Compressor confusion

S

singlespeak

New member
Hi,

Been a while.
I'm confused with Logic 8's compressor. It says in the manual that it's a downward compressor ("the compressor works by reducing levels"). Yet, I have a vocal track, it's rubbish because it's too quiet, and when I put a compressor on it (3.1:1, -6,5db, 0 db gain) my vocal track is significantly louder. I know there's such a thing as upward compression but I specifically consulted the manual to verify whether that's what's going on, and apparently it isn't.

Am I missing something?

Tnx.
 
Are you adjusting the track level to make up for the loss of the peak level? If so, that'll raise your average level just as much as make up gain on the output will.

G.
 
That compressor probably has automatic makeup gain. The more you lower the threshold, the more it raises the output. Without that, the compressor would make things quieter by the amount of reduction the compressor is doing and you would normally add some makeup gain to bring it back up. This just tries to do that for you.
 
@SouthSIDE Glen: no matter what my track level is, when I turn on the compressor the sound gets louder, when I turn it off it gets quieter. It even does so with the threshold set at 0db, in which case I expect a compressor to do diddly squat - unless the sound passes 0db which it clearly doesn't.

@Farview: What you say is very true: the more I lower the threshold, the more it raises the output. But it's a downward compressor, so as I understood it, the more I lower the threshold, the more the output should be lowered, no?
I mean, that's how it's explained everywhere, even in the manual, but I guess you're right about "automatic makeup gain", even though there's a slider for makeup gain, which I set to 0db. Maybe that's the issue? Maybe 0db for makeup gain is not the same as "no makeup gain"?

Tnx for the responses.
 
The fact that it's a "downward" compressor does not matter if it's got automatic gain compensation, which it sounds like it does. With the AGC, it will indeed make things louder the more compression you apply. That's not the compression itself doing that, its the automatic gain compensation doing it.

The output gain control that you have set to 0 comes into it *after* the automatic gain already does it's thing; meaning in your case that it's not adding or taking away anything extra after the automatic gain has done it's thing.

If there's no way to turn the automatic gain section on/off, you can use that output gain turned down to un-compensate for the automatic compensation. or better yet, just get yourself another compressor plug that works more "normally". There are lots of free ones out there that you can use if you don't want to spend the money, and lots of even better ones if you do want to spend the money.

G.
 
You are only getting confused because that particular plugin is doing the gain makeup automatically. If it didn't have that feature, the compressor would work the way you think. It is turning down the signal by the amount that the reduction meter says it is, but then it turns the signal back up to compensate. It does this in a very non-intelegent way, by just adding some gain initially and adding more and more as you lower the threshold.

If it gives you too much makeup gain, just lower the makeup gain slider. Don't get too hung up on what the numbers on any of the controls say. Just make it sound good.
 
Staying with compressors but changing topic slightly....

I believe it was Glen, and I could be wrong, that was talking about compressing in layers for mastering. Each time using corrective EQ, if necessary to scultp the final mix. That was a brilliant idea that for some reason I had never really thought of my own, and made perfect sense to me if it wasn't for the fact that I (thought) I had learned that compression was exponential....what I mean;

If you were to compress a track at 3:1, 2:1 and 4:1, that doesn't give you 7:1 compresssion ratio.....it would give you 24:1 compression. Am I off base or is that pretty much the correct way of thinking? Sorry to hijack.
 
showstone said:
If you were to compress a track at 3:1, 2:1 and 4:1, that doesn't give you 7:1 compresssion ratio.....it would give you 24:1 compression. Am I off base or is that pretty much the correct way of thinking? Sorry to hijack.
Click to expand...
Sort of. The thing is, with high ratios, you don't normally have the threshold set as low as you would with low ratios. In other words, you can compress something at 4:1 but only be 1 db into the reduction. You can also compress at 2:1 and be 6db into the reduction. So you would have to add up how much the level was actually reduced and do the math to find the ratio.

Much of the time, when doing multiple compression passes you would have the compressor set differently each time to perform a specific function. That is another reason why it will sometimes work better than one compression pass.
 
showstone said:
If you were to compress a track at 3:1, 2:1 and 4:1, that doesn't give you 7:1 compresssion ratio.....it would give you 24:1 compression. Am I off base or is that pretty much the correct way of thinking? Sorry to hijack.
Click to expand...
Farview's answer was on the nose. Just to add to it, when compressing in steps, the steps are usually quite small (for me anyway). The chances that I would pile on that much compression in three steps would be extremely small, unless, as Farview stated, the threshold were set really high just to knock down peaks, and when knocking down peaks, there really isn't much need to do it in steps.

