Arboretum Ionizer

EQ and dynamics-processing plugin

by Michael Cooper

Ionizer-MAS front panel

A gush of new plug-ins has recently flooded the market in support of Mark of the Unicorn's MAS platform and its two DAW programs, Digital Performer and AudioDesk. Among the me-too equalizers, compressors and delay-based effects, Arboretum's Ionizer stands out. Its unique approach brings a big bag of new tricks to the table.

Ionizer provides equalization, upward and downward compression/limiting, upward and downward expansion, and a frequency morphing function to MAS users. But Ionizer is no garden-variety EQ and dynamics processor. Picture a 512-band splitband compressor. Or frequency-conscious noise reduction controllable across hundreds of separate bands. Ionizer allows you to tweak audio in ways that are impossible with any other MAS plug-in. And it sounds great.

Minimum requirements
Ionizer requires a 120 MHz PowerMac, although a 200 MHz or faster processor is recommended. (601 and 604 chips will do.) Mac OS 7.6 and higher are supported. You'll need 16 MB free RAM. PC users are out of luck, but Mac versions are also available for AudioSuite, Premiere and Arboretum's stand-alone HyperEngine.

I tested Ionizer primarily in AudioDesk using Mac OS 7.6.1. My Power Computing PowerCenter 132 (Power Mac clone) is hot-rodded with a 300MHz Newer Technology G3 upgrade card, 96 MB of RAM, an Orange Micro SCSI Grappler UltraWide host adapter and a 9GB UltraWide Seagate Barracuda hard drive. Ionizer was always very responsive and never crashed once during a couple of months of use.

Ionizer supports mono and stereo files in the Sound Designer II and AIFF formats. Twenty-four-bit files are supported, and the internal processing is 32-bit floating point. Processing occurs in real time.

HyperEngine Transport palette

How does it work?
Ionizer splits the audio spectrum into 512 independent frequency bands, each with its own gain boost/cut. A Spectrum function analyzes the audio you select and maps its frequency response on an X-Y plot. Frequencies are plotted along the horizontal axis, amplitude along the vertical axis on the left side of the screen. Ionizer then automatically generates red and blue curves that help determine the threshold and ratio of processing. These curves initially parallel the audio's frequency profile for convenience's sake, following the ups and downs in response, but they can be exhaustively edited.

The red curve denotes the threshold for processing. When audio levels surpass the threshold and cross into the transition zone between the red and blue curves, processing is increasingly applied. (The closer the blue curve is to the red curve, the higher the processing ratio becomes.) Beyond the blue curve, full processing takes place. You click and drag handles (called “fit points”) along the red and blue curves to tweak their shape and set the threshold and ratio of processing independently across individual frequency bands.

To determine how much gain boost or reduction will take place in any given frequency band, a black gain curve—also automatically generated—is manipulated on the same plot. This curve can be thought of as a frequency-sensitive range control. Its gain is determined by a vertical amplitude scale along the right side of the screen. The gain settings of the black curve also help determine, along with the blue curve, the ratio of processing.

Sounds complicated? It is, at least initially. The comprehensive manual is a must-read, and you should plan to spend at least a day getting to know the interface and various functions. Professionals with a background in dynamics processing will be up and running fairly quickly.

In control
Although there is only one set of controls for both channels of a stereo track, Ionizer processes the left and right sides independently and dynamically. The type of processing you get is determined by the placement of the red curve in relation to (above or below) the blue curve, and whether the black curve is effecting gain boost or cut.

The display can get a little crowded, but you can hide individual curves to see and edit the others more clearly. A zoom function is included, but it can't zoom in/out independently along vertical and horizontal axes, a minor limitation. You can break each curve up into hundreds of bands by creating multiple “fit points,” handles that sit on a center frequency to form a knee. Even if less than 512 fit points are drawn (you'll need less than 20 for most work), Ionizer always processes 512 independent bands per channel. You can drag fit points around with a hand tool or nudge them with your keyboard's arrow keys.


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Reprinted with permission from Mix Magazine's May 2000 issue.
Copyright © 2000 by Intertec Publishing.