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14th April 2010, 01:38 PM  #1061 
diyAudio Member
Join Date: Aug 2007

I ran a simulation in BEM (which solves the wave equation by numerical integration), I attach the results. They show the throat impedance and power response of the system. Two things are evident:
 Lec2 seems to be closest to the more accurate BEM simulation  Hornresp results are amazingly close to the BEM results. Unfortunately I can't simulate a 180 deg. LeCleac'h horn in an infinite baffle (2Pi), so I can't comment on how well Lec4 holds up against BEM. The problem with Lec3 vs. Lec4 may be the 2Pi termination, but maybe David has more thoughs on this. Bjørn 
14th April 2010, 01:42 PM  #1062 
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Join Date: Aug 2007

For your interest, here are the plots for throat impedance and SPL power response for Lec3. Again Hornresp is very close.
The dip in the response, visible in both the SPL power response plots, comes from rear and front chamber resonances. They also appear in Hornresp, if masking is turned off. That they are so similar, is because I use the same rear chamber model in the BEM program as Hornresp uses. Bjørn 
15th April 2010, 06:38 AM  #1063  
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Join Date: Jun 2007

Hi David_Web,
As Bjørn has so kindly shown, in this particular case the Lec2 predictions are the most accurate. This is because the Hornresp Le Cléac'h horn isophase wavefront model is optimised for horns having a mouth flare tangent angle of not less than 90 degrees. The isophase wavefront model is therefore not really suited to the two examples given. Both Lec1 and Lec2 are severely truncated Le Cléac'h horns  the mouth flare tangent angles are only 26 degrees. The two examples are effectively identical to catenoidal hyperbolicexponential horns having the same dimensions  this can readily checked by changing L12 from 'Lec' to 'Hyp'. The Hornresp plane wavefront model is optimised for use with slow flaring horns, which is why those results are the more accurate in this case. Quote:
If JeanMichel happens to read this, then he might care to comment  after all, he is the real expert on Le Cléac'h horns :). Thanks. Once again, JeanMichel would be the best person to comment on the level of "bass boost" that could be expected by extending the horn to a fullyformed 180 degree mouth. It seems from Bjørn's BEM simulations that the Hornresp Lec3 predictions are reasonable at least. Kind regards, David
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15th April 2010, 07:03 AM  #1064 
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Join Date: Nov 2006

@Bjørn
Thanx for the calculations. Which BEMSoftware did you use? 
15th April 2010, 07:14 AM  #1065 
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Join Date: Jun 2007

Hi Andrew,
Not really. Prior to Version 5.50 the wavefront model was chosen by the user, but now Hornresp makes this decision. In most cases the horn system you wish to simulate will fall clearly into one wavefront model category or the other, and either model will still allow you to optimise a particular design  unless you happen to be sitting right on the crossover point. It should be rare that a problem will actually arise in practice. In a worstcase scenario, the maximum difference between the two models is still only about 3dB anyway :). Kind regards, David
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15th April 2010, 07:27 AM  #1066  
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Join Date: Jun 2007

Quote:
Many thanks for these simulations, they are greatly appreciated! I am very pleasantly surprised at how well the Hornresp predictions hold up against your BEM results  almost too good to be true, considering the profound differences in the calculation methods used :). Kind regards, David
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15th April 2010, 12:18 PM  #1067 
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Join Date: Sep 2008

Thanks.
I did a multi segment conical approximation and got close to what you showed above. The "bass boost" seem to happen in any pi. BTW Thank you for the Horn wizard!!! I love it. Spent the last hour "butchering" the art of horns. I don't mean to pick on my wonderful new toy but, Could you change the sliders to behave like the TH version, so they don't "loop back" to 0 every thousand cm2. It's a little hard to keep track on size based on slider position. Could you also introduce this behavior on chambers as going from a very large to smaller would take a very long time unless you exited the wizard and typed it in. The BEM simulations really shows how good hornresp really is if you treat it well. Thanks. 
16th April 2010, 06:42 AM  #1068  
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Join Date: Jun 2007

Hi David_Web,
Quote:
If hyperbolicexponential flares are used for Lec1 and Lec2 (which would most likely be the case in practice) then the results predicted by Hornresp for the two horns are effectively identical. There is no longer a crossover point issue. Quote:
* The throat acoustical impedance of a Le Cléac'h horn having a mouth flare tangent angle of 120 degrees, as predicted and measured by Bjørn. * The throat acoustical impedance for the same horn, as predicted by Hornresp. A comparison of the results would seem to suggest that the Hornresp model is valid for Le Cléac'h horns having mouth angles up to 120 degrees, at least. Kind regards, David
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16th April 2010, 07:24 AM  #1069  
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Join Date: Jun 2007

Hi David_Web,
Quote:
Quote:
Quote:
The Loudspeaker Wizard description on page 11 of the Help file refers. Kind regards, David
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16th April 2010, 08:59 AM  #1070  
diyAudio Member
Join Date: Sep 2008

Quote:
The front chamber now takes one sweep per liter to get anywhere so some sort of value depending multiplier to make adjustment easier would be nice. *tries to remember to read the manual every release* 

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