Maybe one might go to >2:1 at a higher threshold to tame the peak dynamics, but any subsequent steps to the "body" of the signal at lower threshold might be more on the order of the 1.x:1 - 2.x:1 range each. You could have (just for illustration, not as recommendation) four steps of 1.2:1 each, and the total compression out of all of that would equal only about 2:1, and that only counts if the threshold was the same for all four steps.

But combine that multi-step 2:1 to the body with the 2:1 or more originally made to just the peaks, and you can wind up with a fairly compacted signal, and one of quite a different nature than if you just crushed the whole thing in one big bite.

G.
 
Is there a specific class of sounds for which this compression in series would be used? For example, would you do it more for vocals, or gits, or drums, etc.? Or is it just a matter of trying it out and seeing if it works on that particular recording?

Just riding the hijack.
 
singlespeak said:
Is there a specific class of sounds for which this compression in series would be used? For example, would you do it more for vocals, or gits, or drums, etc.? Or is it just a matter of trying it out and seeing if it works on that particular recording?

Just riding the hijack.
Click to expand...
Sticking you thumb out, eh? :D

This was brought up originally in a discussion of part of the process of mastering the entire stereo mix. For me, it's very unusual that I'd make multiple compression passes on a single instrument track. Oh, sometimes I might limit the peaks on a track and lightly compress (or parallel compress) the body of the track, but I don't think I personally have ever done more than that on a single instrument track.

The idea of multiple compression steps was offered as an alternative to just taking a mixdown and throwing it against a brick wall in one big step as part of a mastering job, not necessarily as a process for individual tracks during mixing.

G.
 
I guess it would depend on what you were after.
I have read that vocals are often compressed multiple times on the records you hear today. Maybe on the way in as the vocal is recorded to get the flavor and texture of particular compressor. Compressed again in the mixing process to sit in the mix and then again as a part of the whole mix through the mix bus compressor on the masterbus.

This kind of thing would mean you have some hardware comps that you want to use to add flavor in the recording process and that you have desire to use a mixbus compressor on the mix.

The best way to see if you like the sound would be to try it

No hard and fast rules and of course YMMV
 
singlespeak said:
I'm confused with Logic 8's compressor. It says in the manual that it's a downward compressor ("the compressor works by reducing levels"). Yet, I have a vocal track, it's rubbish because it's too quiet, and when I put a compressor on it (3.1:1, -6,5db, 0 db gain) my vocal track is significantly louder.
Click to expand...

Let's back up a bit. If your vocal track is too quiet, there is a very high chance that your "everything else" is too loud. You should not have to compress to hear the vocal in the first place. Start your mix over with everything else low enough that you can hear the vocal on its own.

Second, everybody is correct that your compressor has automatic makeup gain. I suggest you find a way to disable that makeup gain or use a different compressor. Auto makeup gain makes it impossible to judge if the compressor is actually helping. The glaring volume change totally overshadows the relatively subtle compression sound.
 
This story just keeps going, screw Logic's built-in compressor. I have a good vocal with one syllable being too loud. So my meter is doing fine until that one sound passes and it goes in the red. So I think, just compress that stuff! So I added a compressor and I was fiddling about with the controls and at one point I noticed that when I increase the ratio from 3:1 to 15:1, the volume actually peaks higher!
This makes no sense to me. 3:1 means that for every 3 dB over the threshold, output is 1 dB over threshold. Infinity:1 is pretty much a limiter. So how on earth can increasing the ratio actually make the overall gain louder?
Does anyone know this?
 
singlespeak said:
This story just keeps going, screw Logic's built-in compressor. I have a good vocal with one syllable being too loud. So my meter is doing fine until that one sound passes and it goes in the red. So I think, just compress that stuff! So I added a compressor and I was fiddling about with the controls and at one point I noticed that when I increase the ratio from 3:1 to 15:1, the volume actually peaks higher!
This makes no sense to me. 3:1 means that for every 3 dB over the threshold, output is 1 dB over threshold. Infinity:1 is pretty much a limiter. So how on earth can increasing the ratio actually make the overall gain louder?
Does anyone know this?
Click to expand...

I could have sworn about 5 people told you it's the auto-make up gain. It's AUTOMATIC. It doesn't matter where you have your Make-up gain slider set. :eek:

But on another note. If your vocals are going in the red (even one syllable), why don't you just turn everything down. Miroslov mentioned that. Turn down your vocal so it doesn't peak, and then turn everything else down. If your master even comes CLOSE to peaking, your mixing way too hot. If it's just the vocal track that's peaking, then you're still mixing way too hot.

