L2—UltraMaximizer Software audio processor User's Guide
Waves L2 software guide page 1 of 18
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 environment, whether for high-resolution 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 file 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 prevent 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.
Waves L2 software guide page 2 of 18
Chapter 2 - Some secrets of digital 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 of the L2 breaks down 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.
ABOUT MAXIMUM LEVEL
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 confidence in situations where brickwall limiting is important.
ABOUT MAXIMUM RESOLUTION
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).
Waves L2 software guide page 3 of 18
WHY USE THEM, AND WHAT ARE THEY?
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).
A BIT ABOUT IDR™
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 are available. The L2 features 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 software L2 plug-in from Waves, both featuring 9th-order noise shaping (the original L1 software has 2nd-order noiseshaping).
Waves L2 software guide page 4 of 18
Chapter 3 - Using the L2
THE PEAK LIMITER SECTION
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.
Waves L2 software guide page 5 of 18
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.
THE IDR SECTION
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.
Waves L2 software guide page 6 of 18
Loading...