The Postfilter module allows you to shape the tone of
the distorted signal. When adding distortion to audio, harmonics and additional
frequencies are often created. Sometimes these are desirable, but other times
you might want more control over the rolloff of the highs and lows. The Postfilter
module allows you to rolloff these frequencies.
Even though the Postfilter module operates like the Prefilter module in terms of selecting and adjusting filters, there are differences between the two modules:
1) In general, the Postfilter module is used for rolling off the highs and lows, so only two filters are provided. The Prefilter module has three to provide additional midrange control and sweeping effects.
2) The Prefilter module provides envelope and LFO triggering of filters, while the Postfilter module provides static filters only.
3) The Postfilter module can operate in a multiband mode. This concept of a "multiband filter" is explained below:
Multiband Postfiltering:
When using multiband distortion, the audio is split up into independent bands for processing. Each band can receive its own type and amount of distortion, generating harmonics that can be outside of the original band. For example, you might apply distortion to a single band between 100 and 200 Hz, but the distortion created can create harmonic frequencies all the way up to 20 kHz.
In order to independently filter multiband distortion before it is combined together into a single band, the Postfilter module can operate as a multiband postfilter.
To activate multiband postfiltering, click the Multiband button in the upper right corner.
When using the Postfilter as a multiband module, the spectrum is updated to only display the frequencies within that band. This allows you to see the harmonics and frequencies created by any individual distortion applied to that band, and filter them independently of the other bands.
Tips
1) In many cases, box modeling can provide natural sounding "postfiltering" of distortion without the need to apply additional postfiltering within this module.
2) Unless you are working with multiband distortion, there isn't any need or benefit to using the Postfilter in multiband mode.
Note: This help file is a quick reference for basic Trash functions and controls. We have separate "how to" guides that provide tips and techniques for getting the most out of Trash. You can download these guides from http://www.izotope.com/products/audio/trash/guides.html