Compressor or Limiter??

[bigtoe]

hm...but there is limiting occuring...it's just that the initial transient is allowed to pass.

i know what yer getting at but it's just kinda off base the way i learned it which is a limiter is 10:1...no matter how much GR is being applied. the actual limiting is in the ratio beging used, not how the limiter is being applied to the program material.

kinda like saying - this isn't an eq until you boost 15K 10dB.

edit - i hear ya both. thank much for your time! i'm still unconvinced but i'm annoying myself.

glen - i have a shaved head! your hair analogies...they...confound me... it's been...oh...such a long time since i had hair.
MIke

 

[mixsit]

Yep. A limiter that lets attack transients through isn't actually "limiting" much, is it? That'd be nothing more than standard compression at high ratio.

And, yes, it is possible to use limiters with slower attack times, i.e. to basically use them as high-compression compressors. But that, by very definition, is not "limiting" so much as it's slow-clamping compression.

G.

Huh? I always thought that is exactly the generic definition of limiting; >10:1. The 'limit' setting on an LA2A for example?
Went to Rane here BTW.

http://www.rane.com/par-l.html

Just play into this fun; I recently set up a soft-plug to do 2:1, 'zero' attack, fast release to reign in some percussion. A collision in terms there.

 

[Robert D]

Huh? I always thought that is exactly the generic definition of limiting; >10:1. The 'limit' setting on an LA2A for example?
Went to Rane here BTW.

http://www.rane.com/par-l.html

Just play into this fun; I recently set up a soft-plug to do 2:1, 'zero' attack, fast release to reign in some percussion. A collision in terms there.

You have to include the second line in Rane definition. "A compressor with a fixed ratio of 10:1 or greater. The dynamic action effectively prevents the audio signal from becoming any larger than the threshold setting."

That second line is key, and speaks to the attack time.

 

[bigtoe]

"The 'limit' setting on an LA2A for example?"

uh oh...i think that one is a can of worms...unless i'm mistaken that LA2 ratio is actually program dependent. the more it compresses/limits the higher the ratio, no?



this is harder than anatomy.

see ya for the night.

 

[mixsit]

You have to include the second line in Rane definition. "A compressor with a fixed ratio of 10:1 or greater. The dynamic action effectively prevents the audio signal from becoming any larger than the threshold setting."

That second line is key, and speaks to the attack time.

Agreed, but it does not have to mean zero attack does it?

 

[Farview]

Agreed, but it does not have to mean zero attack does it?

If you don't want anything to get past the threshold, it means you have to get pretty close to zero attack.

 

[SouthSIDE Glen]

You guys are making it harder than it has to be.

Yes "limiting" is normally considered to be in the gain reduction ratio range of 10:1 or greater. but this is as applied to pretty much the whole signal.

Just think of the words being used: letting the attack transient get past the limiter before clamping down on the rest of the signal, isn't doing much of a job of "limiting" the transient, is it? Even if you have a compressor that goes to 15:1, if the first 10ms (or whatever, I'm just pulling a number out of a hat) of the signal manages to jump as high as it pleases - unimpeded before the clamp comes on - then that's not being "limited" very well, is it?

Maybe a look at the extreme may help. There's a term called "brick wall limiting", or "hard limiting". It's like building a brick wall - or actually a brick ceiling - above which no signal can pass. The signal is not cut off, there just an *extremely high* compression ratio being applied at threshold (often on the order of 40:1 or greater, all the way to infinity:1).

That kind of limiting is probably easiest to understand. It's absolute. It's a virtual brick wall. Virtually infinite compression applied to any signal wanting to jump the threshold. A signal hits the wall and goes no further.

As one starts sliding down the compression ratio scale, that "brick wall" becomes a bit softer, a bit more giving. At 10:1 it's still pretty extreme compression, but certainly not a brick wall. A 10dB transient spike above the threshold setting on the input will still show as a transient on the output, but it will be reduced to a 1dB transient. It will be able to "push the wall" one dB before the wall refuses to give any more.

