FIR Designer

May 19, 2014
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Michael,

Thanks. Yep I understand how coherence works in Smaart; I just wanted to make sure my understanding of how that data is used by FIR Designer.

There are a number of features I'd love to see in the software, and I'm not going to bomb in with all of them immediately, until I have a better grasp of the tool. However I would find a cursor readout for X & Y values, when over any graph quite useful. I know this may be a little more complex than I'd like to imagine on account of some tabs, displaying five or so graphs on the same pane.

Best,

Phillip
 

Michael John

Junior
Jun 25, 2011
351
9
18
Sydney, Australia
eclipseaudio.com
Thanks for the suggestions, here and via email. I'll look in them. Just a few thoughts in response to your email.... for everyone here.

Your suggestion of a strength or % parameter on the Auto Mag and Auto Phase bands is a great idea and fairly easy to code.

Also, I've been thinking about how to give differing priorities to boosts and cuts in the Auto Mag process. The challenge is defining what is a boost and what is a cut, but I have some ideas that might work.

Auditioning functionality is something I started on about a year ago but it's not yet complete. Basically WAV file playback with the FIR filter switchable on/off and in the "off" case, ensuring time alignment with the peak of the "on" case.

Kind regards,
Michael
 

Michael John

Junior
Jun 25, 2011
351
9
18
Sydney, Australia
eclipseaudio.com
In response to Phillip's suggestions, the latest version 1.24.1 includes measurement smoothing on the Import tab, and the option to do either Complex or Power smoothing on the magnitude - similar to SMAART.

Also new are five linear-phase brick-wall crossover filter prototypes; denoted by their length in milliseconds. The longer the length, the sharper the filter. (The filter delay is half the filter length and the stop band is below -100 dB.)

Kind regards,
Michael
 
May 19, 2014
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Thanks for being so responsive Michael.

I think it would be useful in the audition functionality to switch between a handful of prototype FIR candidates.

I am curious to hear from Michael, or anyone else, what the use cases for the maximum phase filters in the Mag Adjust pane are. I can see the the phase response is opposite of a minimum phase filter with the same parameters (and thus a 1khz 1oct +6dB min phase boost + a 1kHz 1oct +6dB max phase boost, will result in a +12dB linear phase boost), however I am not certain in what particular situations this would be preferable to a minimum or linear phase filter (apart from experimenting and seeing if it tends closer to a flat phase response). Experiences or suggestions?
 

Michael John

Junior
Jun 25, 2011
351
9
18
Sydney, Australia
eclipseaudio.com
Hi Phillip,

The maximum phase option, on the Mag Adjust tab, mainly came about because it was very easy to implement. (The IR is just the time reverse of the minimum phase IR.) And, as you alluded to, applying maximum phase EQ on a minimum phase response will tend the response towards flat phase and take some of the load off the Phase Adjust tab; if flat phase is the intended result.

Kind regards,
Michael
 
May 19, 2014
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Thanks Michael.

I've got some FIR's loaded into London Architect now. I notice LA truncates the value of each coefficient to 7 digits (6 decimals), I'm not sure if this is a UI convince, but ought one be concerned about error being introduced via this truncation? I haven't yet had a chance to load this onto a Blu and Smaart the result to see how well it conforms to the trace in FIR designer.

It also managed to add a coefficient, so my 400 FIR became 401. Odd.

Phillip
 

Michael John

Junior
Jun 25, 2011
351
9
18
Sydney, Australia
eclipseaudio.com
Hi Phillip,

Yep, I noticed the London Architect UI truncating also. I've not looked into this closely but in BSS filtered speaker measurements, I've not seen any oddities which have made me go back and check. I also didn't notice any coefficient count oddities but that's not to say they didn't happen. (FWIW a value of 1e-6 is about -120 dB FS.)

Kind regards,
Michael