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:

http://www.diyaudio.com/forums/full-range/223313-foam-core-board-speaker-enclosures.html

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.

Here is a post from member palmiepaul, summarizing the project before even starting to build. It is recommended reading.

http://www.diyaudio.com/forums/full...u-spiral-horn-now-you-can-49.html#post4153092

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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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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Founder of XSA-Labs
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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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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.
 
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.
 
Founder of XSA-Labs
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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.

It is 3/16 inch thick - if There is a Dollartree in Latvia, they have only one thickness. The z120 you suggest would even be better than the s120's I used. The strips you cut as you need but for the micro it was like about 8 x 30 in long strips. You need to join them in segments, can't have one that is long enough. It takes about 3 sheets of 20 x 30 in sheets for the micro, and 6 sheets for the mini including faces. Let me know how the z120s are mounted, if tbere is no flange with screw holes you will have to glue it in place and that is a bummer as you can't tweak and adjust the stuffing.
 
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Founder of XSA-Labs
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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

George,
Thank you for the kind words but the inventor is Daniel Ciesinger, I am just a guy who likes to make things in a hurry and am handy with a hot melt glue gun ;) I think I showed folks that it is possible to make a good sounding speaker without having to use heavy dead sounding MDF, or having to spend countless hours in the workshop to leave a speakerwidow behind. When building speakers doesn't require a tablesaw, a router, a drill press, or a shop vac, I am all for it. It was borne out of necessity because at the moment I don't have access to power tools or a shop, so I had to keep myself busy somehow. I think there are a lot of DIY'ers out there in a similar situation whether they live in a small apartment, or just don't yet have a workshop, that shouldn't stop them from making or trying out new speaker designs.
Regards,
Xrk971
 
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Coir is a fiber and would probably work well as stuffing in a speaker. The coconut shell, however, would probably make an excellent speaker cabinet as it is spherical and you would minimize diffraction or baffle step effects. A 6 or 7 in dia coconut would probably be suitable as a HT speaker with a 3 in FR driver in a sealed coconut cabinet stuffed with coir:) It would really look good if your HT room was decorated with an island theme! :D
 
catch the bug.

Cal,

I appear to have, despite my dislike of horns, all thanks to you.
(maybe because it's not a folded horn, not a single horn exit opening/location, Hey ! And so flat)

Any reason for using use the FF125WK, instead of Mr Ciesinger's FE108E Sigma, other than half cost and availability ?

(and don't believe everything Mr Papageorgiou writes)
 
I've been following the spiral concept through various posts on different thread and through Google searches. Conceptually it is a really elegant idea !
I have a few questions.

1. Is there any math behind it to scale to different drivers(Lowthers). On my searches I did find a person who used a Lowther Driver.

2. How much Low frequency enhancement will this horn will support ?

As crazy Idea ... How feasible is it to mount a front horn to it ? Since the speaker is a nice square ...For inspiration, maybe a horn similar this (post 54) Can be grafted to the spiral back loaded horn ? :
http://www.diyaudio.com/forums/full-range/162861-i-want-these-12-field-coil-ebay-6.html


To bad I just started a different horn project .. this seems very interesting
 
Founder of XSA-Labs
Joined 2012
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I've been following the spiral concept through various posts on different thread and through Google searches. Conceptually it is a really elegant idea !
I have a few questions.

1. Is there any math behind it to scale to different drivers(Lowthers). On my searches I did find a person who used a Lowther Driver.

2. How much Low frequency enhancement will this horn will support ?

As crazy Idea ... How feasible is it to mount a front horn to it ? Since the speaker is a nice square ...For inspiration, maybe a horn similar this (post 54) Can be grafted to the spiral back loaded horn ? :
http://www.diyaudio.com/forums/full-range/162861-i-want-these-12-field-coil-ebay-6.html


To bad I just started a different horn project .. this seems very interesting

If you go back to the foam core thread, there are several posts by Don Hills whom is modeling this on Akabak, he also gives an outline of how to design one from scratch with the driver of your choice. So, I think you can design this for Lowthers. I think this horn will make an alredy efficient driver even more efficient. One of the things that the Cornu has is very high efficiency of horn output.

Regarding the front horn: Yes - in fact, Cornu (the company making these) offers wooden 8-segnment horns that can be strapped to the front of the driver. I look at this and see perfect opportunity to make the front horn out of foam core board too - and you could make it perfectly curved rather than use flat segments.

The bass or low frequency enhancement question has been asked severral times before. All I (and Cal) can say is that it has a huge impact based on listening to it. I was fiddling with the cable mounting hardware on the back of the Cornucopya yesterday while it was still playing music, and flipped it on its face on the carpeted floor and I still heard a significant amount of music coming out of the edges through the horns (mid bass, low bass, and actually quite a bit of highs - which is not unexpected given how there are few sharp corners to act as low pass filters). This gave me an idea of an easy way to demonstrate how significant the horn output is. Flip it on its face on carpet so all sound comes from horns - record this with good mic to mp3. Flip it around and record sound with both, and post this so you all can listen for yourselves. Note that this is very different than how it sounds on a wall as the ceiling and floor interaction is important. But it will give an A/B test of the difference with and without front driver output.