FIR Filter Rewindowing | New in FIR Designer, FIR Designer M & FIR Creator EX

Rewindowing provides user-adjustable shortening of a FIR filter – from sources other than FIR Designer – so that it can be loaded into FIR-capable amplifiers & processors with specific tap length limits (and with a minimal change in filter response). Rewindowing is available within FIR Designer’s DTP (direct-to-processor) functions, which currently support Lake and Powersoft.

For example, a FIR filter with a tap length of 512 can be rewindowed to 384 so it can be loaded into a processor with a 384 tap-length limit.

Side-loaded FIR filters can be in almost any file format and are sample-rate converted to the output channel sample rate.

The rewindowed FIR filter can be sent – along with IIR, Gain, Polarity & Delay settings – via DTP to the target (Lake or Powersoft) device.

Rewindowing is only accessible to software licensees (since DTP isn’t visible in demo versions); this video shows how it works (using Lake as an example). Its based on FIR Designer but FIR Designer M & FIR Creator EX include identical functionality.

Existing FIR Designer 1 license-holders are eligible for a USD $100 coupon towards the first-year purchase of FIR Designer 2+ just contact us.

Short Learning Curve for FIR Designer M Users

Our most full-featured & complex product – FIR Designer M – is now also the easiest in our FIR Filter product range to learn to use, thanks to its integrated Help. Since the launch of FIR Designer in 2016, our focus has been on using all available development time on new features & functionality. Providing how-to-use documentation wasn’t a priority since most users were able to quickly master the software’s intuitive workflow, and could take all the time needed to experiment with a demo version prior to purchase. However, as we’ve released new, increasingly-complex features, there has been a marked rise in queries about usability, as well as multiple repeat visits by users to the instructional videos.

So, with the launch of FIR Designer M last November, we decided to divert some of our development time to creating an integrated web-based Help. Website statistics indicate high usage and it’s clear that the Help function is shortening the learning curve, as well as highlighting lesser known features and filter types. We’ve learned some lessons about the value of in-app documentation, and will look at expanding Help functionality in other products in the future.

Get a free demo of any Eclipse Audio software on our website.

FIR Designer M Help Page for the Channels tab

IIR Filters: Emulation Accuracy Across Brands

Some IIR filters may produce different results when used in various amplifier/processor brands. Common causes are differences in the way each brand’s software interprets some filter parameters, like Q and bandwidth (BW), and in the conversion between Q & BW. The differences typically appear in parametric (peaking) filters and shelf filters.

The plots below show various implementations of a 10 kHz 10 dB parametric filter. The upper row is for a sampling rate of 48 kHz and the lower for 96 kHz. There is no simple translation between the BW and Q in each implementation, so to help with the comparison, all have been manually & approximately matched by adjusting the BW or Q to give ~ +5dB at 5 kHz. Looking at the both the magnitude and phase, it’s clear that the implementations are different, particularly near the Nyquist frequency of 24kHz for the 48 kHz sampling rate. The 96 kHz implementations are more similar because Nyquist has been pushed out to 48 kHz. However even when overlaid there are subtle differences.

In the plots, the implementations in the right two columns (labelled Linea Research & Powersoft) each have unique equations to create 2nd order analog filters, which are then mapped to 2nd order digital designs using the Bilinear Transform with frequency warping. The plot on the left uses a method proposed by Sophocles Orfanidis which attempts to keep the digital filter shape close to the analog design near the Nyquist frequency. (This method is very similar to the implementation used by Lake Processing). For more details see the 1996 AES Paper “Digital Parametric Equalizer Design with Prescribed Nyquist-Frequency Gain.”

FIR Designer (& FIR Designer M) can be used to emulate IIR filters as part of a complete loudspeaker preset. They both incude multiple branded ‘IIR Filter Mode’ options (including Linea Research & Powersoft) that address these alternative IIR implementations. The Linea Research & Powersoft modes accurately emulate IIR filters for these brands (for loading into System Engineer, and Armonia, respectively). The Generic mode is the default option and offers IIR filters common to all three modes as well as Chebyshev & Elliptic high-pass and low-pass filters and Neville Thiele notched crossovers.

When using FIR Designer to emulate IIR filters for other brands, we recommend trying all 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. Note: the Lake FIR 3-way module can accept raw IIR filter coefficients generated by any of the three modes.

For all modes, IIR filter parameters and raw coefficients can be exported to text files, & the parameters copied to the desired control software. This process is automated for some brands (via Direct-To-Processor functionality).

[2022 Update: FIR Designer & FIR Designer M now include One-click IIR conversion between brands, in the IIR Reference Editor]

Differences in IIR implementation between Powersoft & Linea

Useful links

New Linea Research & Powersoft IIR Filter Modes in FIR Designer

Subscription licensees can access the latest download on the “update available” dialog within FIR Designer or FIR Designer M.

