Jean Michel on LeCleac'h horns

Jmmlc said:
Hello Soongsc,

T is a coefficient in the general frouma linking the area and the distance to throat for horns of the hyperbolic family

http://www.bd-design.nl/contents/media/hypo.gif

T = 0 : catenoidal horn
T between 0.5 a,d 0.707 : hypex horn
T = 1 : exponential horn
T infinite for conical horn.

Best regards from Paris, France

Jean-Michel Le Cléac'h
Thanks Jean-Michel,
I'll try to figure things out.



 
hello Jean Michel

thanks for your answer. Interesting, your mention of Onken drivers. In the past, there where a few offers at ebay and some places elsewhere, and i was curious to try them out, since these seem to have been built only for home / high-end use - but hesitated , because of lack of information on the web in regard of their performance, specially comparing to other drivers.

There is a ongoing debate for a long time already on various forums about different horn / wave guides, each one claiming and advocating that this or that is best. You have a lot of advanced theoretical answers , why in your opinion the LeCleac'h profile performs better, and avoid setbacks generally attributed to horns. My most important concern was always to get the most fidel/natural sound, without horn coloration and honk, but also without have to miss dinamics. Only horn systems can deliver that live like sound, which amazes me. In the past, and more intensively in the last 3 Years, i have tried out a number of drivers and different horns and setups at home. The best i have come up until now is my actual configuration, using in the midrange a LeCleac'h horn, and Vitavox S2 driver. While it does reproduce most music incredibly well, beeing it a real pleasure and relaxing, to spend time, listening to music, there are other things, that i wish, it would do better. Namely voices, specially female voices, have the tendency, sometimes to sound irritating. And there is also a high degree of directivity , and little move of listening position, changes the presentation dramatically ( thats less of a concern for me ). After i compared with the Audax Medomex , ( even not well integrated in the system ) , but in a closed, apropriate box, crossed same as S2, it became clear to me : the Medomex sounds far more natural/neutral - and as conclusion : there is still a far way to go, to come close to the performance of a direct radiator, when the main point of observance is neutrality/timbre/tone. After your post at AA, i played around with different crossover points, trying to improve things, but the existing configuration was best. So: whats the reason the Medomex is more natural ? is it the compression driver ? the simple first order crossover ? no linear power response ? or in the end the horn shape ? What other factors could it be, than mouth diffraction, HOM's , unsmooth transmission from driver to throat etc ? I once asked you, it it might be, that the shorter the horn, the less honk ? u said no. But this is getting to be something, i start more to think about. I suspect that main cause of horn honk and coloration is coming from the first exponential part at the throat with small opening. A horn with fast opening looses its function, turning just into a waveguide with directivity control. Than dinamics goes away as well.... In the final, the conclusion : whatever we do , it is always a compromise....

Angelo
 
Now that we have a new thread, here's the latest BEM eye candy from Bjorn Kolbrek in Norway. The first example you've seen before in the Onken thread, it's an AH425 with a 288 driver - cutoff frequency 425 Hz, T = 0.707, 1.4" exit diameter and 8 degree flare from the compression drive. Phase plug HF cancellations and diaphragm breakup are not simulated.

The AH425 is a 16.5" wide horn with a nominal 425 Hz cutoff, and usable (resistively loaded) frequency response down to 550~600 Hz. In practice, a 800~900 Hz crossover is recommended to avoid the region with sharp group-delay variations.

BEM at 1 kHz:
 

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Now this is where differences start to appear. The graph shows the power factor of the two horns. The heavy lines are for the standard AH425 with a T = 0.707, and the thinner lines are for the T = 1.34 version.

The red lines show power reflected back to the diaphragm (as a percentage), while the black line shows the power radiated into the room. (Similar to SWR of an antenna.) Ideally, the load on the diaphragm should be purely resistive in the audio range for maximum power transfer and minimum reflections. It was JMMLC in private communication that made the connection between resistive loading and a smooth group-delay response - something I had not considered before.
 

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For another power factor comparison, here's a comparable-size conical horn (with no radiused edges on the mouth) with a 288 driver. The red line is the reflected power, while the green line is power radiated into the room (as a percentage). As before, these are idealized drivers with no departure from flatness due to the phase plug cancellations or diaphragm breakup. Most of these departures, though, happen at the top of the audio range, where the power factor comparisons between different types of horn converge.

