Ever think of building a Cornu Spiral horn? Now you can!

Founder of XSA-Labs
Joined 2012
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Fran,
You have perfect English as far as I can see. :) Your plan for gluing seems good as long as you sand the channels so that they are all even and flat and contact the flat front/back pieces when gluing. I think Sebastian did the same thing and used heavy objects like a bookshelf with books to clamp the boards together while drying. I would use PVA woood glue. For the electrical wiring: with foam core, I just use a sharp tool to poke holes perpendicularly in the channels and run wire through. Note that you can use very thin wire for a full range driver like the FE108Sigma - in fact, many people recommend use of 24 gauge solid copper strands taken from inside a Cat5 networking cable. Two of those strands is enough and all you have to do is take a sharp razor and cut tiny little notches along the top edge of the channels to fit the wires in place. Then use hot melt glue to secure the wires in place on the notches and to make a good seal. Then when you glue to back panel on the wire will rest between the panel and the channel edge. Mount speaker cable binding posts (drill thru hole types) on the last channel wall and connect the wires to the inside terminal pins and you are done. Alternatively, Cal and others have just made a large cutout for a recessed cup type binding post holder for the wires right at the driver chamber (centrally located). Personally, I would go with the thin wires and notches to have binding posts on the bottom outside edge of channel so that the wires don't hang from the back of the speaker which allows it to mount flush against the wall.
 
Hi X, I agree with you!
I'd prefer to have the binding posts located at the bottom of the speaker. I drilled a couple of holes for them on the middle plate, at the bottom of it , outside the spirals.

http://fperezroig.files.wordpress.com/2013/03/dsc05452.jpg?w=223&h=298

Thanks for the tip about the UTP cat5 cables and the notches!! That's definitely the way to go!! I'd have never thought that a couple of those thin cables would be a good idea. Why is it that you mentioned the specific fe108ez to be appropriate to use with thin wires?
 
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Joined 2012
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If you spend enough time on this forum you will see that people will recommend this setup for not only the FE108Sigma but all high efficiency full range drivers. First of all, the power requirements are rather low, and amps are not that high, and there are technical reasons like the added resistance is good for the damping factor, etc. Planet10 and others can give you the citation to the research behind this. Main reason I do it is thin and convenient and low cost. I have also used 4-solid conductor 22 awg in a white sheath for a stereo setup. That works well because the thin white sheath blends in well with walls. I sometimes double the 22 awg wire to get more current.
 
Hi Guys- Happy Saint Patrick's Day :D
I lucked out a couple days ago and found a Bose SR-301 stereo for $3 at the thrift store. The drivers are destined for a new Cornu built. They are 2.5" (65mm) in diameter 4omh, 3W. I am guessing a size of 14" square by about 2" deep. :confused: Would that be the right size?
Here they are

Thanks for all your help!
 

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Hey guys!

I just thought about a neat idea in the other foam core thread. Since vibrations appear to be one of the central issues of foam core, has anyone thought about damping vibrations with a liquid damper? You could possible apply it to the interior and exterior of the cornu.

DEI 050220 Boom Mat Spray-on : Amazon.com : Automotive

When I get around to making another set of cornu spiral horns, I will coat them with a spray like this. If anyone is making a set at the moment though, I encourage you to give this a try and report your findings! The main issue that we've discussed is that it might be petroleum-based and may dissolve the foam, although this spray appears to be mild.
 
Hey guys!

I just thought about a neat idea in the other foam core thread. Since vibrations appear to be one of the central issues of foam core, has anyone thought about damping vibrations with a liquid damper? You could possible apply it to the interior and exterior of the cornu.

DEI 050220 Boom Mat Spray-on : Amazon.com : Automotive

When I get around to making another set of cornu spiral horns, I will coat them with a spray like this. If anyone is making a set at the moment though, I encourage you to give this a try and report your findings! The main issue that we've discussed is that it might be petroleum-based and may dissolve the foam, although this spray appears to be mild.

I can't imagine how this stuff would work in this situation.
 
Hi there!
Finally wired the cabinet and glued the back plate and everything seems to be ok!! Used an utp twisted pair like you suggested, and both wires go through the spiral after cutting some small notches on top of it. This way couldn't be easier!! I'm really happy with the result and did not need to drill a single hole.

Each cable measures around 1.2ohms, hope this is ok.
Thanks for all your help!! Hopefully the enclosure will be finished this week and ready to be lacquered! I'll keep posting some updates.

Kind regards,
Fran
 

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