Jean Michel on LeCleac'h horns

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#1,322
Compromise

green heron said:
Does anyone have any thoughts on shortening a Le Cleac'h horn to reduce mouth size? This may come across as a ridiculous question as I understand the benefit of the Le Cleac'h horn is the rolled back mouth flare that reduces waves reflecting back into the horn, but the size of a 100 Hz Le Cleac'h horn (almost 2 meters across) gets impossible to integrate with a multi-way horn setup while keeping everything in phase and avoiding a DSP to compensate. I graphed several curves (Tractrix, Le Cleac'h with T=.55, Hypex with T=.55, and a 105 Hz Le Cleac'h with shortened mouth, the circumference of which is equal to one 105 Hz wavelength. The shortened Le Cleac'h comes in somewhere between a Tractrix and Hypex. It looks like the new profile would have the throat impedance of the Hypex (T=.5). Would the shortened Le Cleac'h horn retain response down to flare frequency better than the Tractrix while reducing reflections closer to the mouth better than the Hypex?
Thoughts?
Click to expand...

All alternatives to the full JMLC 100 Hz Horn will exhibit increased mouth reflectance and response ripple. The compromise I recommend is to use the JMLC 100 Hz profile and remove the mouth lips that curl back beyond a flare angle of 90 degrees. Replace them with those of a smaller constant radius. This should yield only a nominal increase in mouth reflectance.
Regards,
WHG
 
#1,326
sootshe said:
Can anyone tell me if I can cross an Azura AH 425 at 400Hz successfully. Mid driver will be the Great Plains Audio 390 (300Hz - 7K), crossed at 400 Hz (6db / octave).
Thanks,
John
Click to expand...

You'll need a larger horn to cross that low. You're trying to cross below the flare rate and with a 6 db slope, you'll only be down 6d at 200 Hz and down 12 db at 100 Hz. You'll need to either increase the crossover point significantly with your 6 db crossover or a increase the crossover point and increase the slope.
 
#1,327
Have both the JMLC-350 and the JMLC-200 here and have done extensive testing with both GPA 399 and 288 Classic Alnico. And a few other drivers as well.

Concerning bottom end the 200 horn works quite well all the way down to 350 Hz (I have used an Accuphase electronic filter with cards for 350, 500 and 650 Hz xover, with settings being either 12 or 18 dB/oct.)

JMLC-350 is quite ok down to 500 Hz, especially with the 18 dB/oct. setting.

650 Hz /12 dB is perfect.
 
#1,330
Hello,

My friend Nicolas Davidenko and Frank Delbauve who build Hifi on purpose loudspeakers enclosures, used a 3D CNC to make Iwata-JMLC horns in plain wood.

Here is few pictures of an Iwatat-JMLC (Fc 600Hz, throat diameter = 1 inch).

Le blog de audiobricolos

Direct URL for pictures :

http://img.over-blog.com/300x204/6/15/98/16/iw600-1.jpg

http://img.over-blog.com/300x214/6/15/98/16/iw600-2.jpg

http://img.over-blog.com/300x221/6/15/98/16/iw600-3.jpg

a 1.5inch version used to be build too :
http://img.over-blog.com/500x241/6/15/98/16/iw600-2435.jpg

and a 220Hz Iwata-JMLC horn is under construction.
http://img.over-blog.com/500x356/6/15/98/16/220-2482-3.jpg

2 views of the fproject are at :
http://img.over-blog.com/174x300/6/15/98/16/3voies-1.jpg
http://img.over-blog.com/300x293/6/15/98/16/3voies-2.jpg

Best regards from Paris, France

Jean-Michel Le Cléac'h
 
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#1,333
Are they selling their creations?

Jmmlc said:
Hello,

My friend Nicolas Davidenko and Frank Delbauve who build Hifi on purpose loudspeakers enclosures, used a 3D CNC to make Iwata-JMLC horns in plain wood.

Here is few pictures of an Iwatat-JMLC (Fc 600Hz, throat diameter = 1 inch).

Le blog de audiobricolos

Direct URL for pictures :

http://img.over-blog.com/300x204/6/15/98/16/iw600-1.jpg

http://img.over-blog.com/300x214/6/15/98/16/iw600-2.jpg

http://img.over-blog.com/300x221/6/15/98/16/iw600-3.jpg

a 1.5inch version used to be build too :
http://img.over-blog.com/500x241/6/15/98/16/iw600-2435.jpg

and a 220Hz Iwata-JMLC horn is under construction.
http://img.over-blog.com/500x356/6/15/98/16/220-2482-3.jpg

2 views of the fproject are at :
http://img.over-blog.com/174x300/6/15/98/16/3voies-1.jpg
http://img.over-blog.com/300x293/6/15/98/16/3voies-2.jpg

Best regards from Paris, France

Jean-Michel Le Cléac'h
Click to expand...

Hi Jean-Michel,

Do you know if these guys are selling Iwata horns to the audiophile community?

Kind regards
Kris
 
#1,334
hasselbaink said:
Hi Jean-Michel,

Do you know if these guys are selling Iwata horns to the audiophile community?

Kind regards
Kris
Click to expand...

Hello,

Do you mean classical Iwata horns? In that case the answer is no.

For what I know if there is some demand Frank Delbauve should be able to build Iwata-JMLC in wood
Fc = 600Hz, 1 inch
Fc = 600Hz, 1.5 inch
Fc = 220Hz, 2 inch (build in several parts with 4 parts for the mouth).

But this is not sure and for the moment the only conatct is through Nicolas Davidenko who did the 3D CAO work from the cloud of 40000 points I calculated for him.

To contact him :

nicolasdavidenkoXsfr.fr

replacing the X by the arobase.

Best regards from Paris, France

Jean-Michel Le Cléac'h
 
#1,338
Curve Multiplicity

Charcoal said:
If I want to DIY e-jmlc horn, after simulations in H-resp, how can I draw the curve? Any soft-calculators or something like that?
Click to expand...

It is not a single curve; it is a family of curves that form a mesh (coordinate system), which defines the boundary surface of the horn. If [z] is the horn axis, then in subsequent [x,y] sections leading away from the throat, a circular to elliptical (or oval) transformation takes place where the loci of the major and minor axis are determined by two dependant sets of points using JMLC's method. I will leave other details, including the underlying wave front shape assumption, to JMLC to describe and enumerate.
Regards,
WHG
 
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#1,339
Hello,

All Le Cleac'h horns, the axisymetrical ones, the so called Iwata-JMLC and the E-JMLC are hyberbolic horns by that I mean the evolution of the area of their wavefronts (considered as isophase) follow an expression like:

S = So(cosh(x/xo)+T.sinh(x/xo))²


If we only consider the power response and the directly related parameters, Hornresp can be used to simulate the horn.

Then we have the question of the shape and as William said the shape of the e-jmlc horn is not simply described by a profile.

In fact the excel spreadsheet I wrote to calculate the Iwata horns and the E-Jmlc is more than 100Mo and also the spreadsheet is not so easy to use, so it is not public.

The Iwata-JMLC is more straightforward as it only result from the use of an hypothesis made by Iwata San : the ratio curvilinear width over curvilinear height of the wavefront varies linearly with the distance to throat. Also the perimeter of the wavefront at the wall of the horn is defined as

(x/a)²+(y/b)² = 1

with x and y the curvilinear abscisse and ordinate inside the curved wavefront.
(if you faltten the wavefront, the perimeter of the wavefront is an ellipse)

The e-jmlc assumes other hypothesis...

Best regards from Paris, France

Jean-Michel Le Cléac'h
 
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