Jean Michel on LeCleac'h horns - Page 114 - diyAudio
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Old 1st June 2011, 12:34 PM   #1131
Jmmlc is offline Jmmlc  France
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Hello Lars,

Quote:
Originally Posted by revintage View Post
Hey Jean-Michel,
The path difference seem to be somewhat critical.
The only way to lengthen the rear wave must be to make a larger baffle than necessary to mount the driver.
What is your opinion about negative sideeffects?
In a dipolar scheme, to obtain some gain at low frequency we try to have both the front and rear waves in phase at the listener position (this means a difference of path around the half of the wavelength. If we use the common OB approach in the bass register then we need a very large baffle.

In the field of my "Horn Open Baffle" concept I prefer to use the rise of the group delay of the horn near the frequency cut-off, than to lengthen the path of the rear wave. This is what makes the concept original.

Best regards from Paris, France

Jean-Michel Le Cléac'h
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Old 1st June 2011, 01:33 PM   #1132
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OK Jean-Michel,
It is actually the influence on the upper-register that makes me wonder. These are few sims and the model.
Attached Images
File Type: png 40.PNG (24.0 KB, 522 views)
File Type: png 50.PNG (23.8 KB, 514 views)
File Type: png 70.PNG (24.2 KB, 514 views)
Attached Files
File Type: txt 15a.txt (389 Bytes, 14 views)

Last edited by revintage; 1st June 2011 at 01:46 PM.
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Old 1st June 2011, 02:39 PM   #1133
Jmmlc is offline Jmmlc  France
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Hello Lars,

Quote:
Originally Posted by revintage View Post
OK Jean-Michel,
It is actually the influence on the upper-register that makes me wonder. These are few sims and the model.
No harmful differences to my eyes.

It is always a bit difficult to acertain which difference of pathlength is the most realistic to be introduced in an Hornresp model.

Better to use what seems logical and the more logical accords to the drawing I gave.

http://www.diyaudio.com/forums/attac...athlengths.gif

Then, as always, there could be some discrepancy between the simulation and the measurement and, as ever, you'll need to perform some optimization...

Best regards from Paris, France

Jean-Michel Le Cléac'h
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Old 1st June 2011, 03:30 PM   #1134
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Hello again Jean-Michel,

The simmed -3dB of 400Hz or 800Hz is a big difference. If the 800Hz is OK, then the wavelength giving 400Hz -3dB must be considered as harmful. But will this happen IRL?

I am a little confused as I didn´t think the rear wavelength should affect the higher frequencies this much. The low end doesn´t seem to be affected much.
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Old 1st June 2011, 03:53 PM   #1135
Jmmlc is offline Jmmlc  France
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Hello Lars,

You are right, what I expalined is related to the low frequency. IN the medium frequency (over 150Hz or 200Hz) due to the increased directivity of the rear wave, there will be no interference between the rera and front waves.
But as it is strongly related to the geometry of the system, this is the kind of problem that Hornrresp cannot solve (for the moment).

Above 200Hz better to consider that the front wave only arrives to the listener and so better to not use the "combined" module.

(Note: for a horn bass-reflex VOT "style" having a vent on the front of the box the recommandation will not apply.)

Best regards from Paris, France

Jean-Michel Le Cléac'h

P.S. : I leave Paris for a geological trip and I'll be back only on Tuesday June 14th.
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Old 1st June 2011, 03:55 PM   #1136
Jmmlc is offline Jmmlc  France
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Quote:
Originally Posted by Jmmlc View Post
Hello Lars,

You are right, what I explained is only related to the low frequency part of the response. Due to the increased directivity of the rear wave at medium frequency (over 200Hz), there will be no interference between the rear and the front waves.

But as it is strongly related to the geometry of the system, this is the kind of problem that Hornrresp cannot solve (for the moment).

Above 200Hz better to consider that the front wave only arrives to the listener and so better to avoid the use of the "combined response" module.

(Note: for a horn bass-reflex VOT "style" having a vent on the front of the box the avove recommandation doesn't apply.)

Best regards from Paris, France

Jean-Michel Le Cléac'h

P.S. : I leave Paris for a geological trip and I'll be back only on Tuesday June 14th.
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Old 2nd June 2011, 05:57 AM   #1137
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Default Path Length Difference in Hornresp

Quote:
Originally Posted by Jmmlc View Post
Imagine the path of the front wave at LF, it is a straight line between the loudspeaker and the listener position.
Hi Jean-Michel,

Just to clarify - the way that Hornresp defines path length difference, d1 in your path length drawing (attachment 1) should show the distance from the horn mouth to the nominal listening position, not from the horn driver diaphragm to the listener - see attachment 2 for further details.

To illustrate the difference using your definition of d1 as the basis for the comparision:

For d1 = 150 cm and d2 = 200 cm your drawing would suggest that the path length difference value required for Hornresp is d2 - d1 = 50 cm.

Assuming that the horn axial length (L12) = 50 cm, then the path length difference value actually required for Hornresp is d2 - (d1- L12) = 100 cm.

Hope this makes sense :-).

Kind regards,

David
Attached Images
File Type: gif pathlengths.gif (4.5 KB, 481 views)
File Type: png Pathdiff.png (9.8 KB, 476 views)
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Old 2nd June 2011, 11:20 AM   #1138
Mark Kravchenko --- www.kravchenko-audio.com
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I always was under the assumption that the path length difference could be used for things like an open baffle or H or U frame type baffle to calculated the roll of due to the path length. Now it seems there is a further use. Thank you David!

And Jean-Michel has been a constant source of great tips as well. Thanks to both of you.
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Old 26th June 2011, 05:52 AM   #1139
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Default Le Cléac'h Horn - New Profile

Hi Everyone,

I recently had a close look at the Le Cléac'h horn flare - I was particularly interested in checking the accuracy of the constructed profile against the actual hyperbolic-exponential expansion rate upon which it is based.

For the purposes of my investigations I considered a Le Cléac'h horn having the following parameters:

Throat diameter = 2.54 cm
Cutoff frequency = 320 hertz
T = 0.8

I first compared Jean-Michel’s original and improved (2007) profiles against the actual hyperbolic-exponential expansion rate, with the wavefront area equivalent radius being plotted against axial length. See Lec_Original.png and Lec_Improved.png attached.

I then realised that it should be possible to construct an even more accurate Le Cléac'h profile. See the results in Lec_New.png attached. The Hyp and Lec curve values are identical to 11 decimal places.

The three horn profiles are shown together in Lec_Compare.png attached. It is interesting that the new profile makes the Le Cléac'h horn even slightly more compact.

Hornresp currently simulates Le Cléac'h horns using Jean-Michel’s "improved profile". Because the difference in performance between the improved profile and new profile is likely to be insignificant, the Hornresp model will not be changed. An option will however be added in the next release to allow raw data for the new profile to be exported, so that constructors can build the perfect axisymmetric Le Cléac'h horn, if so desired.

Jean-Michel has been given details of the method used to construct the new profile.

Kind regards,

David
Attached Images
File Type: png Lec_Original.png (38.4 KB, 131 views)
File Type: png Lec_Improved.png (38.3 KB, 121 views)
File Type: png Lec_New.png (38.0 KB, 112 views)
File Type: png Lec_Compare.png (38.6 KB, 156 views)
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Old 27th June 2011, 11:29 AM   #1140
doug20 is offline doug20  United States
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I own IWATA horns now.

How do people mount them?? Is it just some simple wood braces for the horn to sit on?

Also what is the impact of molding a fibreglass shell around the back of the horn and making a box so I can mold it into a bass bin to make one speaker?
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