The final dynamic processor that we're going to examine this week is the
limiter. Now a limiter is an extreme downward
compressor. So it's a downward compressor with a
ratio set very high, above 10 to 1. A ratio we tend to consider.
Is a limiter. But the role of the limiter has been kind
of changing in contemporary music. The original role of a limiter was just,
was to stop peaks. Was to make it so the signal never goes
above a certain level. And in that, it was very, it was very
useful. You think of a live stage situation
Think if you have a, vocalist. Right.
And they tend to just drop the mic or swing it around or scream into it, and,
you don't want to hurt your audience. So you put a limiter on that microphone
so that if they do drop it, if they do scream into it, the level never gets
above that specific set point. That threshold.
And you set that so that the, the loud sound doesn't hurt your speakers.
And doesn't hurt your audience. So it had a kind of protective role.
And in that, you want to make sure the sound never gets above a specific level,
so it would be a compressor with a very fast attack, and even a little look
ahead, and also a very high ratio. So you would think of it as, you might
even hear the term a brick wall limiter, meaning it's never going to get above a
specific level. Now in that instance, those limiters tend
not to sound very good. They have more of a protective role.
And at that they're very good at but they don't really sound great as you get to
them. As we've kind of moved on through
technology and get more digital signal processing, the role of a limiter has
kind of evolved to be a loudness maximizer.
And some plug-ins are actually calling it then, calling it that now.
And so an original limiter. As a protective device would just come on
once in a while, right? hopefully not even at all, but when it
did, it would just turn on and turn off very quickly, trying to be transparent,
and just protecting the audience. And the contemporary limiters, which are
also known as loudness maximizers, they're kind of running more often, and
their goal is to make things sound as loud as possible.
But not increase the amplitude, right? Remember that distinction between
loudness and amplitude? Amplitude is measurable but loudness is
the perception. So the idea with this contemporary
loudness maximizers is to make it seem louder but not actually increase the
volume at all. So we're going to examine the kind of
traditional role of a limiter and kind of also look at how a loudness maximizer
functions in a contemporary mix. We mentioned earlier that a limiter is an
extreme compressor: it's a compressor with a very, very high ratio.
And, to function as a brick wall limiter, it also has to have a very fast attack,
or a low attack time. That way, it will capture and stop all
the transience, so nothing is allowed to get above that threshold.
I have this compressor set up to be in one of these very fast attack and release
limiting modes. And the reason I'm bringing this up now,
is I want to point out the issues involved in heavy limiting.
heavy limiting in compression is a, is a common thing in contemporary mixes.
You want to make things sound as loud and powerful as possible.
But In doing so, you do introduce the chance of distortion.
And we have to be aware that we always have this dynamic range.
This issue between noise and distortion. We saw earlier that using compressors
heavily and using the make up gain increases the noise.
And now we'll see that pushing compressors and limiters too hard
introduces distortion. And it's always your job to stay between
those two things. Or when you go beyond them to do it
musically. So we'll start this example like we did
the gate and compressor with the more abstract example.
And I have a low sign wave tone that I'll play through this plug in.
[SOUND] So we see with the sign wave that we have energy at a single frequency.
[SOUND] [SOUND] And it's quite loud as it is.
Now I'm going to start compressing this signal with a very fast attack and
release compressor. Basically I'm in limiting mode now
[SOUND]. And I'll reduce my threshold.
Watch what happens. [NOISE] We see that limiting this with a
very, very fast attack and release has distorted the wave shape, and has given
us a series of upper harmonics. We've, we have distorted the signal, and
this looks very much like the clipping distortion we analyzed earlier this week.
So we have to be very careful with limiters and compressors and even gates
not to get in the situation where we're adding up our harmonics that we don't
want. Now this can be used musically but
usually you set up a compressor to avoid this kind of situation.
This is most commonly a problem with low frequency notes, like I have in this
example here. Because the attack and release time on my
compressor are set so fast, that the compressor is responding to every single
oscillation of that low wave form causing this distortion.
So if we want to remove this we have to start manipulating our attack and release
times but there's always trade offs. Let's try it out.
This time I'll start raising my release time.
And we see that's. Changing the distortion, because that
compressor's not allowed to move as fast, we're reducing the amount of distortion.
I'll raise up my attack time a bit. A little more release, and now we're to
the point where I don't really have audible distortion -- I don't see the
distortion here and I also don't hear it in my headphones.
So now I'd be free to lower this threshold even further.
I'm reducing the sound without introducing unwanted distortion.
The trade-off is this. If I play a key now, if I play this note,
we're going to see a little bit of that transience let through.
Let me make it more obvious by increasing attack even more.
So we see a little bit of that transient at the beginning of the note.
The limiter's not moving fast enough to avoid that initial click.
So that's the trade off we're always working with, with limiters.
We want very fast attack times, and fast release times if possible, but when we do
so, we introduce the chance of distortion.
If we increase the attack time, we introduce the chance that something is
going to get through the compressor or limiter.
Let's look at how a limiter functions now.
And we'll see, it's going to be very similar to this, but I want to show you
one difference. In a limiter, we have a threshold control
that is directly associated with a makeup gain.
So as I lower threshold, it automatically brings up the output gain.
And we're going to hear, this is going to be very similar to what we did with the
compressor. Let's try it out.