The difference between a limiter and a compressor at 10:1 is usually in the speed of response time , a.k.a. attack time (limiters usually being faster and more agile there), so that it can limit the transients as efficiently as it can the rest of the signal. Additionally, hard limiting usually (but not necessarily) is accompanied by a harder knee characteristic. You hit the threshold and BANG, you hit the wall.

G.

 

[SonicAlbert]

It's also worth mentioning that digital brickwall limiters like the Waves L2 and many plugins are "look ahead" limiters, so no transients get past them at all.

 

[tkingen]

Yes "limiting" is normally considered to be in the gain reduction ratio range of 10:1 or greater. but this is as applied to pretty much the whole signal.
G.

Glen,

I'm not second guessing you but this may sound misleading to some. AFAIK, limiting isn't applied to the whole signal, but just as a ceiling to capture the peaks.
If I didn't know better I would interpret your response to say that you should set the threshold to capture everything - which would then make it extreme compression rather than limiting.
Correct me if I'm wrong - I just know what works for me.

 

[SouthSIDE Glen]

Glen,

I'm not second guessing you but this may sound misleading to some. AFAIK, limiting isn't applied to the whole signal, but just as a ceiling to capture the peaks.
If I didn't know better I would interpret your response to say that you should set the threshold to capture everything - which would then make it extreme compression rather than limiting.
Correct me if I'm wrong - I just know what works for me.

What I was referring to when I said "the entire signal" was addressing the idea of having a fast enough attack to be able to clamp the initial transients as well as it could the rest of the signal. Again, the word "limiting" - i.e. "setting a limit".

Does this mean one *has to* limit the entire signal? No, of course not. You're right about that; one can (and usually should) be limiting only the peaks, just like you say.

I was simply saying was that a limiter has to be both agile enough and tough enough to truely limit anything the signal can throw at it, and not let some of it "slip through". That's all.

For example, what good is it to set the threshold of a limiter at -0.3dBFS to block clipping if transients shoot past the threshold because the limiter's attack response is too sluggish to catch them, or because the reduction ratio isn't hard enough to keep the strongest transients from over-saturating (digital clipping)? That's not exactly "limiting" the signal very well, and it certainly isn't doing it's intended job of defending against clipping very well.

Limiting is really nothing but the extreme end of compression. But to handle those extremes, limiters spec out beyond what average compressors can do, even at the compressor's typically extreme settings.

G.

 

[bigtoe]

"Even if you have a compressor that goes to 15:1, if the first 10ms (or whatever, I'm just pulling a number out of a hat) of the signal manages to jump as high as it pleases - unimpeded before the clamp comes on - then that's not being "limited" very well, is it?"

if you have a compressor that goes to 15:1 - you no longer have a compressor, you have a limiter. if the unit being used as a limiter doesn't act fast enough for you...don't call it a compressor...call it a limiter that isn't doing what you want and go get a faster limiter.

i'm sorry - did someone like change the color of the sky out there? just kiddin'! i appreciate the words.

i understand the functionality issue...and i know there are differences between the design of some dedicated limiters and compressors with ratios of 10:1 and higher, and i know there are differences between certain kinds of limiters when you getinto the guts of em...but i guess i'll be the ol' stodge that says...limiting is 10:1 and up. period. end of story. say goodnight gracie. (until i can find some info saying otherwise or a recording god comes and knocks me on my ass. )

when you start getting into how a limiter is used or characteristics of a specific limiter...well...go on and ramble tamble as much as you want.

up until the digital age there was no way to look ahead and figure out how much a signal needed to be clamped down upon...there was always signal getting thru...and there were still limiters.

goodnight gracie. i'm going to see what scott dorsey says on rap...

edit - well about 15 second on a rap search told me this tail has been chased before a few hundred times...10:1 is somewhat arbitrary but still the accepted definition...the funtional definition is out there as well...

R.I.P.

