Cornu Spiral Copy Horn

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Well hello again everybody :)

I posted a while ago (the original post is here), asking for advice in choosing a project to go with a T-Amp. I had a lot of nice replys, and even decided on a project in the end (thanks again to everybody). But then i stumbled on the Cornu Spiral Horns, and lost all logical reason. I just fell in love with their looks.

Well, two months (and a lot of sleepless nights) later, here are the results :

An externally hosted image should be here but it was not working when we last tested it.


They are 70 x 70 x 16 cm in size, and house the Monacor SP-50X drivers. Everything is in lacquered wood, and glued together (no bolts or other).
They produce more bass than i would have asked for, and sound just wonderful (but lack some mids with vocal stuff) with the modded T-Amp, that in turn amplifies an iPod. As the T-Amp got 5 new caps in it (Black Gate & Elna), i presume that they'll take some time to settle in and will even out the sound over time. I don't know if the Monacors need to be "driven in" the same way ? In any case i'm wildly happy with them, and am sure that by carefully placing them will find the "perfect sound" for me (that already happens with certain tracks, mainly electronic) :)

I just wanted to keep you updated on my project as i promised you to do, and should you wish to find out more details (and many photos) about the project, i made a small blog around my few diy adventures to date (i'll still have to add a page about headphone amps). You can find it here -->
http://sebastian-pitkanen.blogspot.com/

Cheers again, and here's a few more pics : :wave2:

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 
hersh,

Nice work! I didn't realize those things had 2 spirals for each speaker. That really is a lot of work (beers). l love the mouth spread all around the sides and I'm planning to use that approach for some very compact floor-standers. It sounds almost like the horn portion is a little more efficient than necessary, which is good news for me as my total horn volume will be quite a bit less than yours

I do have a question about the sound. Do you feel that the sonic projection via the horn being all around the speaker lead to a larger sounding image than a normal speaker? ie How big do they sound in relation to that small driver?
 
Thanks guys :)

johninCR said:
I do have a question about the sound. Do you feel that the sonic projection via the horn being all around the speaker lead to a larger sounding image than a normal speaker? ie How big do they sound in relation to that small driver?

I sure do feel it. The sound is clearly projected all around, and gives it this "airy" impression. They do have a particular sound in this respect, a "presence", that floats around. And they do sound *big*. That, yes. Really. But i'm not really in the best of conditions with them yet, as i've still to place them ideally.

I think to swap for the FE108EZ drivers in near future, which Daniel said sound dramatically better. I can only imagine the results :hphones:
 
I've got 4 pairs of 108EZ. So far one pair OB with bass augmentation that sounds great, just can't apply more than a few watts. Another pair in the recommended Fostex horn, which sounds really nice, just not enough of that true single driver sound with the horn mouth facing forward. I'll do a set of the Frugel horns once more builds are done and the group has it fully tweaked, so once I build my Tombstone design I'll have a lot of comparisons. Your report of the large sound is very encouraging that I'm on the right track with my latest plan for the Tombstone with the horn mouth around the sides and top of the cab.
 
Hi

Nice work :)

Did you calculate the horn layout yourself or did you copy it from a photo?

I made a "simple layer" a while ago (micro-io.dk) ... But is the two-layer better ? the extra plate might stiffen the thin walls, but i think the only reason that cornu made the layer in the middle is that it is easyer to produce, as it only has one spiral that holds the spiralwalls. In the "simple-layer" the spiralwalls has to fit the spiral cutout in both top and bottom.. and that is nearly impossible!

The Cornu and your speaker has a chamber that starts with a horn split in two and at a later point is split into two again, this will make the lenght off one half off the horn a longer than the other half. Is this notisable in the sound ?

