Limiter/Compressor Tales!

[ernstinen]

Hi Gals & Guys,

I remember in the early 90's when a friend loaned me his dbx 160x limiter/compressor. It was a revelation! I was like "Wow! Now I can really SING!"

So, a question I must've asked 100 times without an understandable answer (kinda like the difference between horsepower and torque): What's the difference? Here's my take, just from experience: Limiting is when you're actually recording tracks, and is used to keep the peaks down so that your overall level is as loud as possible (both in analog and digital --- Gotta fill up those bits, I've heard!)... Compression is used when you mix, so that the dynamic range is a bit "squashed," bringing up the softer things while still limiting the louder things. The result is an overall louder version of your uncompressed program material... Is that correct?

But since you are running your track(s) through the same circuitry, isn't it basically the same thing? Why don't they call the piece of gear a, I don't know, a Grobblemeister? Yeah, that's the ticket! (r) J. Ernst --- There, I've now registered "Grobblemeister" when I build my new limiter/compressor LOL!

The only time I regret over-limiting a track was on a stereo acoustic guitar opening to a song. I can "hear" my mistake to this day.

Any stories or comments? I'd love to hear them!

Cheers,

Ern

[waveheavy]

Truly, there is a difference between compression and limiting, they are not both the same thing.

Anything with a ratio of 10:1 or greater is considered hard limiting. Limiting is about the signal not being allowed to get any louder at the output.

[Len911]

The limiter/compressor is the same thing, same circuitry. The limiter is basically a cap, it doesn't allow the signal to cross the line, it might have an extreme effect if your signal is going to cross the line, however, if your signal doesn't get anywhere near that maximum line in the sand, it will do nothing. Compression on the other hand could be "on" all the time, depending on what the parameters are set at, mainly threshold.

Some of the terminology used in compressor speak imo is what makes them sometimes difficult to understand, like dynamic range or squashed. Squashed is probably the worst. What is a squashed sound? First of all, a compressor/limiter only works on gain or volume level. Automatically by turning the signal gain down primarily, though it might also automatically do a make-up gain, but most likely there is a manual knob for make-up gain. The best way I can think of to explain it is how you might assign samples for a sampler with various velocity layers. If you take an audio sample that you played at say a velocity of 127, and assign it to the 60 velocity layer, it technically will be squashed and sound unnatural. If you used the same sample across all velocity layers you will have no dynamic range. On the other hand, if you had a sample of a whisper and cranked the volume, or played it at a higher velocity... the opposite of squashed,lol! If you assigned the velocity samples backwards in a sampler, you wouldn't get a louder volume when you played the key with a light touch, you would get the loud, high velocity sample, played back at a lower volume, also if you really hammered the key, you would get the softest velocity sample played back at a higher volume. That's the sort of un-naturalness you want to avoid with a compressor, where your screaming is the same level as your whispers, or your whispers are louder than your screams, or maybe for creative reasons you want your whispers to sound like you are screaming,lol! You want to be able to hear the whispers, and keep the screaming from distortion, so you are actually narrowing the dynamic range for a practical purpose.

Again, compressor/limiters only adjust gain or volume automatically downward.

The various types of compressors, or circuit types, have their own characteristics in the way they work on the various parameters of volume: http://audioundone.com/types-of-compressor

The controls are fairly basic,

threshold The level the compressor kicks in
ratio The amount of signal reduction over the threshold
attack
release
make-up gain I have an API compressor that does it automatically, maintains unity gain, so there is no knob

That's how I understand it, the basic principles, anyway.

[Len911]

(kinda like the difference between horsepower and torque): What's the difference?

The Z06's LT4 supercharged 6.2L V-8 engine is SAE-certified at 650 horsepower (485 kW) at 6,400 rpm and 650 lb-ft of torque (881 Nm) at 3,600 rpm.Jun 6, 2014

In 2001 a larger stroke crankshaft increased the engine volume to 14 L (854 cu in), the power increased to 575 hp (429 kW) and torque increased to 1,850 pound force-feet (2,510 N. m). In 2007 the 12.7-liter Detroit Diesel Series 60 was discontinued.

Apparently, the horses in the first example are actually Shetland ponies, and the second example, Clydesdales?

Actually, I think torque is a component of horsepower, but so are a lot of other things.

[waveheavy]

The main thing is to be careful of how one thinks of the words compression and limiting, because they ARE... different terms and actions.

A compressor with at least a 10:1 ratio or higher can be used for limiting. Just because there's a plugin that says "Limiter" on it, or that is advertised as a "brick wall limiter", that doesn't mean to just slap it on the master bus and drive it as hard as you want. It can add distortion to your master if driven too hard.

Although leveling amplifiers like the classic UA LA2A and the compressor/limiter Fairchild 670 have no ratio knob like most compressors do, they're still called compressors, although they were mostly used as the last stage of audio processing to set the final levels.

https://www.attackmagazine.com/reviews/ ... r-made/18/

[Len911]

Although leveling amplifiers like the classic UA LA2A and the compressor/limiter Fairchild 670 have no ratio knob like most compressors do, they're still called compressors,

http://vintageking.com/fairchild-670-st ... 90-vintage

http://vintageking.com/universal-audio-la-2a

"The Fairchild 670 is a variable-mu type compressor"
"Universal Audio LA-2A is an electro-optical type classic compressor"

Because they are compressors, just not the VCA type compressor.

[mojobone]

If all compressors did the same thing in the same way, you'd only ever need one compressor, right?

[Len911]

If all compressors did the same thing in the same way, you'd only ever need one compressor, right?

I guess it depends. If they all "sounded" the same, if they were linked for a stereo signal, or if analog, as many as the channels you were recording at once? Even the same brand and model should be linked for a stereo signal.

[waveheavy]

Per your Vintage King link:

"Fairchild 670 Stereo Compressor/Limiter #490 (Vintage)"

So it's not... just a compressor only, it has historically been used as a mastering limiter also, showing that compression and limiting are two 'different' types of operations as I said before. Just so everyone knows the difference.

[mojobone]

A compressor is a tool designed to do one thing; reduce dynamic range for fun and profit. It turns out one can use a compressor for lots of other stuff, too. Mostly the stuff we use compressors for, these days are for some of the unintended consequences of using differing technologies to compress (reduce) dynamic range. I hear tell some vintage compressors get audio sent through them that doesn't even need to have the dynamics reduced; people just like the sound of the transformers.