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Can someone explain this to me?
Lets say you have 2 signals, both peaking at -6 db and going to the master channel, which has a limiter which is set on -6 db as well. One signal is very low frequencies, say 40 - 200 hertz (perhaps a sub bassline), while the other signal is 200-2000 hertz (say a mid bass). Now obviously they are both compressed when you send the signals to the master, but what does that compression look like?
Is the signal on the master now like a glass of water, half full with the very low frequencies and half full with the mid frequencies or does it not fill up at all? And which signal will make the limiter compress them first if both are sent at the same time or does it not matter?
I apologize if these questions seem simple but I just cant seem to wrap my brain around this.
The sound that hits the limiter first will cause the compression of the entire mix, followed by the rest of the sounds. Look at the attack and velocity of the signal to figure out which one is enabling the compression first. And no its not spread 50/50, the compression is spread by volume and energy. Typically your lower end sound will see the most comprsesion, because they have the most energy triggering compression, the higher frequncies sounds will see the least compression on a master bus. Sounds that have most of its volume in the higher frequencies can have lower raw volume, but due to their frequencies are perceivably louder.
So when you staging gains, have higher frequency sounds lesser in volume than lower frequency sounds when mixing relative volumes. Higher frequencies are more potent towards audible/perceivable volume, so less is volume is required for it to make it through the mix. And then also, sometimes sounds that have amplitude in a very short frequency range should be watched, because of the concentration in volume in that area, whether high or low frequencies.
If the two sounds are at the same volume and sent at the exact same time, they will both cause the compressor to act. It's kind of misleading to even consider them as separate signals at that point, because if they are mixed together then the amplitude of the combined signal will probably be greater than either of the original amplitudes considered separately, because the sounds will share frequencies to some extent, unless you are talking about pure sine waves or highly EQ'd or filtered sounds.
Kismet is on point when he talks about higher frequencies not needing as much volume to be perceived clearly.
Thanks guys, its much clearer now.
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| Originally posted by MrJiveBoJingles If the two sounds are at the same volume and sent at the exact same time, they will both cause the compressor to act. It's kind of misleading to even consider them as separate signals at that point, because if they are mixed together then the amplitude of the combined signal will probably be greater than either of the original amplitudes considered separately, because the sounds will share frequencies to some extent, unless you are talking about pure sine waves or highly EQ'd or filtered sounds. Kismet is on point when he talks about higher frequencies not needing as much volume to be perceived clearly. |
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| Originally posted by Kismet7 As long as the two sounds are not summed together into the same channel, and are seperate signals, having their own transient and dynamics, they will impart their own dynamics towards the compression. |
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| Some of the compression will be shared, but like I said one signal will trigger the threshold more than the other, and that will likely be the lower frequency sound with higher amplitude in a smaller range of frequencies. |
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| And then you have to realise due to the differences in frequencies they likely have different transient lengths, which will also affect the compression/limiting differently. Just because they are both at -6db in volume does not necessarily mean they will cause the same amount of limiting. |
yup
- 6dBfs is an amplitude level. It doesn't matter where the frequency lies. It will trigger a compressor just as much as -6dBfs at 4 kHz. And as Mr jive Bojangles mentioned, the summing is done before the insert effect so it really is just one combined signal.
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| Originally posted by MrJiveBoJingles The guy was talking about compression on the master, though, which means both tracks being sent to the same channel. He already specified he was talking about two sounds with the same amplitude, not a (measurably) loud low one and a softer high one. The way I read the guy, he was talking about two sounds that are the same in every way (amplitude, transient shape, etc.) except frequency range. Is that not how you read it? |
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| Originally posted by Kismet7 He did not say both channels are within the same channel at all, he just said both are getting limited through the master bus. |
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| The volume is just one piece of the compression, the transient affects the attack and release, and if two different sounds are hitting a compressor they will add their own dynamics to the final sound, definately not a uniform amount of compression even with the same amplitude. |
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| Originally posted by MrJiveBoJingles He said they were sent to the "master channel." I think by that he meant that the signal is summed in the master channel and then goes through the limiter. How do you read it? Of course the transient shape will affect things, but I thought the guy was talking about two sounds that were the same in everything but frequency range, meaning same transient shape, amplitude, and so on. |
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| Originally posted by Kismet7 Normally people do not be send only 2 summed tracks to the master channel alone. He would have a limiter on the master channel that would affect the entire mix, all channels. He used 2 channels as an example, and they are likely two seperate channels/signals. Unless he is a magician that does everything through 2 channels when dozens of channels are possible. And why limit just 2 channels, why not just compress instead? Simple logic and qualitative reasoning here man. And there is little chance that the two sounds are the same transient, it is safer to assume that they are not. |
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| Originally posted by MrJiveBoJingles But I didn't think he was talking about a "normal" mix, just sending two tracks to the master channel. Pretty sure he was making up a simple example for ease of discussion about compression basics, not talking about handling an entire mixed track. |
Maybe we can stop talking about this until he clarifies what he meant.

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| Originally posted by MrJiveBoJingles Maybe we can stop talking about this until he clarifies what he meant. |
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| Originally posted by Kismet7 Dude, even if he says he sent two tracks summed to a limiter, The different transients would cause different amounts of compression between the two sounds |
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| Originally posted by Kismet7 RichieV keep trying, defo need moar practice |
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| Lets say you have 2 signals, both peaking at -6 db and going to the master channel |
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| Originally posted by MrJiveBoJingles Don't accuse me of being ignorant when this argument just comes down to a difference of interpretation. |
Good thread though, making me think more about frequencies, transients, and gain staging some more.
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| Originally posted by MrJiveBoJingles But he never said they had different transients, either. Don't accuse me of being ignorant when this argument just comes down to a difference of interpretation. |
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| Originally posted by Kismet7 Logic would say they are different. They are two different frequency ranges, how could you by default assume they have the same transient? One is slower one is faster...thats is what the frequency blatantly tells you. |
Kismet fails...once again. 
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| Originally posted by MrJiveBoJingles Transient refers to the shape of the amplitude over time, not the frequency content of the sound. You can easily have a high sound with a slow transient or a low sound with a fast one. |
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| Originally posted by Kismet7 So your idea that as long as they are the same amplitude = equal compression = wrong, given that the transients will also affect the compression, and 99.99999% chance they are different, which makes you about 99.99999% wrong |
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| Originally posted by Kismet7 This is true, but to assume that two sounds have the same exact transient is ridiculous. The chances that they dont have the same transient are far greater than having the same. Even a 1 ms or two between the two sounds would impart their own dynamics when compressed on a bus/master. So your idea that as long as they are the same amplitude = equal compression = wrong, given that the transients will also affect the compression, and 99.99999% chance they are different, which makes you about 99.99999% wrong |
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| Originally posted by MrJiveBoJingles I already stated I was assuming that they had the same transient, for simplicity's sake. It's not likely to happen in the real world, but I was treating the example in as simple way as possible for the sake of helping the guy figure out the basics. |
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| Originally posted by RichieV you obviously understand very little on how a compressor works. The gain reduction isn't immediate, it doesn't happen in 1 ms. It takes an average over a number of samples which allows the lower frequencies ample time to reach maximum amplitude. You need to learn some fucking manners. |
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