IIR Conversion: The IIR Reference Editor

in FIR Designer M & FIR Designer

One-Click Conversion

The IIR Reference Editor faciliates the swift creation of presets or tunings for identical IIR performance across different brands.

Easily & precisely convert IIR settings from one brand to another, in a single click.

(Where two products don’t have equivalent filter types, additional filters can be added & adjustments performed manually to ensure an exact match.)

IIR conversion solves the problem of standard IIR DSP settings often producing inconsistent results on various amplifier/processor brands. (For example, a parametric filter on a Linea Research processor doesn’t match a parametric filter on a Powersoft amplifier when using the same parameters.)

Common causes for these inconsistencies are differences in the way each brand’s software interprets some filter parameters, like Q and bandwidth (BW), and in brand differences in the conversion between Q & BW. The differences typically appear in parametric, shelf and all-pass filters, but can also be between Bessel filters where brands have different interpretations of rolloff frequency. Different products also have different IIR filter parameter limits. (Learn more.)

The IIR conversion functionality within the Reference Editor is able to automatically adjust the BW or Q (and sometimes other parameters) to achieve an exact match between brands, making it faster & easier to translate an IIR or mixed IIR+FIR preset from one brand of processor to another & ensure consistency. All filters are included, and where brands don’t have an exact matching filter type, a nearest match is chosen.

User-selectable IIR filter modes in FIR Designer M

Brands that have an IIR emulation mode in FIR Designer include Lake, Linea Research, Powersoft, QSC Q-SYS, Symetrix, BSS, Biamp Tesira, Marani, RAM Audio & RMS Acoustics. (A full-featured ‘Generic’ mode is also provided.)

Set any one of these modes as an IIR ‘reference’, and use one-click conversion to make a IIR filter set in another brand with a response that matches the reference, in magnitude and phase. The displayed response updates immediately.

It’s also possible to manually adjust any brand’s IIR filters to match another’s responses, & make adjustments to the filter set already created via one-click conversion.

No IIR Mode for the Brand You Need?

When working with processors without a branded IIR mode, the ‘Generic’ mode is the best place to start. It includes parametric, bandpass, notch, low and high shelf, low-pass and high-pass Bessel, Butterworth, Chebyshev I & II, Elliptic, Linkwitz/Riley filters, as well as Neville Thiele notched crossovers. (The ‘Generic’ mode uses Robert Bristow-Johnson Q & BW definitions for many filters.)

We recommend trying all available modes within the FIR Designer IIR tab, & comparing the plots displayed with the IIR plots generated by your own control software to determine which mode produces the closest match. (You may find one of the other branded modes provides a closer match than the Generic mode.)

Manually adjust the filters in the IIR tab until the response mimics your desired response. Then you can optionally set it as the ‘Reference’, so it’s filter set can be converted to other brands with the IIR Reference Editor.

IIR Export

IIR filter parameters and raw coefficients created within the IIR tab & IIR Reference Editor can be exported to text files (via the FIR Designer ‘Export’ tab), & the parameters copied to the desired control software. This process is automated (via Direct-To-Processor functionality) for Powersoft, Marani & Lake Processing. (Note: the Lake FIR 3-way & XP modules and the Lab Gruppen IPX series amplifiers, can accept raw IIR filter coefficients generated by any of the IIR modes.)

The IIR Reference Editor is available in FIR Designer M & FIR Designer and is only accessible to software licensees. (It’s not available in free demo versions of the software.)

We continue to expand the list of emulated brands.