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Old 29th September 2008, 06:52 PM   #11
AKN is offline AKN  Sweden
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Hi,

Elbert and AuroraB,
PM me and I'll return a PDF copy from the corresponding articles.

My time is limited this evening but I'll sure come back to this thread later this week.

(Hornresp sim would be great)
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Old 29th September 2008, 07:24 PM   #12
tinitus is offline tinitus  Europe
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Default Re: Re: Bass horn driver?

Quote:
Originally posted by Jmmlc
Hello,

In the attached picture you'll see the (Le Cléac'h) bass horn built by my friend Frédéric Lebas.

Best regards from Paris, France

Jean-Michel Le Cléac'h


Thanks Jean, thats a brilliant idea I would like use
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File Type: jpg floor horn.jpg (50.9 KB, 809 views)
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Old 29th September 2008, 07:39 PM   #13
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Just a little bit of inspiration of the horn(y) kind. http://www.faktiskt.se/modules.php?n...rticle&sid=179

NOT my system.
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Old 29th September 2008, 08:11 PM   #14
AuroraB is offline AuroraB  Norway
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At least partly OT....I think this one has been linked before...
http://www.royaldevice.com/custom.ht...20TOTAL%20HORN


Well.... some like it BIG
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Old 29th September 2008, 09:51 PM   #15
Elbert is offline Elbert  Norway
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Lord have mercy... that looks like the acoustic equivalent of the great halderon colider...


I guess I'll settle for some good punch below 40Hz at realistic listening room levels, seems such a humbe goal now by comparison!
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Old 30th September 2008, 08:16 PM   #16
Elbert is offline Elbert  Norway
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Default back to the problem..

Now, back to the challenge of modeling the RT-2 horn in Hornresp...

The throat area of the horn is pretty straight forward, it equals the diaphragm area..

Then there is the challenge of figuring out the mouth area.. I guess one could just take the physical dimensions of the opening as it apears between the body of the horn and the wall/floor.

however, the theory behind this design is based on the effective mouth-area being double that of the physical area due to reflection off the floor.

The approximative length can be taken by making measurements of the construction drawing...

But the big question is still; what is the exponential ratio used?? Since the original profile is approximated by straight sections, figuring out the original exponential profile will be tricky..

Heck.. this is going to be a bit difficult...
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Old 30th September 2008, 08:31 PM   #17
GM is offline GM  United States
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Seems like a better approach is to design a new horn with a current driver to fit in ~the same bulk...........

GM
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Old 30th September 2008, 08:58 PM   #18
Elbert is offline Elbert  Norway
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GM, you are of course correct...

But it seems I'm making some headway here...

Based on my method of assumption described earlier on, I

modelled a horn with a throat area of 570 cm2, length of 216 cm, and mouth area of 6820 cm2 with an exponential contour.

Acording to Hornresp. that should give a flare cut-off of 30 Hz.

This is allso the stated cut-off frequency of the RT-2 horn!

I did the model with the pioneer driver, and the SPL curve is not too unfamiliar to those measured at the mouth of the original horn.

Now, here's the exiting bit... one of the drivers tested with the original horn was a JBL 2202. As opposed tho some of the other drivers that were used, this JBL should have some available parameters..

So next step is to dig these parameters up, plug in to horn resp and see if the curve resembles the one measured 30 years ago!

To be continued...
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Old 30th September 2008, 08:59 PM   #19
GM is offline GM  United States
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Anyway, to answer your Q, find the throat and mouth cutout area and the acoustic path-length between the two, then use an expo calculator to find the flare frequency that fits the length.

GM

Oops! I see you've already posted this.........

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Old 30th September 2008, 09:24 PM   #20
Elbert is offline Elbert  Norway
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Well, the simulated JBL curve and the measured response from the magasine had some diferences, but nothing wild..

The measurement was actually a bit smoother and had slightly better low frequency extension.

But it looks close enough to at least partially validate the horn model in Hornresp.

Heck.. haven't quite figured out how to save or export the frequency response plot..

When i get my head round it, I'll see if I can post the calculated and measured curves here!
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