Waves Audio L2 Ultramaximizer User Guide

L2—UltraMaximizer

Software audio processor

User's Guide

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Chapter 1 - About the L2

The L2-Ultramaximizer is the third-generation software processor, combining
an advanced peak limiter, level maximizer and a high performance re­quantizer and dithering system called IDR (Increased Digital Resolution). In
addition, the L2 software processor includes Waves' ARC Auto-Release
Control system, and ninth-order noise-shaping in the IDR implementation.
Processing in the L2 is 48-bit (double precision) processing, offering
improvements for all resolutions, and the opportunity to dither to a 24-bit
output for archives and DVD. The L2 offers superb requantization for all bit­depths, including 24, 22, 20, 18, and 16-bit outputs. The development of L2’s
lookahead peak limiter provides the mastering engineer with the capability to
increase sound file resolution and production master levels with precise
control and dithering options.

Waves IDR™ process brings more choices, greater control, and unmatched
compatibility to the mastering environ ment, whether for high-resolutio n CD or
low-resolution multimedia. IDR offers two dither types and three noise­shaping curves for optimal processing in a wide variety of applications and
with a wide choice of source material.

While the operation of conventional limiters is well understood, the limiter
section of the L2-Ultramaximizer is capable of a very fast, overshoot-free
response, and once the limiter threshold has been set, the user can then go
on to define the actual peak level that the processed signal will reach. Once
set, limiting and level re-scaling becomes a one-shot process.
For mastering purposes, the peak level of the processed signal would
normally be set to 0dB, or just below 0dB. Because a typical digital audio file
of music contains many high intensity, short duration peaks, simple
normalization of the f ile may still result in a low average signal level. Using the
L2-Ultramaximizer however, it is generally possible to significantly increase
the average signal level of a typical audio file without introducing any audible
side effects. In the event that a deliberately limited sound is required however,
there is more than adequate range of the limiter parameters to recreate
‘vintage’ effects such as level pumping or severely limited dynamic range.
The Ultramaximizer is specifically designed for mastering, digital editing,
multimedia, and any application that requires limiting and/or requantization of
the digital signal with highest quality. In order to ensure the maximum possible
resolution of a processed signal, it is very highly recommended that the L2 be
used last in the processing chain. Failure to observe this will not preven t L2
from working, but you should be aware that both the absolute brickwall limiting
AND the benefits of IDR requantization will be compromised and will need re­limiting to maintain the original level.

The L2 is available as a stereo processor only. It will not show under mono
inserts and to process mono data you will have to make it stereo or bus it to a
stereo Auxiliary input.

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Chapter 2 - Some secrets of di gital audio

In order to make the best use of the L2-Ultramaximizer, it is important that we
explain some of the less obvious implications of digital audio. Once these
have been explained, you will understand why Waves thought a product
such as L2 was necessary and you will be a in a better position to make use
of its powerful features. The operation o f the L2 breaks dow n into two main
areas:

1 - maximum level of the digital signal through proprietary peak control.
2 - maximum resolution of the signal through dithering and noise-shaping.

BOUT MAXIMUM LEVEL

A

The maximum level of a digital signal is governed by the highest peak in the
file. Simple normalization finds the highest peak, then raises the entire signal
so that this peak is at the maximum value. However, many of these peaks
may be of very short duration and can usually be reduced in level by several
dBs with minimal audible side effects. Those familiar with digital editing
systems may even have proved this for themselves by ‘redrawing’ some
trouble-some peaks by hand. By transparently controlling these peaks, the
entire level of the file can be raised several more dB than by simple
normalization resulting in a higher average signal level.
The L2-Ultramaximizer avoids the possibility of overshoot by utilizing a
lookahead technique that allows the system to anticipate and reshape signal
peaks in a way that produces the bare minimum of audible artifacts. Because
there is no possibility of overshoot, L2 can be used with absolute conf idence
in situations where brickwall limiting is important.

BOUT MAXIMUM RESOLUTION

A

Any digital signal processing that alters the original digital data (mixing, gain
changes, EQ, dynamic processing, etc.) generally increases the number of
bits required to represent the signal. Conventional truncation results in a loss
of signal-resolution each time the signal is processed. The human ear uses
this low level information to construct a mental image of the stereo
soundstage, so any compromise in this area manifests itself as a loss of
spaciousness and transparency. Waves’ IDR prevents this loss of critical low­level detail. Even when processing 16-bit signals, it is normal to process with
at least 24 bits resolution, or more (as in the L2, which is now double­precision). However, as soon as the resolution is pulled back down to 16 bits
by rounding or truncation (by removing the bottom 8 bits), the resulting
rounding error produces an audible distortion at low signal levels, and a
permanent loss of digital resolution that can never be recovered. If the audio
signal is repeatedly processed and truncated back to 16 bits, the losses
accumulate, causing a significant loss of fidelity, most evident as a loss of the
tonal subtleties of low-level sounds within a mix. The human ear uses such
low level information to construct a mental image of the stereo soundstage, so
any compromise in this area manifests itself as a loss of spaciousness and
transparency.
The solution is to properly dither and noise-shape a signal each time the
wordlength is increased then reduced (such as nearly every digital signal
process will require).

