Found this thing at a flea market... - diyAudio
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Old 13th July 2008, 10:54 PM   #1
Fuling is offline Fuling  Sweden
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Default Found this thing at a flea market...

...and I thought it might be useful for molding my own fibreglass horns.
I donīt know if the shape matches any known horn flare but it sure looks good
The throat diameter is 5,2cm, mouth dia. 38 cm and length 22cm.
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File Type: jpg hornform.jpg (17.1 KB, 973 views)
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Old 13th July 2008, 11:26 PM   #2
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I am convinced, that it will perform well.

Many years ago a friend of mine used similar shaped
IKEA lamps in two different sizes, one for the midrange
and the smaller one for hirange. He used the lamps directly
glueing some damping pads on the outside to prevent them
from ringing. He added a baffle around the horn mouth too.

The lamps were driven by Dynaudio units without
pressure chamber, tweeter was D21, midrange don't know
maybe D76 ...

He replaced the mid and tweeter horn of his original Klipsch
corner Horn . He built a decent crossover and got the
new mid-high units out of the corner ...

Useless to say, that the original Klipschorn sounded like
ridiculous crap compared to the IKEA horn ...

Cheers
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Old 14th July 2008, 03:35 AM   #3
GM is offline GM  United States
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Default Re: Found this thing at a flea market...

Quote:
Originally posted by Fuling

I donīt know if the shape matches any known horn flare but it sure looks good.
Indeed! It looks like a mildly truncated tractrix, so should work well with the right driver.

GM
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Old 14th July 2008, 07:02 PM   #4
Fuling is offline Fuling  Sweden
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Thanks!

Iīm working on turning the lamp into a useful plug by adding some MDF parts and lots of Plastic padding filler.
The plan is to make it more "Tractrix-ish" by expanding the mouth slightly, itīs a bit hard to explain but I will post pictures when Iīm done.
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Old 16th July 2008, 03:58 PM   #5
Fuling is offline Fuling  Sweden
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This project is now abandoned, my first attempt went straight to hell and the plug was ruined in the process.
Better luck the next time...
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Old 16th July 2008, 11:03 PM   #6
Fuling is offline Fuling  Sweden
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Success!
This time I used an old horn speaker from the thirties as a plug:
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File Type: jpg fiberhorn 005.jpg (91.3 KB, 591 views)
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Old 17th July 2008, 12:02 AM   #7
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Nice job. Did you use multiple layers of light ( 1 oz.) cloth?
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Old 17th July 2008, 08:35 AM   #8
Fuling is offline Fuling  Sweden
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Thanks!

The horn is still thin as an eggshell, so I will add several more layers of fibreglass + plywood bracings on the outside.
I used light woven cloth to get the throath right and then 10oz mat for the rest.
In retrospective it would have been better to use woven cloth all over.
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Old 17th July 2008, 10:56 AM   #9
AuroraB is offline AuroraB  Norway
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Hi Fuling....

Are you going to use the new cast as a mould for the real things???
For sake of appearance, you should cast the real horns on the outside of a polished mould, - that will give you a smooth inside flare, which is the most visible partof the horn.
I have been thinking about this for quite some time, but neve got around to doing something with it. Some will say fibre glass casts cannot be used doe horns, as they will ring too much....I thinkit is fairly easy to damp the outside, to prevent ringing....cork strips, etc. A few weeks ago I came across a liquid rubber product, used for roofing...( called "Gummitett" in norwegian ).. like thick paint..
Should work OK for damping the outside of the horn, If at all necesseary..........

Nice idea!
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Old 17th July 2008, 02:17 PM   #10
Fuling is offline Fuling  Sweden
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Quote:
Are you going to use the new cast as a mould for the real things???
Hi!

Nope, the cast is the real thing. So far this is very much a "for fun" project just to get an idea of how to do it (and make some noise along the way). Later on Iīm planning to make a plug for a properly designed horn and build something serious out of it.

Using carbon fibre cloth, epoxy resin and proper vacuum techniques would be completely awesome for a project like this, but the materials involved are horribly expensive and vacuum bagging a horn would be a mess...
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