Mike

 

[travelin travis]

imagine you're walking down a sidewalk. southside glen is standing beside the sidewalk with a hefty 2x4 ready to whack you on the head (you're the signal and glen is the limiter). you tell glen that anything coming down the sidewalk that's 5' or taller gets whacked (threshold). you tell glen that anything 10' higher than 5' gets whacked down to 1' higher than 5' (10:1 ratio). if you are 15' tall and you walk by glen, you will end up 6' tall after getting whacked. one more thing........you tell glen that he must do his whacking at a precise time (attack). glen being the nice guy that he is, honors your request. let's say you tell glen to whack at precisely 9:30 AM. glen stands by ready and waiting. you happen to stroll by at 9:29:59 AM, and did'nt get whacked. you were one second early. glen still executes his mighty whack at 9:30 AM, with enough force to squash your freakish 15' stature down to 6'. it does'nt matter though. you were one second early.

 

[RAK]

I was always under the impression that attack time was the time it took to reach full compression and release time was the time it took to "reset"

 

[SouthSIDE Glen]

My god, I can't believe how much freakin' HARDER everybody is trying to make this subject than it actually is.

There's nothing "arbitrary" about the definitions. If the circuit isn't agile enough to limit the entire signal when called upon to do so, it istn't limiting the signal. Regardless of what the ratio is set to. If I had a box that threw a 40:1 ratio at a signal, but didn't clamp until 20ms in, it'd be a high-ratio compressor, not a limiter.

And if the circuit isn't hard enough to throw high ratio reduction, even if it had a super-fast attack it'd still be just an ultra-fast compressor and not a limiter.

To limit a signal one need to truely *limit* it, meaning it's got to be able to have the agility (speed) to not let any transients sneak through, and it's got to have the strength (high compression ratio) to be able to truely throttle signals to the threshold. You gotta have both to truely "limit" the signal. Loose one or the other (via design spec or simply via knob settings), and one is no longer limiting the signal.

Just where are the lines drawn? OK that does get somewhat arbitrary. Just because a ratio is set to 9.9:1 instead of 10:1, does that mean it's not limiting the signal? Or just because the attack "only" goes as fast as 2.1ms and not 2ms, does that mean that it's not limiting the signal? A lot depends upon the nature of the signal.

But to keep it simple and general, limiting means being able to control the entire signal both in speed of response and hardness of compression. Any device that can do that to a given signal will be said to be limiting it, regardless of whether it says "compressor" or "limiter" on the front of the box.

G.

 

[bigtoe]

My god, I can't believe how much freakin' HARDER everybody is trying to make this subject than it actually is.

There's nothing "arbitrary" about the definitions. If the circuit isn't agile enough to limit the entire signal when called upon to do so, it istn't limiting the signal. Regardless of what the ratio is set to. If I had a box that threw a 40:1 ratio at a signal, but didn't clamp until 20ms in, it'd be a high-ratio compressor, not a limiter.

And if the circuit isn't hard enough to throw high ratio reduction, even if it had a super-fast attack it'd still be just an ultra-fast compressor and not a limiter.

To limit a signal one need to truely *limit* it, meaning it's got to be able to have the agility (speed) to not let any transients sneak through, and it's got to have the strength (high compression ratio) to be able to truely throttle signals to the threshold. You gotta have both to truely "limit" the signal. Loose one or the other (via design spec or simply via knob settings), and one is no longer limiting the signal.

Just where are the lines drawn? OK that does get somewhat arbitrary. Just because a ratio is set to 9.9:1 instead of 10:1, does that mean it's not limiting the signal? Or just because the attack "only" goes as fast as 2.1ms and not 2ms, does that mean that it's not limiting the signal? A lot depends upon the nature of the signal.

But to keep it simple and general, limiting means being able to control the entire signal both in speed of response and hardness of compression. Any device that can do that to a given signal will be said to be limiting it, regardless of whether it says "compressor" or "limiter" on the front of the box.

