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Old 8th July 2013, 01:55 PM   #3601
tb46 is offline tb46  United States
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Hi David,

Rane has some nice papers on filters, one is on the Bessel filter: A Bessel Filter Crossover, and Its Relation to Others .

Regards,
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Old 8th July 2013, 03:00 PM   #3602
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Jeff B View Post
..........The first order filter is only Butterworth. You can't vary the Q on the first order filter.

I do not know the coefficients for higher order Bessel, or even if they exist.
the coef for all the traditional filter types exist.

As far as I'm concerned the standard single pole RC or CR filter is a Butterworth with a Q=Sqrt(2).

Some have said I am wrong, but I just left them believing I'm the fool.
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Old 9th July 2013, 07:32 AM   #3603
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Hi Jean-Michel, Jeff, Oliver and Andrew,

Thanks for your comments - they help me to better understand how the Hornresp Filter Wizard could perhaps be enhanced a little.

Kind regards,

David
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Old 9th July 2013, 02:13 PM   #3604
tb46 is offline tb46  United States
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Hi David,

I hope I didn't open too much of a can of worms for you, but I now understand a little more about using Hornresp and Jeff's software.

One question that comes up when using the Filter Wizard is: is it possible to add a button to the Filter Wizard that transports the filtered SPL curve into the main window, so that the filtered SPL curve can be used as the basis for impulse and group delay graphs? I'll attach a typical Filter Wizard window as an example.

Either way, thank you so much for your continued effort, and for making Hornresp such a wonderful tool.

Regards,
Attached Images
File Type: jpg TH_SPL_both.jpg (30.3 KB, 172 views)
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Old 10th July 2013, 08:04 AM   #3605
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Quote:
Originally Posted by Jeff B View Post
Phi = -ATAN2 (X,Y)
Hi Jeff,

Just to clarify - am I correct in assuming that you actually meant to say Phi = ATAN2 (-X,Y)?

Kind regards,

David
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Old 10th July 2013, 08:30 AM   #3606
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Hi Oliver,

Quote:
Originally Posted by tb46 View Post
is it possible to add a button to the Filter Wizard that transports the filtered SPL curve into the main window, so that the filtered SPL curve can be used as the basis for impulse and group delay graphs?
Unfortunately from an operational perspective that would complicate things greatly for me. As far as the Filter Wizard itself is concerned though, I hope in the next release to include three additional active filter charts showing filter phase shift, filter group delay and overall filter plus speaker group delay - all results calculated in real time.

Kind regards,

David
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Last edited by David McBean; 10th July 2013 at 08:36 AM.
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Old 10th July 2013, 10:13 AM   #3607
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Quote:
Originally Posted by David McBean View Post
Hi Jeff,

Just to clarify - am I correct in assuming that you actually meant to say Phi = ATAN2 (-X,Y)?

Kind regards,

David
No, the way I wrote it is the way it is used in Excel. However, there are several things in Excel that are quirky, like needing to convert to Radians. I'm not sure if the way you wrote it would yield the correct result, but it would be easy enough to test and see.
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Old 11th July 2013, 07:27 AM   #3608
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Quote:
Originally Posted by Jeff B View Post
I'm not sure if the way you wrote it would yield the correct result, but it would be easy enough to test and see.
Hi Jeff,

For a 4th-order Butterworth low-pass filter with a cutoff frequency of 100 Hz:

Phi = ATAN2 (-X,Y) gives the result shown in Attachment 1.
Phi = -ATAN2 (X,Y) gives the result shown in Attachment 2.

Phi = ATAN2 (-X,Y) removes the phase wrapping at 100 Hz, but shows the phase starting at 180 deg rather than at 0 deg. I have noticed that this "unwrapped" presentation often seems to be the format of choice, which is why I sought the clarification. It makes no difference to the group delay results of course, which way the phase is calculated.

Kind regards,

David
Attached Images
File Type: png Attach1.png (50.4 KB, 143 views)
File Type: png Attach2.png (50.9 KB, 144 views)
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Last edited by David McBean; 11th July 2013 at 07:32 AM.
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Old 11th July 2013, 09:50 AM   #3609
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Quote:
Originally Posted by David McBean View Post
Hi Jeff,

For a 4th-order Butterworth low-pass filter with a cutoff frequency of 100 Hz:

Phi = ATAN2 (-X,Y) gives the result shown in Attachment 1.
Phi = -ATAN2 (X,Y) gives the result shown in Attachment 2.

Phi = ATAN2 (-X,Y) removes the phase wrapping at 100 Hz, but shows the phase starting at 180 deg rather than at 0 deg. I have noticed that this "unwrapped" presentation often seems to be the format of choice, which is why I sought the clarification. It makes no difference to the group delay results of course, which way the phase is calculated.

Kind regards,

David
I am not sure what you mean by format of choice, but attachment 2 (-ATAN2 (X,Y) is the correct phase. For a 4th order slope the phase should be at 180 degrees at Fc and wrap at that point. Attachment 1 is not correct.
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Old 11th July 2013, 01:59 PM   #3610
tb46 is offline tb46  United States
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Hi David,

Post #3606: "...I hope in the next release to include three additional active filter charts showing filter phase shift, filter group delay and overall filter plus speaker group delay - all results calculated in real time."

Looking very much forward to that. Thanks,

Regards,
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