Why are they called compressor/limiters?

[rcook349]

I'm learning about compressor/limiters and it looks like it's compression until you reach a really high ration (maybe 100:1) and from then on up its called limiting?

I don't understand.. seems to me it would just all be called compression and once in the high range it would just be a lot of compression.

Can someone please clear this confusion up for me?

Thanks,
Ron

[shanabit]

Dynamic range compression - Wikipedia, the free encyclopedia

Limiting - Wikipedia, the free encyclopedia


*A compressor is an amplifier whose output level decreases as its input level increases. Compressors keep the sound above the inherent noise level and below its saturation point while preserving the relative dynamics of quiet to loud. The compressor also affects the low volume signal by bringing it up above the noise floor. Think of it as squashing the high volume level and raising up the low volume level at the same time.

*A limiter is a compressor whose output level stays below a preset point regardless of its input level. Limiter usually has a compression ratio of 10 to 1 or greater. It puts a ceiling on the max loudness of a sound at a preset level. It doesnt bring up the low volume signal.

[vernier]

seems to me it would just all be called compression and once in the high range it would just be a lot of compression.

I've thought the same.

[norman_nomad]

Originally Posted by shanabit

Dynamic range compression - Wikipedia, the free encyclopedia

Limiting - Wikipedia, the free encyclopedia


*A compressor is an amplifier whose output level decreases as its input level increases. Compressors keep the sound above the inherent noise level and below its saturation point while preserving the relative dynamics of quiet to loud. The compressor also affects the low volume signal by bringing it up above the noise floor. Think of it as squashing the high volume level and raising up the low volume level at the same time.

*A limiter is a compressor whose output level stays below a preset point regardless of its input level. Limiter usually has a compression ratio of 10 to 1 or greater. It puts a ceiling on the max loudness of a sound at a preset level. It doesnt bring up the low volume signal.

This definition doesn't really make sense to me because in both cases the operative factor is the threshold.

The definition that a compressor is something that "squashes the high volume and raises the low volume" can also be applied to a limiter if, in both cases, the audio has exceeded the threshold. A compressor only "raises the low volume" by virtue of the fact that it is limiting the amplitude of the high volume thus decreasing the ratio between the low amplitude and the high amplitude. A limiter does the same thing.

I think ratio is what best differentiates a compressor from a limiter. I don't know if there's any agreed upon standard, but usually anything 8:1 or higher is considered a limiter.

[Chaellus]

compression starts form 1.5 to 1 and ends at 3:91 to 1 Limiting though thought to start at 10 to 1 actualy and trully starts at 4:1 ratio

[tenchijin2]

Compression and limiting are the same thing. But you 'limit' in order to prevent a sound from getting above a certain point as much as possible. You 'compress' to restrict its dynamic range for any number of purposes.

Don't get hung up on it.

[shanabit]

Originally Posted by tenchijin2

Compression and limiting are the same thing. But you 'limit' in order to prevent a sound from getting above a certain point as much as possible. You 'compress' to restrict its dynamic range for any number of purposes.

Don't get hung up on it.

Well said

[vernier]

When pushing the 20:1 button in ..."roger, switching to limiting mode ..limiting mode now on".

[Geoff_T]

Hi

Well, at Neve we called them limiter-compressors!

Mainly because the unit did both functions, either individually or at the same time.

[u b k]

shanabit,

your understanding of compression is in the ballpark, you're just a bit out in left field. to clear things up:

Originally Posted by shanabit

*A compressor is an amplifier whose output level decreases as its input level increases.

close, but not quite. the output level increases along with the input level, it just does so at a different rate. at a 2:1 ratio, once amplitude exceeds the threshold, every 2db of increase on input results in a 1db increase on output.

what you are describing is commonly known as 'negative compression' or 'overcompression', where the ratio is a negative one. so at 1:-2, every 1db of increase on input results in a 2db *decrease* on output. negative compression is a very cool effect, but it's also a different animal than standard compression.

Originally Posted by shanabit

Compressors keep the sound above the inherent noise level and below its saturation point while preserving the relative dynamics of quiet to loud.

to be honest, i don't know what 'inherent noise level' and 'saturation point' are, or what they have to do with compression, but i do know that compression does NOT preserve the relative dynamics of quiet to loud, it changes them. that's the whole point of compression: to change the relationship of the soft to the loud.

Originally Posted by shanabit

The compressor also affects the low volume signal by bringing it up above the noise floor. Think of it as squashing the high volume level and raising up the low volume level at the same time.

compression doesn't actually do anything to the low level sound, if we define low level sound as 'sound below the threshold'. if you want to bring up the quiet stuff, you have to apply gain after the fact, aka 'makeup gain'. most of us do this, and most compressors have a makeup gain circuit, but this is not compression.


gregoire
del
ubk
.

[psycho_monkey]

Originally Posted by shanabit

The compressor also affects the low volume signal by bringing it up above the noise floor.

That's quite a confusing statement for the newbie - it should clarify that the noise floor referred to is external to the signal being processed. Of course, compressing any signal will bring up the background noise present in the original recording, not make it less audible.

[tarnationsauce]

Some compressors have brick wall limiters after the compressor.

Also, some compressors do not have high enough ratio to be called a limiter.

[Kiwiburger]

It's just words. I like to think of Limiting as being a subset of Compression.

IMO it's not just ratio > 10:1 that defines limiting.
I believe you need a fast attack and fast release - otherwise I would call it Levelling or Automatic Gain Control or something other than limiting.
I also believe we need a high Threshold, so we are just limiting the peaks, otherwise it really is just Strong Compression.


To my mind, a good compressor can limit, but a good limiter may not be able to compress.

And I think it's important to realise that neither limiting nor compression raises the level of any signal. Both limiting and compression bring parts of a signal down.

However - most limiters and compressors are followed by a Make Up Gain amp stage, and it's this amp stage that brings the signal up. And it does this equally to both loud and soft parts. The end result may appear to be that the soft parts are raised - but it should always be understood how this is achieved. The action is always on the louder parts - and that's where the damage can occur.