneous output) whereas a compressor (or limiter) analyzes the amplitude envelope of the input signal and applies a gain factor derived from that. that amplitude envelope tracking is inherently a dynamic/time-varying process, whereas waveshaping deals only with instantaneous signal values

Yea, thanks. Confirmed my last post I guess.
Music Engineer
KVRAF

3757 posts since 8 Mar, 2004, from Berlin, Germany
lenieNt Force wrote:@aciddose

If there is no difference between compressors and soft-clippers, why do we have soft-clippers?

i think, aciddose boiled it down to the question of linear/non-linear. it is true that both are non-linear, but that does not render them equal. there's a whole multitude of nonlinear effects.....
Kim Lajoie
KVRAF

4692 posts since 28 Jan, 2003, from In these very interwebs
Oh, for crying out loud...

Limiting is a (high-ratio, fast attack) special case of compression. It'.s not meant to make square waves. If it does, it's doing it wrong (or it's more than just a limiter). Both limiting and compression work by applying gain reduction (volume control)

Soft clipping is a (gradual transition) variation on hard clipping. Where hard clipping goes from clean to full clipping instantaneously, soft clipping has a gradual transition from clean to full clipping. Both hard clipping and soft clipping work by applying waveshaping (distortion).

More background on limiting vs clipping here.

-Kim.
bmanic
KVRAF

7954 posts since 3 Feb, 2003, from Finland, Espoo
Yes but like aciddose kind of said, a clipper is a limiter with instantaneous attack and release. There really is not much more difference than this. We add attack and release to control the amount of distortion with the side effect of shaping the transient and the information that follows it (release stage decides how large a chunk of information, that follows the initial transient, is changed).

A clipper is basically more transparent than a limiter provided that we only clip a very short bit at a time and not all the time (to minimize distortion and thus fatigue). The DA converter can not of course reproduce a square wave which means it'll come out of your system less damaged than one would perhaps think. This is why clippers are perceived as transparent, keeping the original transient information as it is, but instead add annoying distortion.

So, it's a trade off, at least in a mastering situation.

Edit: well Kim's link basically gets to the same conclusion I see. I knew I should have read it first.. my bad.

Cheers!
bManic
"I'm not trying to be anyone's savior. I'm just trying to think about the future and not be sad." - Elon Musk, TED talk April 2017
eduardo_b
KVRAF

11914 posts since 22 Nov, 2004, from west of east
Kim (esoundz) wrote:Oh, for crying out loud...
We escape the trap of our own subjectivity by
perceiving neither black nor white but shades of grey
eduardo_b
KVRAF

11914 posts since 22 Nov, 2004, from west of east
Kim (esoundz) wrote:Soft clipping is a (gradual transition) variation on hard clipping.
Favorite clippers -- hard, soft, ambivalent?
We escape the trap of our own subjectivity by
perceiving neither black nor white but shades of grey
Kim Lajoie
KVRAF

4692 posts since 28 Jan, 2003, from In these very interwebs
eduardo_b wrote:
Kim (esoundz) wrote:Oh, for crying out loud...

I just thought that someone who doesn't know the difference between a clipper and a compressor is someone who doesn't understand some fundamentals about dynamics processing. And the first response goes into algorithmic detail about the difference between linear transfer functions and non-linear transfer functions, and why linear filters become non-linear filters when controlled by non-linear filters.

And then the second response is about functions that map instantaneous input to instantaneous output.

This for a person who doesn't understand why a compressor isn't a clipper.

-Kim.
Kim Lajoie
KVRAF

4692 posts since 28 Jan, 2003, from In these very interwebs
eduardo_b wrote:
Kim (esoundz) wrote:Soft clipping is a (gradual transition) variation on hard clipping.
Favorite clippers -- hard, soft, ambivalent?

I prefer hard clippers.

The trade-off with soft clippers is that the clipping isn't as hard-edged, but the clipping starts earlier. For small amounts of clipping, hard clipping is more transparent because it's changing the audio less of the time. For large amount of clipping, hard clipping emphasises the distortion that's already there (if you're applying that much clipping, you'd better be clipping an already-distorted signal) by focussing the energy in the upper frequencies. To my ears, large amounts of soft clipping seems to damage the mids more than hard clipping.

-Kim.
BobSlot
KVRer

8 posts since 10 Jul, 2009
I think a lot of info here is way above the normal people's head, but Wikipedia explains it good imo:
http://en.wikipedia.org/wiki/Dynamic_range_compression

There is also a picture to show what is the difference of limiter (it is really just a compressor with hard settings) and clipper:

The sum is what someone already said that a clipper is a compressor with instant attack and instant release, and a soft clipper can be compared to a soft knee compressor with instant attack and release.

This is my definition of what it is anyway.

Edit: Kim's message has also explained it good.
eduardo_b
KVRAF

11914 posts since 22 Nov, 2004, from west of east
Kim (esoundz) wrote:
eduardo_b wrote:
Kim (esoundz) wrote:Soft clipping is a (gradual transition) variation on hard clipping.
Favorite clippers -- hard, soft, ambivalent?

I prefer hard clippers.

The trade-off with soft clippers is that the clipping isn't as hard-edged, but the clipping starts earlier. For small amounts of clipping, hard clipping is more transparent because it's changing the audio less of the time. For large amount of clipping, hard clipping emphasises the distortion that's already there (if you're applying that much clipping, you'd better be clipping an already-distorted signal) by focussing the energy in the upper frequencies. To my ears, large amounts of soft clipping seems to damage the mids more than hard clipping.

-Kim.
Okay...thanks for that...but I was also wondering which ones, in particular, are used by the Kimster.
We escape the trap of our own subjectivity by
perceiving neither black nor white but shades of grey
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