[EA Support]

EA Support

18 June 2020 at 11:35 am #180

Hi Sunil,

Even though your measurement system might be doing specific time windowing, the IR still has both loudspeaker phase and high delay which manifests as high phase slope when exporting as freq/mag/phase TXT. (I’m guessing this high delay is the time-of-flight across your chamber, plus soundcard buffer delays.)

In FIR Designer there is no error to give. The TXT file HAS phase and so the loading process is doing the best it can to interpolate the TXT file to the finer resolution FFT spacing. The high phase slope is the problem, and in this case is causing spurious distortion in the calculated IR. (You can see this on the FIR Designer Import tab if you expand the time axis and zoom the vertical axis.) If you truely want to ignore phase, then you can set all the phase values to 0 deg in the TXT file. (FWIW SMAART spectrum measurements come across to FIR Designer with 0 deg phase.)

In this situation it’s always best to avoid using log-frequency-spaced freq/mag/phase data – no matter how fine in resolution – for transfer between programs. Conversion to this format looses information which then causes problems when trying to reconstructed the impulse response – which is what FIR Designer is doing. It’s always best to transfer using an impulse response or time format, where information doesn’t get lost. (E.g. AFMG ETM files, or the time impulse as TXT or WAV.

>> And since Auto Mag should be trying to work on matching measured magnitude to target only, I do not see the relation to phase.

Auto Mag works with complex input and calculates the magnitude using either power averaging or complex averaging across frequency. You’re correct that power averaging should avoid issues of high phase slope but the additional distorting (added by the import interpolation process due to the high phase) is also causing problems in the Auto Mag.

I guess we could add an option to completely ignore phase on import, but it’s not something people normally want. When doing any filtering on a loudspeaker, most folks want to see both the phase of the filtering and the effect – both magnitude and phase – of the filter on the loudspeaker measurement.

Best,
EA Support

[EA Support]

EA Support

18 June 2020 at 10:27 am #177

And thanks for the suggestions. We’ll add them to the TODO list.

Best,
EA Support

[EA Support]

EA Support

18 June 2020 at 10:27 am #176

Hi Sunil,

I’ve looked over the project and measurement files. The measurement is a 3 column freq/mag/phase TXT file with very high phase slope. In other words the impulse response of this measurement wasn’t near time=0 in the measurement system, before the TXT file was exported. (In the excerpt below, the phase starts at -76 degrees and ends up < -40,000 degrees.) The file import process in FIR Designer does it’s best to interpolate this TXT file up to the internal FFT size, but very high phase slope causes errors in this interpolation. And both the interpolation errors and high phase slope are causing the Auto Mag problems that you are seeing.

Two suggestions. Either remove any bulk time offset from the measurement before exporting the freq/mag/phase TXT file, or export the impulse response itself as a time signal – TXT or WAV. With time signals, FIR Designer can remove bulk delay without any response error.

Note that freq/mag/phase files are great for plotting, but inherently loose information*, when compared to the time waveform IR.

* unless they are a linear frequency spaced FFT data.

Frequency Magnitude Phase
20 74.9498 -76.0055
20.3 75.0916 -78.8764
20.6 75.2281 -81.1653
20.9 75.2503 -82.5894
21.2 75.3959 -82.2123
…
18500 88.7457 -40505.1289
18750 88.765 -41041.2812
19000 88.7698 -41577.7695
19250 88.7277 -42114.3984
19500 88.6458 -42650.1914
19750 88.6929 -43186.1406
20000 88.7875 -43758.5703

Best,
EA Support

• This reply was modified 5 years, 10 months ago by EA Support.

[EA Support]

EA Support

12 June 2020 at 10:29 pm #173

BTW the same tutorial and others are on

FIR Filter Design Tutorials

Best,
EA Support

[EA Support]

EA Support

12 June 2020 at 10:27 pm #171

Thanks for sharing. Yes, we provided that to miniDSP sometime back. 🙂

Best,
EA Support

[EA Support]

EA Support

5 June 2020 at 6:03 pm #169

All our products can export FIR’s as TXT files that load into Powersoft Armonia. FIR Creator EX, FIR Designer and FIR Designer M also have a Powersoft DTP dialog where you can export an XML file, for Armonia, that includes gain, delay, polarity, IIR and FIR coefficients.

Best,
EA Support

[EA Support]

EA Support

5 June 2020 at 8:56 am #167

Hi Haff,

FIR Designer is available as a subscription license (with continual feature updates) and a perpetual license (with only bug fixes).

With the subscription license, a credit card is kept on file and charged annually. Shortly before the annual charge, you will receive an email notice and can cancel the subscription. Once the subscription is cancelled, the software reverts to demo mode and you can’t save projects, systems and can’t export filters.

With the perpetual license, you can use the product indefinitely.

All our products contact our license server periodically to verify that the license is still valid. This helps us reset your license in the event of a computer failure or loss.

