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Old 22nd June 2009, 12:04 PM   #641
Eva is offline Eva  Spain
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Hi David

This new version of Hornresp with phase unwrapping is great, it offers a lot of functionality, but I still miss the ability to make it unwrap the phase with a delay value chosen by the user rather than the value that the program choses, which I often dislike Substracting the value entered from the group delay plot would be quite useful too.

Updating phase and group delay plots when the directivity option is used would be quite useful too, as I stated previously.

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Old 22nd June 2009, 01:00 PM   #642
thend is offline thend  France
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Hello,

I have try to simulate a standing wave in a tube (that's why I sent an e-mail to know the celerity of sound), but it's difficult to tune perfectly.

Anyway, it's almost possible: I have a quasi standing wave.

So, if i see a standing wave, i do not see the wave front, then it's not a wave front simulator but an acoustic amplitude simulator which does not the difference between wave front and reflected wave front!?

(my tube: 80 for diameter, 68,5 or 68,4 length for 400hz...)
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Old 22nd June 2009, 01:49 PM   #643
Eva is offline Eva  Spain
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BTW2: The plots that I got with this new version have already helped me to find better crossover settings for my horn system.
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Old 22nd June 2009, 02:35 PM   #644
Jmmlc is offline Jmmlc  France
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Hello David,

A less bothering question than my last ones (I hope...): what do you think if the logarithm of the displacment of the diaphragm logarithm was drawn? At HF I guess it will me more easy to study the displacment graph.

I know I can do it through export but if we have it inside Hornresp it will so convenient using the "compare previous" function to itself... to compare ausai-instantaneously different horns on the same driver.

Best regards from Paris, France

Jean-Michel Le Cléac'h
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Old 23rd June 2009, 07:14 AM   #645
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Default Re: Re: Re: Re: Re: Re: HORNRESP VERSION 22.10

Quote:
Originally posted by Jmmlc
As I don't have any measurement of the power response of the TAD TD2001 on a Le Cléac'h horn, what interest me is to compare my frequency reponse curves measured by me at various angle from the axis, with the simulated response (HR directivity tool).
Hi Jean-Michel,

Although the Hornresp directivity tools simulate the general characteristic behaviours of the different horn flare profiles reasonably well, the results are not necessarily 100 percent accurate in an absolute sense. Full FEM or BEM modelling will give more precise results, but at the expense of calculation times, as Bjørn Kolbrek has shown. Hornresp directivity results should be considered as indicative only.

Taking into account the above limitations in the Hornresp directivity model, is there still any value in adding the diaphragm constant acceleration option to the program?

Kind regards,

David
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Old 23rd June 2009, 07:22 AM   #646
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Quote:
Originally posted by Eva
I still miss the ability to make it unwrap the phase with a delay value chosen by the user rather than the value that the program choses, which I often dislike. Substracting the value entered from the group delay plot would be quite useful too.

Updating phase and group delay plots when the directivity option is used would be quite useful too, as I stated previously.
Hi Eva,

Sorry, but I have no plans at this stage to do any more work on the phase or group delay charts :-).

Kind regards,

David
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Old 23rd June 2009, 07:38 AM   #647
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Quote:
Originally posted by thend
So, if i see a standing wave, i do not see the wave front, then it's not a wave front simulator but an acoustic amplitude simulator which does not the difference between wave front and reflected wave front!?
Hi thend,

If I understand correctly, I think you might be trying to use the Wavefront Simulator for something more than it was designed for :-). It simply shows how theoretical isophase wavefronts propagate down a horn towards an open mouth - that is all. In real life, things are more complicated than that.

Kind regards,

David
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Old 23rd June 2009, 07:43 AM   #648
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Quote:
Originally posted by Jmmlc
What do you think if the logarithm of the displacment of the diaphragm logarithm was drawn?
Hi Jean-Michel,

Sorry, you will have to keep exporting your results :-).

Kind regards,

David
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Old 23rd June 2009, 08:51 AM   #649
thend is offline thend  France
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Quote:
Originally posted by David McBean

If I understand correctly, I think you might be trying to use the Wavefront Simulator for something more than it was designed for :-). It simply shows how theoretical isophase wavefronts propagate down a horn towards an open mouth - that is all. In real life, things are more complicated than that.

Hello,

If i tried to simulate something the software wasn't designed for, I will not have the desired result but I have the desired result ie a standing wave, which is not a propagate wavefront.

Or it's my reading of simulation that is not good.
With this simulation, I defined a standing wave with a center Stationary black area (0, node) surrounded by an alternating red (+, antinode) and green (-, antinode) area through the black (0).

I mean an alternating red>black>green>black>red>black>green...(+>0>->0>+>0>-...) with a (almost, depending of precision adjustment I think) stationnary position.
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Old 23rd June 2009, 11:49 AM   #650
Jmmlc is offline Jmmlc  France
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Default Re: Re: Re: Re: Re: Re: Re: HORNRESP VERSION 22.10

Hello David,

The question I raised, is quite independant on the ability of Hornresp to predict any frequency response at a given angle from the axis.

If, for a constant velocity source at throat, we compare BEM and Hornresp responses for different angles from axis, we can see that within an interval of frequency of 2 octaves above the frequency cut-off (illustrated case is for a Le Cleac'h horn having a cut-off of 425Hz, BEM simulations performed by Bjørn Kolbrek)Hornresp gives quite similar results until 40 degrees off axis.

The BEM simulations with a real compression driver show only a small difference with the constant velocity hypothesis.

When using the constant velocity hypothesis we allways obtain a rising on axial response of many horns (not only for the Le Cléac'h horn)

On the other hand we have dozens of axial response with the different drivers on Le Cléac'h horn or Kugelwellen horns or Tractrix horns... and they never show rising slope on-axis frequency response.

We have to explain why.

May be it is a question of distribution of pressure on the driver throat...

May be we have to question the constant velocity model used in the simulations...

Best regards from Paris, France

Jean-Michel Le Cléac'h



Quote:
Originally posted by David McBean


Hi Jean-Michel,

Although the Hornresp directivity tools simulate the general characteristic behaviours of the different horn flare profiles reasonably well, the results are not necessarily 100 percent accurate in an absolute sense. Full FEM or BEM modelling will give more precise results, but at the expense of calculation times, as Bjørn Kolbrek has shown. Hornresp directivity results should be considered as indicative only.

Taking into account the above limitations in the Hornresp directivity model, is there still any value in adding the diaphragm constant acceleration option to the program?

Kind regards,

David
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