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In the Forum: Horn-Loaded Speakers
In the Thread: Macondo’s Midbass Project – the grown up time.
Post Subject: Possible option for fabricationPosted by Albert on: 6/26/2010
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The top 3 are to scale model of the throat, mouth and length you posted above without the horn profile.
the bottom image is the equivalent flat pattern.
If you were to cut the pattern out of material and sow the sides together, add a circular frame for the throat and a triangle frame for the mouth and pull it tight you will have your horn shape with a perfect transition from round to triangle along the entire length of the horn. paint or spray this in resin and when it sets you will have a mould. Then cast your cement or plaster around this.
If you use a meterial that is non stretchy then you will get an accurate reproduction of your profile within, at a guess, +- 1cm of design profile.
I have cast things out of sand and glue and it sets very strong. Just basic wood glue sets very strong but there are of course much stronger glues available. the right glue and sand would have stronger tensile strength than cement, with comparable compressive strength. Adding some fibers to the mix would increase strength again. Jessie would know what would be best for that. any comment Jessie?
Not to mention you would end up with the surface finish you go for.
you could stand the mould on its mouth with the throat sticking up in the air and pack the sand/glue slurry around it doing it in multiple stages, working from the bottom up. i guess this way you would need something to tie each stage together much like reo bar does for cement. Alternatively you could build an outer mould to hold the mix against the inner one and cast it all in one go.
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