Many, many thanks to Bjorn Kolbrek for all of the many simulations that went into the AH425 - what you see is only a small fraction of the graphs I've been seeing over the last several months. And many thanks again to JMMLC for doing the work he's done.
 

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Jmmlc said:
Try different values of the diameter, T coefficient and Fc until you reach the desired angle.

Hi soongsc,

Hornresp shows the throat flare tangent angle as parameter AT on the main input screen.

S1, F12 and T values for a Le Cléac'h horn can be changed and the effect on AT seen immediately.

Le Cléac'h horn profile data can be exported from Hornresp.

Hope this helps.

Kind regards,

David
 
David McBean said:


Hi soongsc,

Hornresp shows the throat flare tangent angle as parameter AT on the main input screen.

S1, F12 and T values for a Le Cléac'h horn can be changed and the effect on AT seen immediately.

Le Cléac'h horn profile data can be exported from Hornresp.

Hope this helps.

Kind regards,

David
Hi David,

The throat section compresses and expands, and consists of multiple types of curves, part of which Le Cléac'h horn type expansion might be used, it seems not possible to do in Hornresp. Currently I try to get the data of curves contiguous, then look at the BEM results to see how overall wave expansion looks like.
 
Hello,

The large horns belong to a friend of the association Mélaudia. He got them quite recently. It was a special order to an enclosures builder.

I only knows that 3 channels digital filtering will be done under Foobar v8

Best regards from Paris,

Jean-Michel Le Cléac'h


pk said:
Hi Jmmlc,

Thanks for sharing all the knowledge regading your horns!

I have a question regarding the system that according to your post above will be demonstrated ultimo March:

http://www.melaudia.net/rueil0903.php

Could you please specify the crossover points of this system?

Thanks!

Best regards
Peter
 
Soongsc, more data is needed. It would be nice if the pictures weren't so tiny (being able to read the frequency would be very useful), and there were 3 dB plotlines on the contours to get an idea of the actual magnitude of the falloff with angle. JMMLC horns are not constant-directivity, so the degree of falloff is useful to know.

Without magnitudes, frequencies, knowledge of the horn profile, or diameter of the throat, the pictures don't convey much information. If the simulated driver is a physically unobtainable compression driver with zero throat length, that alone throws off the simulation.

If you have access to the original data, I'd take advantage of the DIYAudio 1000 x 1000 pixel limit and post them one by one.
 
Hello Angelo,

From my own experience and friend's one, the S2 may be a bit harsh or fatiguing sometime.

I know quite well the Medomex (this is a French loudspeaker from the 60's and 70's and even I have a pair at home - but suspension is worn now). They are good medium loudspeakers but I will never used them in my main system.

Best regards from Paris, France

Jean-Michel Le Cléac'h


angeloitacare said:
hello Jean Michel

The best i have come up until now is my actual configuration, using in the midrange a LeCleac'h horn, and Vitavox S2 driver. While it does reproduce most music incredibly well, beeing it a real pleasure and relaxing, to spend time, listening to music, there are other things, that i wish, it would do better. Namely voices, specially female voices, have the tendency, sometimes to sound irritating. And there is also a high degree of directivity , and little move of listening position, changes the presentation dramatically ( thats less of a concern for me ). After i compared with the Audax Medomex , ( even not well integrated in the system ) , but in a closed, apropriate box, crossed same as S2, it became clear to me : the Medomex sounds far more natural/neutral - ....

Angelo
 
Well, I abused the images in Photoshop and Genuine Fractals, and this was the best I could do. At 3X enlargement, the horn appears to have zero throat diameter - although that would certainly give nice HF dispersion (at 22 kHz!), it would also seem a bit unrealistic.

No apparent throat depth either - is the compression driver assumed to be a point source? That might be valid for an Ionovac or the Acapella ionic driver, but for physical compression drivers with physical diaphragms ...
 

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Jmmlc said:
Hello,

The large horns belong to a friend of the association Mélaudia. He got them quite recently. It was a special order to an enclosures builder.

I only knows that 3 channels digital filtering will be done under Foobar v8

Best regards from Paris,

Jean-Michel Le Cléac'h




Hello Jean-Michel,

Thanks for your reply!

Best regards
Peter