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Old 28th June 2009, 09:05 AM   #661
thend is offline thend  France
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Quote:
Originally posted by David McBean


It doesn't really matter - isophase wavefronts can be considered to be defined by either the red, green or black lines.

Hopefully the attached example will make things a bit clearer.

Hello,

I think we do not understand at all each other.

Never mind.
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Old 28th June 2009, 01:30 PM   #662
GM is offline GM  United States
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Quote:
Originally posted by David McBean

As you say, just another one of life's little mysteries...
Greets!

You're welcome!

Mystery indeed! I rebooted, DL/installed V22.2, did a few sims and barely two days later awoke this morning to the low Vb message. DLing a couple of pdfs from a thread here are the only other 'updates' I'm aware of.

GM
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Old 29th June 2009, 05:27 AM   #663
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Quote:
Originally posted by thend
I think we do not understand at all each other.
Hi thend,

I suspect that you probably understand me okay, it's just that I am currently having some difficulty understanding you :-).

If anyone can clarify for me the concern that 'thend' has with the operation of the Hornresp Wavefront Simulator, then I would greatly appreciate it.

Kind regards,

David
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Old 29th June 2009, 05:50 AM   #664
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Quote:
Originally posted by GM
I rebooted, DL/installed V22.2, did a few sims and barely two days later awoke this morning to the low Vb message.
Hi GM,

Just a thought - do you leave Hornresp running all the time, or do you normally close it at the end of each session? If the program is left running permanently, then perhaps you could try shutting it down after using it, to see if that makes any difference to the virtual memory problem.

Kind regards,

David
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Old 29th June 2009, 01:57 PM   #665
Jmmlc is offline Jmmlc  France
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Hello David,


For what I understood Thend while using the Hornresp Wavefront Simulator tool on a tube having a given length obtained, at a given frequency, a quasi static pattern of pressure. Probably this happened at some antiresonance frequency for which the reflected wave by the mouth arrives to the throat in phase opposition with the wave emitted by the diaphragm. (it could also happen at a resonance frequency with a different pattern).
(I tried to replicate the situation but I could only obtain a slow down in the displacement of the black fronteer, without freezing).

I guess that Thend question is semantic for the most and is related to what definition we give to the word "wavefront". Even in his message Thend use the expression "propagate wavefront". (In the example of the tube at a resonance frequency there is probably a "direct wave propagation wavefront" and a "reflected wave propagation wavefront" at the same moment...).

For my own I use Mario Rossi's definition: "a wavefront is the surface linking at a given moment the points having the same given value for the considered parameter" (phase , pressure,... )

ref: Mario Rossi: "Electroacoustique".

http://www.amazon.fr/Electroacoustiq.../dp/2880740614


Best regards from Paris, France

Jean-Michel Le Cléac'h




Quote:
Originally posted by David McBean


Hi thend,

I suspect that you probably understand me okay, it's just that I am currently having some difficulty understanding you :-).

If anyone can clarify for me the concern that 'thend' has with the operation of the Hornresp Wavefront Simulator, then I would greatly appreciate it.

Kind regards,

David
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Old 29th June 2009, 02:11 PM   #666
Jmmlc is offline Jmmlc  France
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Default Re: Re: Re: Re: Re: Re: Re: Re: Re: HORNRESP VERSION 22.10

Hello David,

When it comes to acoustic impedance prediction we know that Hornresp gives accurate results.

ref: http://www.diyaudio.com/forums/showt...36#post1524736

post #76 ,#77 ,#78 ,#79


Do we possess equivalent prooves that the power response simulation is exact (is there any measurement to compare with....)

Could you summarize the reason why a constant velocity diaphragm model is often used for FEM, BEM horn simulations?

Best regards from Paris, France


Jean-Michel Le Cléac'h


Quote:
Originally posted by David McBean


Hi Jean-Michel,

The constant velocity diaphragm model is very straightforward, I wouldn't have thought that there could be too many problems with it.

Assuming the power response simulation is reasonably accurate, couldn't the rising on-axis pressure response prediction be due simply to Hornresp over-estimating "beaming" effects at higher frequencies - ie the actual beamwidth is not as narrow as that predicted by the program?

Would you still like a constant acceleration option to be added to Hornresp?

Kind regards,

David
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Old 29th June 2009, 04:11 PM   #667
GM is offline GM  United States
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Quote:
Originally posted by David McBean

Just a thought - do you leave Hornresp running all the time, or do you normally close it at the end of each session?
Greets!

When I'm not using it it, I normally keep it minimized in the task bar. I tried closing it each time when the problem began, like I've had to do with BoxPlot 3.07 ever since I was ~forced to 'upgrade' to XP Pro, but it didn't seem to make any difference, so went back leaving it open in the task bar.

GM
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Old 30th June 2009, 07:53 AM   #668
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Quote:
Originally posted by Jmmlc
For what I understood Thend while using the Hornresp Wavefront Simulator tool on a tube having a given length obtained, at a given frequency, a quasi static pattern of pressure.
Hi Jean-Michel,

Thanks for your thoughts. As far as the Hornresp Wavefront Simulator is concerned, the isophase wavefronts shown are simply the "contour lines" connecting points of equal phase across the 2-D horn schematic diagram - much the same as the notional curved surface areas used as the basis for constructing a Le Cléac'h horn profile.

The distance between the mid-points of two adjacent red or green "lines" is equal to one wavelength at the specified frequency. The attached example shows a tube with a length of 344 cm. The tube contains exactly 5 wavelengths at the sample frequency of 500 hertz, as one would expect.

Perhaps I should point out that the Wavefront Simulator shows relative phase, not relative pressure amplitude.

Not sure what else I can say :-).

Kind regards,

David
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File Type: jpg isophase.jpg (30.0 KB, 217 views)
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Old 30th June 2009, 08:05 AM   #669
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Default Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: HORNRESP VERSION 22.10

Hi Jean-Michel,


Quote:
Originally posted by Jmmlc
Do we possess equivalent prooves that the power response simulation is exact (is there any measurement to compare with....)
In theory, if the predicted throat acoustical impedance is accurate, then the power response should be okay also - assuming that the diaphragm acts as a rigid plane piston and that the driver parameter values are correct.

I am not aware of any specific comparisons between predicted and measured power response. Most tests done consider the pressure response only. For bass horns though, at low frequencies where directivity is not an issue, presumably the power response could be accurately determined in an anechoic environment. Certainly a number of Hornresp users have reported a close correlation between predicted and measured results for their bass horns, even when tested under less than ideal conditions, and with folds in the horns.

Provided that a compression driver can be suitably specified using the seven electro-mechanical parameters available in Hornresp, then the power response of a midrange horn with a compression driver should also be reasonably accurate.


Quote:
Originally posted by Jmmlc
Could you summarize the reason why a constant velocity diaphragm model is often used for FEM, BEM horn simulations?
I have no idea why this is done. Perhaps it is simply to 'normalise' results by excluding the effect of the driver, so that only the performance of the horn is considered.

BTW, since you haven’t confirmed that the diaphragm constant acceleration option is required, it will not be included in Hornresp :-).

Kind regards,

David
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Old 30th June 2009, 08:10 AM   #670
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Quote:
Originally posted by GM
but it didn't seem to make any difference, so went back leaving it open in the task bar.
Hi GM,

So much for that bright idea... :-).

Kind regards,

David
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