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Old 3rd March 2005, 06:35 PM   #1
Piper is offline Piper  England
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Post My exponential Horn

Just thought i would show you guys the horn i've been making, bit of a test project more than any thing. Thinking i've made an error using 0.5mm alluminum for the enclosure as the sound is gonna travel through it rather than down the horn.
Just have to see how she tests

PS does any one know how to plot SPL's for exp horns, have plotted using a program but i cant find out wht equations it uses. (wanna check responce for my self)

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Old 3rd March 2005, 08:24 PM   #2
mike.e is offline mike.e  New Zealand
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www.cornu.de -similar

You must check out some AES files on FEA modeling of horns etc. I have a PDF on my home pc regarding this,with some amazingly long equations
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Old 4th March 2005, 12:11 AM   #3
Piper is offline Piper  England
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Yeah i know they end up looking huge and some use laplace, i take it there aint any approimations i can use instead ?
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Old 4th March 2005, 12:24 AM   #4
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Looks interesting,

Personally I wouldn't worry to much about the sound traveling through the aluminium. To stop frequencies going through materials, the materials needs to be thick in relation to the wavelenght. That's pretty much impossible to accomplish.

Can you post the simulated response? And what is the compression factor that you used (it seems rather small)?

What program do you use? The SPL plot from Hornresp is known to be pretty accurate.

Mvg Johan
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Old 4th March 2005, 09:11 AM   #5
Piper is offline Piper  England
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Yeah I used the Hornresp program to simulate (yellow line is speakers in free air). The horn is 1.25m long designed for corner use and is purly exponetial.

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Old 4th March 2005, 09:30 AM   #6
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Quote:
Originally posted by Rademakers
Looks interesting,

Personally I wouldn't worry to much about the sound traveling through the aluminium. To stop frequencies going through materials, the materials needs to be thick in relation to the wavelenght.
Mvg Johan

gday!
I'm not sure about aluminium. this looks like copper...
anyway damping factor, logarithmic decrement of metalls is..... not the best

Material E, 109*Pa Material E, 109*Pa
aluminium 70,0-71,0 spider's web 3
beton 14,6-23,2 rubber 0,9
tungsten 415 lead 16,0-17,0
granit 49 steel 200,0-220,0
iron 190,0-210,0 glass 50,0-60,0
kapron 1,4-2,0 cotton 12
brick 2,7-3,0 grey iron 115,0-160,0
ice(about t=-4oC) 10 silk 13
marble 56,0-73,0 wool 6
plexiglass 2,9-4,1 ebonite 3

that's why I use marble
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Old 4th March 2005, 12:16 PM   #7
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Quote:
gday!
I'm not sure about aluminium. this looks like copper...
Yellow!

Hint: Read the first post

Quote:
anyway damping factor, logarithmic decrement of metalls is..... not the best
Not sure what those numbers mean exactly (aluminium 70-71 what?) but marble looks pretty close to aluminium.

As I actually think it isn't really relevant, my main question to you would be: Why do you think it matters and if so in what way?

Since a horn is a pressure/speed transformer, in my opinion it are those 2 factors the aluminium has to basically endure.

The fact that you have a cab made out of marble (nice btw) shows your intended use. But you should not forget there are more intended useable fields out there with other important factors then the ones that matter for your field.

Off course I am curious to find out what the intended use is actually


Mvg Johan
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Old 4th March 2005, 12:40 PM   #8
tiroth is offline tiroth  United States
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Is that flashing? I think resonances could be damped (see: old theatre horns), but does it have sufficient rigidity?
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Old 4th March 2005, 01:24 PM   #9
Piper is offline Piper  England
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Its aluminium mate im sure of it (i built it), im gonna be using this for a sub 40-140Hz. Ill post some pics of wht it looks like now (fully closed up) it aint that pretty but it should do. Ill post my testing resultrs next week but im not sure if the aluminium is gonna flex under big loads, just have to wait and see
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Old 4th March 2005, 01:37 PM   #10
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Quote:
Originally posted by Rademakers

Yellow!

Not sure what those numbers mean exactly (aluminium 70-71 what?) but marble looks pretty close to aluminium.
Mvg Johan
sorry. it's come into view like cooper on the pic.
aluminium 70-71 (E*10^9 Pa)
but you're use very thin alum. therefore:

Quote:
Originally posted by tiroth
Is that flashing? I think resonances could be damped (see: old theatre horns), but does it have sufficient rigidity?
it's shouldn't be rigidity
I made sub, cameras by thick marble for solve damping problem. it's better then lot of inflexibility partitions.
nad that's why I'm afraid your box is not integral, not solid, but it's very importance for sound camera. box must be noiseless
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