Best,
EA Support

[EA Support]

EA Support

3 June 2020 at 7:35 am #165

Hi DKP,

Your FIR filter length of 400 at 48 kHz is way too short for the amount of LF magnitude and phase filtering you are trying to achieve. Filtering at lower frequencies requires longer filters, as does aggressive filtering – high Q and high slope regions in the magnitude and phase of the filter. Generally speaking a 400 tap filter (at 48 kHz) will struggle below approximately 500 Hz, and that can be seen in the “FIR Filter Frequency Response” plot on the Export tab. Powersoft amps can take at least 2048 length filters now and the modules might be similar. I’d recommend switching to just IIR filters at the point at which the FIR can’t go any lower.

Maybe take a look at the Audio FIR Filtering paper

FIR Filter Guide

It has examples of differing filter lengths.

One other suggestion. On the Import tab, using “Normalise magnitude to max” will result in much of the filtering being boosts. Maybe turn this off and use the manual “Magnitude off (dB)” field to place the smoothed response roughly either side of 0 dB. In this way the filtering will be a mix of boosts and cuts. Although I’ve not seen it yet, it’s possible some processors will run into headroom problems in the FIR filtering. And gain can always be made up later in a separate gain stage in the processor.

Best,
EA Support

[EA Support]

EA Support

29 May 2020 at 6:57 pm #162

Hi,

What file format are you using? With some formats such as WAV and single column TXT, the import process looks for the peak then loads from 1500 samples before the peak. Details are on https://eclipseaudio.com/loudspeaker-measurements/

If you know where the peak is, you can indicate it with a number at the end of the filename e.g. “measurement 423.wav”. Or to align time=0 with the start of the file, set the number at the end of the filename to 0. For example “measurement 0.wav”.

Best,
EA Support

[EA Support]

EA Support

26 May 2020 at 7:41 am #159

Thanks very much!

[EA Support]

EA Support

25 May 2020 at 12:53 pm #157

Hi daemlacken,

We mostly answer direct product questions but here are few things to try.

Regarding the measurements at different distances. You could design the filtering with the measurements you have then verify/adjust the relative driver levels later with measurements at a common distance outside (where there are no walls). Or take some new, gated measurements outside. I’d also suggest talking some off-axis measurements to help choose a crossover point where the drivers beam-width’s are roughly similar. Floyd Toole has published on the topic of subjective preference for loudspeakers with well-controlled directivity that varies smoothly over frequency.

Best,
EA Support

[EA Support]

EA Support

16 May 2020 at 7:50 pm #151

Hi Thomas,

The error calculation range to the left of the error plot can be adjusted by setting the start and the end frequencies to something within range. In your example the start frequency could be moved to maybe 400 Hz.

Generally deviations between the ideal and truncated FIR filter lower than -40 dB relative to the passband of the filtered response could be ignored (depending on the application). You could lower the “Y axis : min” value of the “FIR Filtered Frequency Response” – the middle plot – to see how the filtered response actually looks below 500 Hz.

Another thing you could try here is “DC Compensation.” When enabled, and when a HP filter is in use in the “Mag Adjust” tab, it ensures there is no DC offset in the FIR filter coefficients. This can improve LF rejection in the FIR filter in this situation.

Best,
EA Support

[EA Support]

EA Support

14 May 2020 at 7:16 am #144

In the FIR Designer “Export to Lake FIR 3-way module” dialog, there is a checkbox “FIR Filters Enabled.” Toggle this to enable/disable the FIR filters. All other processing, such as delay and IIR filters, still runs and is not affected by this setting.

Note: The “Gain” setting on the FIR Creator EX (and FIR Designer) “Gain/Polarity/Delay” tab is combined with the FIR, and so with the FIR filters disabled, the “Gain” setting is not applied.

BR
EA Support

[EA Support]

EA Support

14 May 2020 at 7:10 am #143

Hi vilcans,

Thanks for the suggestions. We’ve added these to the work list for consideration. All these are possible but some aspects may take significant work.

(All plots are current to 1/96th octave and exporting just the 1/96th data would be the easiest to implement.)

Kind regards,
EA Support

[EA Support]

EA Support

10 May 2020 at 10:06 pm #139

Hi,

>> Windows is running Lake LM44 v6.8.5 (install FIRd 2 plugin and Active)

The readme.txt (in the FIR Designer Lake Controller Plugin ZIP file) gives installation instructions.
Did you press CNTRL-L in the Lake Controller and did you see a message confirming that the plugin loaded?

>> They are in same network and connect LM44 Processor but i can’t connect LM44 in FIR Creator EX in DTP.

Make sure any firewalls are turned off on both computers.

>> Can you tell us some workflow about using LAKE and FIR Creator EX software and hardware setup?

In the Lake Controller, load the LAKE FIR 3-way module. (The file EmptyFir3Way_unlocked_with_user_range_v2.csm is provided inside the FIR Designer Lake Controller Plugin ZIP file.)

Then on

FIR Filter Design Tutorials

take a look at these videos
“FIR DESIGNER 2.3 | Direct-To-Processor Function (LAKE example) | Short Tutorial”
“FIR DESIGNER 2.3 | Direct-To-Processor Function (LAKE example) | Extended Tutorial”

Best,
EA Support