Ever think of building a Cornu Spiral horn? Now you can! - diyAudio
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Old 13th December 2012, 10:13 PM   #1
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Default Ever think of building a Cornu Spiral horn? Now you can!

I did. For years in fact, but put it off thinking there was no way my skill level was up to the task. That is, until our good friend xrk971 opened the door to something that is easy for the layman and very rewarding. See this thread:

Foam Core Board Speaker Enclosures?

There is a lot of info in there but it is a good read. The project I did starts at post #101 but I urge you to read it all as there is some good info throughout and lots of learning as you go along.

It's been a long time since a speaker project has been this fun, rewarding and quick. I admit my hopes were not that high to start, but my mind has changed completely regarding the materials used and the overall effectiveness of the project.

They have been coined the 'Cornucopya' Here is a site with the drawing. It is also in the next post.
seb:diy:audio: Cornu Spiral Copy Horn

Enjoy.
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Old 13th December 2012, 10:16 PM   #2
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The sound these produce is beyond my descriptive abilities. They have no business sounding this good.
[Never mind the string of glue on the brass edging in the second pic, it's not a scratch.]

The driver for this is the Fostex FF125WK with all the treatments by planet10.

Mr. Daniel Ciesinger, I am in admiration of your design.

EDIT: There are those who wanted to know more about the foam shaping so I am adding those pics as of December 12, 2013. Starting with the strip of foam pic.

1. Mark where you are going to make your curves
2. Set you knife to about half the depth of the foam
3. Score it freehand about 1/4" or 5 cm plus or minus depending on the radius of the curve
4. Find your rounded surface. Mine happens to be the kitchen counter
5. Form it over by rubbing back and forth and adding a medium amount of pressure
6. The forming will help when it comes time to glue
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Old 13th December 2012, 10:36 PM   #3
xrk971 is online now xrk971  United States
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I have Cal to thank for being an enthusiastic seconder to my build which all started out with an all foam core board (paper faced) design that I wanted to allow me to quickly build new horn designs without cutting any wood. I used the boards that I got from the dollar store, a razor, a ruler, a pencil, and a hot melt glue gun to get started. You can do this project on a kitchen table in a matter of several 2 hour stretches of time. The cabinet I built felt so light and open, my expectations were not high as to the sound. But upon first listen: it wad literally like an epiphany, the trumpets of the heavens sounded ok, maybe that is too much but it was close to that. Anyhow, the sound is almost magical, so ethereal, open, fantastic imaging, full, good bass, great mids and highs, wide sweet spot, and just makes you not ever want to stop listening.
This project has several options: you can pick a size full (75 cm), mini (50 cm), and micro (36 cm). They use circa 5 in, 4 in, and 2 in drivers, respectively. The bigger one takes more time and uses more materials, the mini is a good compromise if you don't want to spend much but still want knock your socks off sound. The micro makes a fantastic bedroom or office speaker. The mini can be built for less than $40 in materials. The sound quality is unbelievable. Finally, the WAF is off the charts. Enjoy!
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Last edited by xrk971; 13th December 2012 at 11:03 PM.
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Old 13th December 2012, 10:36 PM   #4
gpapag is offline gpapag  Greece
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It was about time!
Good move!
Cal, I think that posts of Don Hills and Planet 10 deserve to be copied here too.

George
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Old 13th December 2012, 10:41 PM   #5
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Hi George, I was hoping to get those interested to review the other thread and not duplicate too much. There are so many posts that could be moved over here and there are so many persons who have added invaluable input that maybe we can just let those interested see how it all unfolded over there.

Thanks for your interest, I hope many diy'ers catch the bug. It truly is something to get excited about.
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Old 13th December 2012, 11:10 PM   #6
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Any idea what the veneer is Cal? I looked thru the other thread, but didn't come across anything. They look good BTW.

jeff
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Old 13th December 2012, 11:21 PM   #7
xrk971 is online now xrk971  United States
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Cal used Sureply underlayment, birch. Not veneer.
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Old 13th December 2012, 11:40 PM   #8
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Ok thanks. Looks pretty good for "underlayment".

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Old 13th December 2012, 11:45 PM   #9
Zigis is offline Zigis  Latvia
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How thick is foam board you use? I see few different thickness in shop.
How many boards go to pair of mini or micro? Difficult to understand total length of strips.

how about thous small silver drivers, used in many small Logitech, like this;
Amazon.com: Logitech Stereo Speakers Z120, USB Powered (980-000524): Electronics

I see in local computer shops $10 pair speakers with same drivers, I don't know for sure, they are 2" or even little smaller.
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Old 13th December 2012, 11:55 PM   #10
gpapag is offline gpapag  Greece
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Quote:
Originally Posted by Cal Weldon View Post
I hope many diy'ers catch the bug. It truly is something to get excited about.
When I’ll manage to get back home, this "bug" will be my first speaker experiment in 2013.

My complements to the inventor, xrk971 and you.

George
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