G.

not harder glen, just trying to figure out why someone was remotely bringing attack and release into limiting. to my eyes, it sounds like you are talking about 'brickwall limiting.' that's a specific type of limiting...at least that's how i learned it.

i have understood every point yer making. it's not that ya aren't being clear...

how many people have been taught limiting is 10:1 and up? raise your hands. it's common knowledge! but you know... so is not plugging a ribbon mic into phantom power...and that's a myth i once believed in before i bought a daking pre... so i asked about the 10:1 thing.

my la2 has a comp/limit switch and i can for sure tell ya - it's there due to the ratio...not the attack time.

i dunno - it's not a huge deal...but you are talking about the actual act of limiting...i can use a limiter however i want...it's still a limiter by box and by definition as a lot of us were taught and how we talk about limiting.

it's obviously a standards thing...you know what they say about standards. or a grey area thing...that's the area where there isn't skin on my head.

pax!

 

[SouthSIDE Glen]

how many people have been taught limiting is 10:1 and up? raise your hands. it's common knowledge! but you know... so is not plugging a ribbon mic into phantom power...and that's a myth i once believed in before i bought a daking pre... so i asked about the 10:1 thing.

Yeah, you're absolutely right. Theres a whole plethora of "common knowledge" that people have been "taught" that's mythological or just plain wrong (hi-fi speakers are hyped, studio monitors are flat, more louder = more better, analog is better than digital, digital is better than analog, big names mean quality engineering, mastering is where productions are made to sound professional, LDCs rule the microphone universe, etc. etc. etc.)

The whole 10:1 thing - while having a basic kernal of truth in it as far as it goes - is one of those oversimplifications that are rampant in the subject of compression, and leads to myths and other erroneous sundry.

For some reason which I never entirely understood, there is a tendancy for folks to try to simplify compression in general down to compression ratio and ignore the other parameters as minute details only.

Personally I would not consider 10:1 as a "brick wall", especially if there's a soft knee and a slow attack. Even 15:1, if you have a soft knee and slow attack, is still going to be a pretty "soft" wall, relatively speaking. And we haven't even talked about the relation of the threshold setting to the signal RMS. Once again, considering ratio alone when talking about compression is missing 85% of the equation.

i can use a limiter however i want...it's still a limiter by box and by definition as a lot of us were taught and how we talk about limiting.

Ahhh, now that starts venturing into labels versus fuzzy logic and all that stuff. Is an object defined by what it's named or by how it's used?
Is a elephant's foot that's used as an umbrella stand an elephant's foot or an umbrella stand? Or is it both? Or neither?

I was trying to avoid all that bugaboo by talking about limiting and compression instead of limiters and compressors; i.e. ignore the labels and look at the actual purpose/function. My Pro VLA is labeled a "leveling amplifier" and not a compressor. Yet nobody that has ever crossed my path has ever mistaken it for - or called it anything but - a compressor. Labels mean nothing (see "studio monitor" for another example of bad labeling and newbie myth).

Sure you can use many limiters like a standard compressor if you set the knobs so and apply the device to thie signal so. At that point you are applying compression, not limiting, even though the label on the front still says "limiter". And I give you credit for undertanding and using that flexibility in the device.

But that just makes the labels even more arbitray. Let's look at the VLA one more time as an example. It'll exceed 10:1 compression on the high end, and even has a fast attack setting at 2ms. But I don't think anybody experienced with the gear would call the VLA a "brick wall limiter".

On the other end of the spectrum, consider the famous Manley Variable Mu "Limiter/Compressor". It has a "Compress/Limit" switch on the front with the following specifications: "Compress": 1.5:1; "Limit": variable 4:1 to 20:1.

One device's "compressor" settings are another device's "limiter" settings. At least according to the labels.

I say (and yes, this is only an IMHO thang, one can disagree, but it's an HO behind which I believe there is a strong point) screw the labels, screw even the numbers (to a degree, anyway). Look at the current application of the processing to determine the semantics of limiting vs. less-than-limiting.

G.

 

[bigtoe]

excellent explanation and points glen. thank you. it does look like the 10:1 is just kinda a starting point...

"Is a elephant's foot that's used as an umbrella stand an elephant's foot or an umbrella stand? Or is it both? Or neither?"

awesome.

Mike