Hey, so I tweak a compressor by ear and usually don't pay attention to the numbers on the screen but I've seen some compressor plugins letting you choose ratios like 4:0, 2:0 and such, like the FET compressor from Softube. So If the compressor says 4:1 ratio, it means that, for every 4 db crossing the threshold, 3 db would be compressed and 1db would be allowed to pass through. So if the ratio is 4:0, for every 4 db, does it mean no signal would be allowed to pass through ? essentially limiting the signal if it never passed 4db ?
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https://iconcollective.edu/audio-compressor-ratio-explained/

This should explain everything.

 

No not strictly true.

You have to take into account attack times which mean some of the signal can pass the compressor untouched (& won't be reduced).

Also, ratios on vintage gear (& their emulated plugins) are approximate values & vary from 1 comp to another.

Ratio amounts can also vary depending on the amount of reduction happening. Heavier amounts of compression can have a different effect.

The speed of the reduction is also a factor to consider as some compressors aren't all reducing the level at the same rate. Some slower compressors might not even reach the set ratio amount before it starts to trigger it's release stage. This can lead to all sorts of inconsistencies in level control (aka known as mojo...)

Some compressors also adjust their knee amount based on the ratio setting, so again another factor to consider the amount of gain reduction being applied.

Simple answer to your question is NO...

 

If the compression ratio is set for let's say 4:1, the input signal will have to cross the threshold by 4 dB for the output level to increase by 1dB.

 

I think I might not have been clear with my question. My question 4:1 or 5:2 is easy to understand. But 4:0 or 5:0? meaning Zero Dbs passing through? My question is what does zero stand for?. I understand the attack, release and knee settingz affecting the output but zero?

 

Hey, thank you. That is the general definition of what compression ratios are on most websites. But they all give examples that are easy to understand like, 4:1 or 2:1 or any number :1 (n:1). My question is strictly about what (n:0) means. ("any number : 0") Like the ones on the softube FET compressor.

 

I think it's just a weird (or more precise) way of showing the ratio that this compressor have. On the GUI graduation it show the n:1 but on the top indication (next to the preset line) it show the precise ratio number like 4.0, 2.6 or whatever you put your knob on, but without the :1, so it can seems a bit confuse and look like a 4.0 or 2.6 ratio when it should say 4.0:1 or 2.6:1

 

FET Compressor is based on the 1176 Compressor where things are a bit different.

The 1176 has a fixed threshold which you have to drive the input into to get compression going. In 1176 eumlations the threshold and ratio s interact. Changing the ratio actually chnges the threshold as well which changes the amount of gain readuction to someting rather unexpected. For example 2:1 in 1176 world reduces the gain more than 4:1 since the threshold in 2:1 is lower than at 4:1. You can test this for yourself.

Any number "n" must be > 0, because otherwise 0:1 equals 0. Any what would that mean in regards to the audio signal?

 

5:2 doesn't exist. do you mean 2.5:1 ?
There is no 4:0 either. the denominator is always 1.

Edit:
if you want to limit your signal with a compressor, i recommend fast attack/release times and a ratio >10:1.

 

Last edited: Jan 27, 2021

4:1 means for every 4dB above the threshold, the output is increased by 1dB. If the input is 8dB above, this would result in 2dB higher output - if the attack time would be 0ms.

Any number:0 (like 4:0) is mathematically not allowed, even if this would be the behaviour of a brickwall limiter (infinitely input above threshold results in no increase of the output). So as soon as any signal reaches the limiter's threshold it's stopped there, 0dB added to the output.

If you think a few moments about this, you'll realize that's it's not so difficult to understand (not meant offending in any way).

 

Totally understand. I'm someone who's really comfortable with compressors. But the numbers on this softube fet compressor is making me a little dizzy. N:0 is mathematically wrong but this compressor gives the option to do so and provides no information about it anywhere in its manual. That's what is messing my head up.

 

A display bug? I can't see it here, but it's an old version (old vid)