Now available in FIR Designer 2.9 & FIR Designer M 1.1: Eclipse Audio has recently collaborated with Linea Research to offer a “Linea Research” IIR filter mode which provides accurate emulation of Linear Research filters, including the unique Hardman crossovers filters, when creating mixed IIR+FIR loudspeaker presets. FIR filters can be exported as SFI files and loaded into System Engineer, for use in Linear Research processors and amplifiers.

Also available is a “Powersoft” IIR filter mode whose Q parameter (for all-pass and peaking filters) now exactly matches Powersoft Armonia. Using the Powersoft Direct-To-Processor functionality, mixed IIR+FIR processing chains can be exported to XML and loaded into Armonia for use in Powersoft amplifiers.

Both the Linea Research and Powersoft IIR filter modes enforce parameter limits – gain, frequency, bandwidth & Q – specific to each brand.

In FIR Designer and FIR Designer M, all IIR filters from previous versions are grouped under a “General” IIR filter mode and include bandpass, low and high shelf, low-pass and high-pass Bessel, Butterworth, Chebyshev I & II, Elliptic, Linkwitz/Riley & Neville Thiele notched crossovers.

For all filter modes, IIR filter parameters and raw coefficients can be exported to text files.

When switching between IIR filter modes, FIR Designer and FIR Designer M make a best-effort automatic conversion of all filters, although some manual adjustment of bandwidth or Q may be necessary. Where filter types are unavailable, a similar filter type is chosen.

FIR Designer & FIR Designer M can export FIR filters in a variety of formats for loading into most FIR-capable products, including Lab Gruppen (LAKE), QSC, MiniDSP, Electro-Voice, Symetrix, Dynacord, BSS, DFM, Biamp & Apex.

Download a free demo (Windows or Mac) of either FIR Designer or FIR Designer M.

Please note, the FIR Designer 2.9 feature updates apply to all existing subscription licenses and any new perpetual licenses purchased. Existing perpetual license-holders – 2.8 and below – will receive a bug-fix update only. For more details see the FIR Designer Release Notes.

FIR Designer Release Notes    FIR Designer M Release notes

Labelled screenshot of FIR Designer - New Linea + Powersoft IIR Modes

Screenshot of FIR Designer - New Powersoft & Linear IIR Filter Modes

New FIR Designer Pricing

To coincide with the launch of our new flagship product – FIR Designer M (a multi-channel version of FIR Designer) – the pricing options for the existing (single-channel) FIR Designer have been restructured.

A subscription license of FIR Designer now costs $299 (was $399) AND there is an alternative option to purchase a perpetual (non-updateable) license of FIR Designer for a $599 one-off cost.


subscription license of FIR Designer requires an annual recurring payment to stay active. The feature set will expand over time, as license holders receive ongoing free updates to the latest version, including all new features & improvements. Our development efforts will continue to be focused on regularly updating FIR Designer to expand & improve functionality for annual license holders. Tech support is available & feature requests welcome.

A perpetual license of FIR Designer is a one-time purchase. The software can be used indefinitely with no additional payments, however the feature set will be ‘frozen’ at the time of purchase, with no access to any updates or new features for license holders. To upgrade to a newer FIR Designer version in the future, a new license would need to be purchased. Tech support is provided for bug reports only (critical bug fixes supplied if required).

The SUBSCRIPTION and PERPETUAL versions of FIR Designer are identical at the time of purchase, but will differ over time.

Already Own a FIR Designer 2 License?

Existing FIR Designer 2 license-holders will have their annual license payment automatically dropped to $299 per year when it is next due; alternatively license-holders can continue to pay $399 per year at the next-scheduled due date, but immediately upgrade to a FIR Designer M license. (Contact us to make the change to FIR Designer M).

Already Own A FIR Designer 1 License?

FIR Designer 1 was discontinued November 2017. Existing license-holders are eligible for a USD $100 coupon which can be used once towards a purchase of FIR Creator, FIR Designer (subscription/annual OR one-time license) or FIR Designer M. Contact us (providing your license key) to request a $100 coupon.


Introducing FIR Designer M (Multi-way)

Build a complete loudspeaker preset for multiple channels simultaneously with FIR Designer M. It utilizes the same easy-to-follow workflow of FIR Designer but provides up to 6-way, simultaneous multi-channel filter design. Create finite impulse response (FIR) filters and complete mixed FIR + IIR filter loudspeaker presets for single and multi-way loudspeakers, using multi-way loudspeaker driver measurements. Simulate the combined multi-way frequency response and time/frequency (wavelet) behaviour.

FIR Designer M also includes a new integrated Help menu to further enhance the software’s usability.

Learn more about FIR Designer M or download a free demo (Windows or Mac).

To coincide with the launch of FIR Designer M, the pricing of (single channel) FIR Designer is changing. Learn more.


Existing FIR Designer 1 license-holders are eligible for a USD $100 coupon towards the first-year purchase of FIR Designer M. Existing FIR Designer 2 license-holders are eligible to convert their license to a FIRd M license at no additional cost (just contact us to set it up).