Turn it down.
 
Which compressor are you using? If it has the same kind of automatic gain compensation like the Logic one has, that's your answer right there.

And, BTW, based upon your description, anyway, I wouldn't attack it with compression. If it's just one syllable, I'd just knock down that syllable either with the volume automation or by manually knocking down the volume of just that one syllable with the editor.

G.
 
RAMI said:
I could have sworn about 5 people told you it's the auto-make up gain. It's AUTOMATIC. It doesn't matter where you have your Make-up gain slider set.
Click to expand...
I could have sworn I wasn't talking about makeup gain, but ratio. :eek:

@SouthSIDE Glen: fair enough, I just like to understand the tools I'm working with, so bear with me.

Strictly speaking it IS logical to try this with a compressor, no? I mean, in essence that's what a compressor is supposed to deal with, right? Oops volume goes over threshold, please lower volume. Increasing the ratio should emphasize said lowering of volume, so your hot signal cools down more as your ratio goes up.
So if the auto gain makes the compressor do the exact opposite, and I can't turn it off, then they should give it another frikken' name?

It's like an oven that makes everything cold. That's no oven; it's called a fridge.
 
singlespeak said:
I could have sworn I wasn't talking about makeup gain, but ratio. :eek:
Click to expand...

You're not understanding how they work. Yes, if you increase the ratio, the make-up gain will compensate and your volume will get louder and louder. That's just how they work, whether it makes sense to you or not.

And compressing, or even turning down a peak doesn't make sense to me, unless it's a really big spike. The only reason you're noticing this, most probably, little spike is because you're mixing too hot and that little spike happens to put you in the red. If you mixed at proper levels, you probably wouldn't even notice this little volume change.

I know you're going to ignore it again, but I'll still say it. There's no reason for anything to go in the red on a mix. You're mixing too hot.
 
Look, RAMI, I appreciate the time you're taking to respond. The dynamic range of my voice is wide in this particular recording and at one point I also came closer to the mic while I should have been moving away. So there's quite a leap there, nothing too dramatic, automation actually works quite well, I did that before trying the compressor. But I'm not asking about mixing too hot or not - which I might be, no doubt - I'm frustrated with my compressor regardless of the specific context. I'm re-recording the vocals anyway, that's not the point.

So ok, I'm not understanding how they work you say. Am I wrong in saying that auto gain is a parameter over which I have no control, can't turn off, and which actually undoes some of the normal functionality of a compressor without it? If not, then that's a bit much, innit?
 
singlespeak said:
I could have sworn I wasn't talking about makeup gain, but ratio. :eek:

@SouthSIDE Glen: fair enough, I just like to understand the tools I'm working with, so bear with me.

Strictly speaking it IS logical to try this with a compressor, no? I mean, in essence that's what a compressor is supposed to deal with, right? Oops volume goes over threshold, please lower volume. Increasing the ratio should emphasize said lowering of volume, so your hot signal cools down more as your ratio goes up.
So if the auto gain makes the compressor do the exact opposite, and I can't turn it off, then they should give it another frikken' name?

It's like an oven that makes everything cold. That's no oven; it's called a fridge.
Click to expand...
Can a compressor fix that problem? Yes, it can, and there's nothing intrinsically wrong with hitting it with compression, but it's kind of overkill to throw a plug at a single spot problem when all it really requires is some good ol' fader jockeying or a simple waveform edit. It's kind of like using the garden hose to put out a candle ;).

And the compressor *is* still compressing; the ratio still holds. But on every compressor, there's an output stage that comes after the compressor stage itself. Most compressors give you a manual control at that stage called "output gain" or "makeup gain", which allows the user to increase the over all volume of the compressed signal to "make up" for the loss in overall volume caused by the compression, if desired. Sometimes it's desired, sometimes it's not.

You see, many times folks want to compress the dynamic range - i.e. close the "height" of the signal from bottom to top - but don't want to lose the overall perceived volume or signal level. This is what the "makeup gain" is for, to make up the overall volume without losing the actual amount of compression.

Some compressor plugs treat the users as dummies, and try to automate that makeup gain. They automatically push up the volume by an amount proportional to the amount of gain reduction applied in the compression stage. Theoretically this would mean that - if it were a linear relation - when you set the gain reduction ratio to infinity-to-1, it would supply an infinite amount of makeup gain and send the signal level up through the roof,

I personally hate the idea of compressors with automatic makeup on the output, it just encourages poor practices on the part of the noob user and leads to compressor confusion like this thread right here. But unfortunately the promise of one button simplicity attracts a lot of newbs and sells product for the manufacturer.

G.
 
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