Automatic Extraction of Minimum-Phase Response

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Bohdan
Posts: 46
Joined: Mon Dec 07, 2020 8:31 am

Automatic Extraction of Minimum-Phase Response

Post by Bohdan »

Dear All,

Anybody who ever measured a loudspeaker driver using MLS or ESS measurement systems faced a problem with placement of FFT window. In order to obtain true minimum-phase phase response, the FFT window must be located where it should be.

I have produced two papers describing the method of dealing with this issue.
In the first paper, I introduce Inverse Hilbert-Bode Transform and it’s application.

https://www.bodziosoftware.com.au/IHBT_White_Paper.pdf

The second paper describes an automated method for extracting minimum-phase phase response and more.

https://www.bodziosoftware.com.au/Automated_IHBT.pdf

If you have any questions, please contact me on
bohdan@bodziosoftware.com.au


Best Regards,
Bohdan
meloV8
Posts: 37
Joined: Thu Dec 03, 2020 10:45 am
Location: Poland

Re: Automatic Extraction of Minimum-Phase Response

Post by meloV8 »

Hi Bohdan,
thanks for those papers, especially the second one with the new automatic option. As I understand it, this is some feature of the future version of SoundEasy?
Bohdan
Posts: 46
Joined: Mon Dec 07, 2020 8:31 am

Re: Automatic Extraction of Minimum-Phase Response

Post by Bohdan »

Dear All,

This paper concludes the 3-part miniseries on Minimum-Phase extraction.

https://www.bodziosoftware.com.au/Louds ... zation.pdf

Best Regards,
Bohdan
Bohdan
Posts: 46
Joined: Mon Dec 07, 2020 8:31 am

Re: Automatic Extraction of Minimum-Phase Response

Post by Bohdan »

Hi Lukasz,

Yes, the automated extraction is intended for V28.

Best Regards,
Bohdan
dcibel
Posts: 43
Joined: Sun Dec 13, 2020 6:39 am

Re: Automatic Extraction of Minimum-Phase Response

Post by dcibel »

If the intent is for manufacturers to agree on a standard method of data distribution, that is going to be a hard sell. I can in fact assure you that will never happen. The industry is driven by commercial interests, not by the DIYer that can't decide which driver to purchase until he's completely designed a crossover ahead of time.

Reading the 3rd part of this trilogy, after determining the exact perfect minimum phase of the driver, you still are requiring a reference delay offset to a single common plane, usually the baffle. That is determined by simply measuring from the mic to the baffle, which leaves me with the real question at hand - how much better will my speaker be by all this min phase determination, versus simply taking the as-measured phase, measuring from mic to baffle and then removing that delay from the measured phase. What is left, is the min phase + delay (excess phase) to the baffle surface, would you agree? Provided that my measurement is loud enough that the noise floor is well "out of band" and with frequency response bandwidth of 40kHz or more, how much error is there in this process that is being corrected for by the HBT and IHBT processes? I'm not trying to downplay any importance of min phase data, but that comparison would really help me understand the benefit.
Bohdan
Posts: 46
Joined: Mon Dec 07, 2020 8:31 am

Re: Automatic Extraction of Minimum-Phase Response

Post by Bohdan »

Hi,

I have no illusion, that manufacturers would implement the described algorithm. But at least, they are now exposed to the rest of the world,
knowing, that they could easily provide more technical information to the buyer. They can no longer hide behind "it's impossible to measure minimum-phase response".

The real winner could be the DIY community. Imagine one person in some part of the world would measure a driver and publish the file on any of the DIY forums for everybody else in the world to use. This could grow and multiply quickly. Up until now, any attempt to create such DIY database failed because there was no easy way to actually measure minimum-phase response. Now you can do it.

Determination of the Acoustic Centre Offset is a "side-effect" of the minimum-phase response measurement. My papers were designed to explain the new method and highlight it's benefits. They were explained in Part 3. As far as the ACO is concerned, it is helpful in design the delay equalization circuits for both: passive and DSP equalized loudspeakers. In addition, ACO is part of the acoustic ray geometry in modelling process.

If you use different method - run with it.

Best Regards,
Bohdan
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