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Old 12th March 2009, 02:05 AM   #21
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by tinitus
I know this is approved
I hope they don't have animals running around Nice place to hide.
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Old 12th March 2009, 02:08 AM   #22
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by Jmmlc
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.



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Old 12th March 2009, 04:15 AM   #23
Pano is offline Pano  United States
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Quote:
Originally posted by soongsc
I hope they don't have animals running around Nice place to hide.
Just play a little Wagner or Jean Michel Jarre. Animals all gone!
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Old 12th March 2009, 05:02 AM   #24
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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
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Old 12th March 2009, 05:54 AM   #25
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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:
Attached Images
File Type: gif ah425_field_1k.gif (40.1 KB, 3661 views)
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Old 12th March 2009, 05:55 AM   #26
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Same AH425 and 288 as before, this time at 6 kHz:
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File Type: gif ah425_field_6k.gif (56.3 KB, 2418 views)
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Old 12th March 2009, 05:59 AM   #27
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One only thing is changed here: the T ratio is set to 1.34, which yields a different horn profile. Everything else is the same as before ... 288 driver with 8-degree internal flare, 425 Hz horn cutoff, etc.

Frequency is 1 kHz:
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File Type: gif ah425_288b_t134_field_1k.gif (91.7 KB, 2372 views)
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Old 12th March 2009, 06:00 AM   #28
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As before, this is the T = 1.34 variant, this time at 6 kHz. As you can see, there is very little apparent difference in the BEM simulation - I expected a difference in dispersion, and if it's there, it's not very obvious.
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File Type: gif ah425_288b_t134_field_6k.gif (95.0 KB, 2316 views)
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Old 12th March 2009, 06:04 AM   #29
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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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File Type: gif ah425_288b_t071vst134_pf.gif (5.9 KB, 2406 views)
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Old 12th March 2009, 06:40 AM   #30
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by panomaniac


Just play a little Wagner or Jean Michel Jarre. Animals all gone!
It's what they leave behind that worries me.

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