Best regards

Kim Olesen
 
Hi guys - I guess this topic is still active even though it has been awhile since anyone posted.
I have viewed and read a lot on the Cornu Spiral and its derivatives (on this site and elsewhere) and have found 2 versions. Can anyone tell me please, why the difference between the two designs of spiral horn. One (the original version I believe), has 4 spirals, whilst the later model has a center plate and 8 spirals - albeit those 8 are half the depth of the 4. Was this 8 horn version designed to 'ease' construction, or was it a fundamental update to improve upon the sound qualities?
I am considering taking up the router and undecided which version . . . . 4 or 8 horn . . . .. !
cambshiregordon
 
Router Bit Suggestion

Great work! This idea has always intrigued me. I saw the construction and immediately thought of the router bits I bought to build my cedar strip canoe. They would greatly simplify the construction of the tight corners.
 

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italynstylion said:
What wood is used to make these that can bend like that without being kerfed? That bends down to quite an impressive radius!
It looks like 'bending plywood' -made with luan-type wood, with the plies arranged to allow bending along one axis of the sheet. Available in 4x8 sheets, and you need to specify which way you want the sheet to bend- there are two varieties.
You can laminate two layers together if necessary to get a stiffer panel.
It's used quite a bit in built-in furniture projects like bars, etc with curved ends, so should be available if you ask around.

Cheers
John
 
italynstylion said:
What wood is used to make these that can bend like that without being kerfed? That bends down to quite an impressive radius! Also, is the wood for the front of these the same as the inner portion? I need to find some plans for these. They look awesome!


I think the rear and the inner panels can be of a wood such as birch, but the font panel could be a more decorative wood of your choosing. A more dense hard wood would make the final loudspeaker a lot heavier, but I would not expect it to compromise the 'sound' -- rather it may help acoustically by deadening any vibrations.

Apart from the forum posts on this site, below are the web pages that I found interesting when I was investigating this design -- hope they may be of use to you.

http://sebastian-pitkanen.blogspot.com/2006/07/cornu-spiral-copy-horn.html

http://www.freewebs.com/ulzog/poiramsspiralhorns.htm

http://www.diyparadiso.com/cornu1.htm

http://www.fostexinternational.com/docs/speaker_comp/pdf/fe108ez.pdf

http://www.6moons.com/audioreviews/cornu/cornu.html

http://stickynotes.spaces.live.com/Blog/cns!1pRV72pzHktkcUpfy8CdkZ6w!204.entry

http://blogs.msdn.com/andrewdelin/archive/2005/12/29/507944.aspx

http://www.diyaudio.com/forums/attachment.php?postid=1720239&stamp=1232593757&


Regards. cambshiregordon
 
Perspex front?

italynstylion said:
Also, is the wood for the front of these the same as the inner portion? I need to find some plans for these. They look awesome!

Italynstylion

The spiral horns may look good with a 1 inch perspex front - take a look as the sides of this speaker! This would allow your woodworking skils to be on display!

http://gallery.audioasylum.com/cgi/gi.mpl?u=7324&f=C_Horn_timber.jpg

cambshiregordon
 
Re: Perspex front?

CambshireGordon said:


Italynstylion

The spiral horns may look good with a 1 inch perspex front - take a look as the sides of this speaker! This would allow your woodworking skils to be on display!

http://gallery.audioasylum.com/cgi/gi.mpl?u=7324&f=C_Horn_timber.jpg

cambshiregordon


Indeed. It would be quite a bit heavier though. I'm still trying to figure out how assembly on something like that works. I'm imagining the bent pieces of wood wanting to spring back into their original shape and it being a complete catastrophe.
 
Ex-Moderator R.I.P.
Joined 2005
Re: Re: Perspex front?

italynstylion said:



Indeed. It would be quite a bit heavier though. I'm still trying to figure out how assembly on something like that works. I'm imagining the bent pieces of wood wanting to spring back into their original shape and it being a complete catastrophe.

For the spirals use something we in the UK know as bendy mdf. See these links for the idea -

http://www.pbplywood.co.uk/finsa-bendy-mdf-long-grain.html
http://www.d3uk.com/products/bendymdf.html
http://www.lathamtimber.co.uk/ProductDetail.336.html
http://catalogue.chilterntimber.co.uk/product1240625catno370625.html

cambshiregordon
 
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