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HY USE THEM, AND WHAT ARE THEY

W

Proper dithering is simply this: before the requantization (reduction of the
wordlength), a precisely controlled amount of noise (termed ‘dither’) is added
to the signal. This can convert the low-level nonlinear distortion caused
by truncation into a simple steady hiss, thereby removing all traces of low­level non-linearity, but at the expense of a very slightly increased background
noise. Obviously, increased noise levels are not ideal in high quality audio
applications, but fortunately, the perceived level of this dither noise can be
greatly reduced by ‘shaping’ the noise in such a way that it falls into an

area of the audio spectrum where the human ear is least sensitive.

The main point of maximum resolution is simple: to ‘capture’ the best possible
quality into a shorter wordlength (smaller bit-depth) from a longer wordlength
(higher resolution).

BIT ABOUT

A

IDR is a Waves proprietary noise shaping dither system developed by the late

Michael Gerzon and Waves, and signifies a major advance in preserving and
actually increasing the perceived resolution of the digital signal being
processed. You can utilize IDR each time during subsequent processes (for
16-bit storage), or once at the end of a high-resolution chain (say, 24-bit), in
order to ensure that the final signal has the maximum resolution possible.
IDR is of particular benefit when data is deliberately requantized from 48-bit to
24-bit, 24-bit to 20-bit and so on.
Dithered outputs of 24, 22, 20, 18, and 16-bit ar e avai l abl e. The L2 featur es
double-precision resolution, that is, for TDM systems, all internal limiting and
gains calculated with 48-bit fixed precision. Dithering back to 24-bit output
is now possible for the new DVD and other delivery media, as well as for
archives of masters.
By using the IDR implemented within the L2-Ultramaximizer, optimum results
may be achieved during final file preparation, mastering, and quantization or
requantization. The greatest possible implementation of IDR available is in the
L2-hardware limiter and this s o ftw ar e L2 plug -i n from Waves, both featuring
9th-order noise shaping (the original L1 software has 2nd-order noise­shaping).

IDR™

?

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Chapter 3 - Using the L2

HE PEAK LIMITER SECTION

T

1 - Open a soundfile in your host application. Select part or all of the soundfile
you wish to process with the L2. Pass audio through the L2; for more
information, see your host application system manual.
2 - Listen to the output of the L2. Set the threshold of the limiter by dragging
the left triangle (Threshold) down. Leave the Out Ceiling setting at the
maximum value: 0.0 dB.
3 - When the threshold is exceeded by the signal, you will see the Gain
Reduction indicated on the single Attenuation meter to the right. Set the
threshold about 4 to 6 dB lower than the peaks in the Threshold meters
(input). You will see that you have from 4 to 6 dB of peak limiting indicated on
the Attenuation meter (output).
4 - You’ll notice that as you pull the Threshold down, the output level goes up.
Leave the Out Ceiling setting at the maximum value:

0.0 dB. This is your maximum peak output.
Notice that you have significantly increased the output level. If your threshold
is at -12dB, then you have pushed the signal up 12 dB (not that this is
recommended)! With moderate gain reduction, the maximum level of a file
can be significantly increased with minimal audible effect.
Only the signal above the threshold is limited; all signal below the threshold
has a constant gain change that is controlled by the difference between the
Threshold and the Out Ceiling. It is this function of the L2 that allows you to
maximize the level with the amount of headroom desired.

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5 - Leave the ARC™ (Auto-Release Control) engaged at all times unless you
have a very specific type of limiter behavior, such as pumping or distortion
effects. ARC calculates the release time every sample for optimum level
with minimum artifacts. For nearly every possible source, ARC will outperform
a fixed release time.

HE

T

After reading this overview, make sure to read the chapter - Important IDR
info - which will offer you complete IDR technical information so that you may

be able to better choose from the IDR options in L2. Take the time to read
about this new technology so that you may achieve the best processing for
your application.

In the L2, there are two types of Increased Digital Resolution dither
technology: type1 and type2. The differences between them will likely
influence your choice for your project.

• type1 gives no nonlinear distortion.

• type2 exhibits lower dither level.
It is up to you to choose no distortion or lower dither level for your soundfile.
More information is in the section called IDR Dither Type & Noise-shaping

combinations.

IDR

SECTION

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