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Old 10th December 2012, 07:18 PM   #551
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Quote:
Originally Posted by ikoflexer View Post
On page 3 of the patent in paragraph 0021 it describes the cone (5) from Fig. 1 roughly as an outward deflector of the sound waves. Perhaps that's actually important.
I can say that all of Scott's double-mouth horns and BVRs have a similar bit in them at the bifurcation of the horn, see attachment.

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File Type: gif kirishima-deflector-detail.gif (48.5 KB, 474 views)
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Old 10th December 2012, 07:28 PM   #552
iko is offline iko  Canada
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I'm trying to make sense of the script and add that in the simulation. Should have some effect.
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Old 10th December 2012, 09:27 PM   #553
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thanks for the kind words guys, dont worry badman, it has the lid tightly attatched now

XRK, ill be sure to get a short MP3 of the sound either today or tomorrow for ya, its gonna be the upload that kills me, havent exactly got a fast connection available to me at the moment...

and thanks Cal. im rather pleased with it. im even thinking about just cleaning up the glue joins and leaving it as card finish.. maybe.
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Old 10th December 2012, 11:43 PM   #554
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Quote:
Originally Posted by ikoflexer View Post
I'm trying to make sense of the script and add that in the simulation. Should have some effect.
In the spirit of this thread... If I take an arc shaped strip of foam core and score it radially outwards from the inner edge of the arc to the outer edge of the arc, the carefully bend it and close it on itself, then fasten it with hot melt... I might be able to build a cone. Hot melt that into place and check it out. Another idea is to use the plastic nose cone from a model airplane propeller. Any other ideas where to find an easy cone to try? My problem is that my Cornu is rather shallow and may not allow much room compared to the 4.5 to 5 in deep ones that seem to come with the full size ones.
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Old 10th December 2012, 11:46 PM   #555
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Quote:
Originally Posted by ikoflexer View Post
I'm trying to make sense of the script and add that in the simulation. Should have some effect.

Iko, are you well versed with Akabak? I believe the cone will improve efficiency, but I don't think it will have much of an effect on the horn resonances, peaks and dips, that Don Hills pointed out in his sims. Interesting to see how it works though. How do you plan to implement the cone in the script?
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Old 10th December 2012, 11:58 PM   #556
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The horn of a rear-loaded horn speaker is mostly for bass reinforcement - you don't want HF coming out of the horn. The cone-shaped deflector will tend to make the HF problem worse by reflecting more HF into the horn mouths. It won't help the bass at all because the wavelengths are too long compared to the dimensions of the cone. Also, the cone will reduce the volume of the back chamber. This will have to be factored into the rear chamber dimensions.
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Old 11th December 2012, 12:06 AM   #557
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No, I've never seen akabak before in my life. That's probably why the simulation results don't make sense to me. The script uses conical horn elements. I don't know if in akabak a cone is a real cone, meaning that it is a circle in cross section. The real horn of the cornu is not a real cone. It's a pyramid. I can't really comment until I learn akabak.

That cone at the back of the driver, if it's not there, you can obviously see that the sound waves hit the opposite wall and some will come straight back to the driver, no? To me it makes common sense to have that cone in there. Is my common sense so far off?
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Old 11th December 2012, 01:21 AM   #558
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"Conical" in AkAbak means that the area increases as the square of the length. It doesn't matter if the cross-section shape is circular, elliptical, square, rectangular, octagonal etc, provided that the longest dimension across the cross-section is significantly less than 1/4 wavelength at the frequencies of interest.
Flat-walled horn with 4 straight walls, all diverging = conical profile.
Flat-walled horn with 4 straight walls, 2 diverging, 2 parallel = parabolic profile.
For horns with small rates of divergence (taper), such as the Cornu near its centre, the profiles are almost identical. They differ more at the mouth, where the divergence increases rapidly.

Actually, a true Cornu / Euler spiral curve horn built as a spiral between 2 parallel plates more closely follows a conical area rule than a parabolic area rule. If you imagine it "unrolled" into a straight horn, the walls are not straight - they curve away from each other.

Regarding the cone behind the driver, if common sense was (common), the world wouldn't be in the mess it is. Look at it this way: Most of the HF reflection through the cone occurs from the driver frame/magnet and spider. A cone behind the driver would only be useful if there was nothing between the back of the driver's diaphragm and the cone. Because of the shadowing effect of the driver's rear parts, the cone would also have to be significantly larger diameter at its base than the driver in order to have any effect. Finally, if you did have a cone, the reflected energy would just bounce off the chamber walls, back off the cone and up through the driver. Replacing the cone with an equivalent volume of stuffing would be more effective.
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Old 11th December 2012, 01:29 AM   #559
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First, a thanks to Don Hill for all his input. I don't have to understand it all to know how valuable his input is here.

Quote:
Originally Posted by klampykixx View Post
im even thinking about just cleaning up the glue joins and leaving it as card finish.. maybe.
You saw how easy it was to dress it up with a little veneer, trim pieces and grill cloth. Go for it.
Quote:
Originally Posted by Don Hills View Post
The cone-shaped deflector will tend to make the HF problem worse by reflecting more HF into the horn mouths. It won't help the bass at all because the wavelengths are too long compared to the dimensions of the cone. Also, the cone will reduce the volume of the back chamber. This will have to be factored into the rear chamber dimensions.
All of this make sense. I am am glad someone in the know said it.
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Old 11th December 2012, 01:37 AM   #560
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I'm not a speaker designer. I've never even played one on TV. It's just my common sense, of which I have precious little.
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