Diy AMT

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#521
solhaga said:
That is my experience as well. While it might do wonders (gaining 5-6 dB due to the mouth's dimensions) in the low frequency region, it really screws up the response in the high frequency region, that is corresponding to the throat's dimension and curve. A carefully simulated throat is a must along of course with a really smooth design and making.
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A horn does not have to be the source of high frequency problems.

There are methods that can be used to make the horn work in higher frequencies. You simply have to divide the throat with a few vertical pieces that are spaced apart in the wavelength that you want the horn to work up to. As an example the wavelength of 10 kilohertz is approximately 25mm. SO any area that is wider will have the ability for the reproduced sound to bounce over this path and cause a partial loss in the output.
 
#522
Or as båndsei is doing; having a flatter throat and thus avoiding parallel walls.
Problem remains with the parallel walls in the magnet gap itself though, but there's a
232634-yet-another-diy-amt-20.html
.
 
#523
Sorry, should have been a link:

solhaga said:
Or as båndsei is doing; having a flatter throat and thus avoiding parallel walls.
Problem remains with the parallel walls in the magnet gap itself though, but there's a http://www.diyaudio.com/forums/planars-exotics/232634-yet-another-diy-amt-20.html#post4550803.
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Problem with vertical bars to get several adjacent throats, is that it will be more mechanics that can vibrate when excited by low end of the spectra.
Couldn't there be some comb effects as well?

I've tried reticulated foam used for HVAC but with no effect.

(Båndsei, your turn to get some popcorn)
 
#524
Trouble with shallow horn flare is that not much will happen for all the work of making a horn.

With balance in the design and making of the horn there are enough benefits to make it worth while.

But it is not a simple thing to do to the best possible effect.

Reticulated foam is only useful under limited circumstances. I know that it was used by Earl Geddes as a bandaid for some of his troubles with horn design.

But it was an intelligent application of a product in the right place. It is not something that works in many other situations.
 
#526
båndsei said:
Drinking bear and building carporthttps://s-media-cache-ak0.pinimg.com/originals/4c/f3/81/4cf381dac1b8230999fa4f0a80445c8c.gif
how much helps a baffel at 500 Hz.https://s-media-cache-ak0.pinimg.com/originals/4c/f3/81/4cf381dac1b8230999fa4f0a80445c8c.gif

Bernt
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well i have a tiny one now that plays from 600 and a baffle does nothing in my measurement. thats weird, will try to measure again a bit further away. i think i screwed it up by measuring at 40 cm 🙂. gone get me some beers to 🙂
 
#528
mwmkravchenko said:
Trouble with shallow horn flare is that not much will happen for all the work of making a horn.

With balance in the design and making of the horn there are enough benefits to make it worth while.

But it is not a simple thing to do to the best possible effect.

Reticulated foam is only useful under limited circumstances. I know that it was used by Earl Geddes as a bandaid for some of his troubles with horn design.

But it was an intelligent application of a product in the right place. It is not something that works in many other situations.
Click to expand...
Thanks for the clarification. It concurs with my view of wave-guides.
In fact, perhaps just a simple baffle as båndsei suggest is enough to gain a couple of dB in the low end.
I have't found any impact from the use of the reticulated foam, yet.
 
#535
Just ask. It is amazing what happens when we ask the right questions to the right people.

Even the source for the metalized film for capacitors.

If a contact can be made there you can get further down the supply chain and find someone that is willing to sell smaller amounts.

in 1996 I was asked by one client to develop copper foil inductors. I was able to get a contact with the mill that made the copper foil. And all that came at a price that no one would sell the product to me for until I had the right contact.

Don't ask.

Don't get.
 
#537
båndsei said:
BREAKING NEWS !!!!

Soft AMT
res_freq_soft_amt_w_paper.JPG
[/url][/IMG]

Diaphragm 32x80x10mm.
Made from PVDC film and alu with paper, and spray glue
Have not measured freq responce yet.
Beat this :Res freq. 130 Hz.

Bernt
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oh wow... no i am insanly curious to the feq response!!!! 🙂 !!!! i can imagine it is pretty heavay spray glue with PVDC so im very very curious about the high end of the thing 🙂 very small panel for such low res 🙂
 
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