Loudspeaker Measurement Averaging in Averager vs. FIR Designer

Combining multiple measurements, especially for spatial averaging, can result in a more accurate filter design & overall system response. Eclipse Audio has three software products which can average an unlimited number* of loudspeaker measurements – of any supported format – into a single response: Averager, FIR Designer M and FIR Designer. All accept loudspeaker measurements from any tool, such as Systune, Easera, Smaart, Klippel & others.

Averager is a stand-alone software application enabling the creation of an averaged response for use in any other audio & plotting tools (ie. not just those developed by Eclipse Audio).

FIR Designer M & FIR Designer both include the same averaging functionality as an optional step within the filter design workflow. Generate a response for export or for use within the program (from the Import tab).

Averaging filenames and settings can be saved as an ‘Averaging Session File’ which can be can be shared between FIR Designer M, FIR Designer & Averager.

*Subject to computer memory limits
About Measurement File Sample Rates

Measurement files can have different samples rates and don’t have to match the FIR filter design sample rate when using FIR Designer M or FIR Designer. All measurements are resampled to the FIR filter design sample rate as they are loaded.

Tutorial: Loudspeaker Measurement Averaging in “Averager”:

Tutorial: Loudspeaker Measurement Averaging in FIR Designer*:

  • Select the ‘Measurement Averaging’ tab
  • Select a directory of measurements.
  • Choose a “Reference” measurement. All other measurements are automatically time aligned to this reference.
  • For each of the other “Comparison” measurements, adjust the time-delay, average weighting and polarity.
  • Select one of four averaging modes: Complex, Power (flat, zero phase), Power (minimum phase) and Power (minimum phase + excess reference phase).
  • Finally, in FIR Designer copy the average measurement to the Import tab for use in your FIR or IIR+FIR filter design, or export the average response to file. (Export is not shown in video below.)

*Same instructions apply for FIR Designer M

FIR Designer 2.7.0 Expands Averaging Functionality & Adds Kaiser-Bessel Windowing

Current licensees can access the latest download on the “update available” dialog within FIR Designer 2.

FIR Designer 2.7.0 is now available and includes both new features & updates:

  • The “Measurement Averaging” tab has been completely updated to the new workflow and plotting, recently released in the stand-alone Averager application. (Averaging session files can be exchanged between both FIR Designer 2 and Averager).
  • FIR filter windowing now has a Kaiser-Bessel option with adjustable alpha.
  • The parameter table drop-downs open in one click.
  • Parameters dialog has been updated for ease of use and flexibility for the future.

See the Release Notes (for all versions) here.

Learn more about FIR Designer or download a free demo (Windows or Mac).

Existing FIR Designer 1 license-holders are eligible for a USD $100 coupon towards the first-year purchase of FIR Designer 2; just contact us.

Screenshots from Averager, the measurement averaging tool from Eclipse Audio

Introducing Averager – New Loudspeaker Measurement Averaging Tool

By popular demand, we’ve developed a stand-alone application for averaging multiple loudspeaker measurements into one measurement, which can then be used in other audio tools, plotting tools & in FIR Designer’s ‘Import’ tab. Averager accepts loudspeaker measurements from any tool, such as SystuneEaseraSmaartKlippel & others. It expands on the functionality found within FIR Designer‘s ‘Measurement Averaging’ tab with improvements to the workflow, additional plot comparisons & statistics, & the ability to save the average response to file. Averager can load an unlimited number of measurements – subject to computer memory limits – and features a new, integrated help function. The updated Averager functionality will be included in FIR Designer’s ‘Measurement Averaging’ tab & available to FIR Designer license holders.

Learn more about Averager or download a free demo (Windows or Mac).

Existing FIR Designer 1 license-holders are eligible for a USD $100 coupon towards the first-year purchase of FIR Designer 2; just contact us.

FIR Designer 2.6 now imports Monkey Forest SPK & Klipppel Impulse Response text files

Current licensees can access the latest download on the “update available” dialog within FIR Designer 2.

FIR Designer 2.6.0 is now available and includes new import options plus some user interface updates. Notable updates (since the last update post for v2.4):

  • Monkey Forest (FourAudio) SPK files and Klippel Impulse Responses can now be loaded. Steps to extract data from a Klippel Impulse Response plot can be found here.
  • When importing a measurement file on the Import or Target tab, when “Normalise magnitude to max” is set, the “Magnitude offset (dB)” field now displays the normalisation gain. This is useful starting point when setting the offset gain manually.
  • Time based plots now have an optional millisecond (ms) scale and right-click now enables zoom-to-maximum (in addition to the “Max” buttons).
  • The Target file now has a use “Phase only” option which helps with matching loudspeakers based just on phase.
  • All lists and filter prototype tables now have a “Reset” option to take them back to defaults.

See the Release Notes (for all versions) here.

Learn more about FIR Designer or download a free demo (Windows or Mac).

Existing FIR Designer 1 license-holders are eligible for a USD $100 coupon towards the first-year purchase of FIR Designer 2.6; just contact us.

Klippel Impulse Response files and Four Audio's Monkey Forest SPK files supported in FIR Designer

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