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Old 14th June 2011, 01:02 PM   #21
bentl is offline bentl  Norway
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Hi, what is the widt of the ribbon, and the size of your magnets?

Interesting build!

Regards
bent
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Old 14th June 2011, 02:58 PM   #22
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Quote:
Originally Posted by bentl View Post
Hi, what is the widt of the ribbon, and the size of your magnets?

Interesting build!

Regards
bent
The ribbon in my first post is 27mm wide and 1050mm long. Magnets are N35 10*10*150mm.
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Old 14th June 2011, 03:59 PM   #23
UKPD is offline UKPD  United Kingdom
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Originally Posted by ABJensen View Post
I use capacitor paper from a now closed capacitor factory.
No problem too corrugate when sandwiched with paper.
It is very strong ribbon. the planar ribbon in the youtube clip
is crossovered at 200hz. Ok very step digital filter.The 1meter
true ribbon is crossed at 1000hz 12db
Thanks ABJensen,

I'm trying to find source of that fine Washi paper, should'nt be far off the thickness of the capacitor paper, I think. Otherwise I've got few meters left of DuPont Mylar 3um, but that will not corrugate well.
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Old 14th June 2011, 04:03 PM   #24
brunob is offline brunob  Germany
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Quote:
Originally Posted by ABJensen View Post
This ribbon is made of 0.6my aluminium and 12my paper back.
The ribbon is 27 mm wide and 1050 mm long. This gives 2,2 0hm,
so no need for transformer or resistor.
Would a 6 microns aluminium ribbon with a 2 ohms resistor in series be equivalent? The 12 microns thick paper is probably lighter (factor 1.35 estimated) than 6 microns aluminium ribbon.
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Old 14th June 2011, 04:14 PM   #25
brunob is offline brunob  Germany
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Quote:
Originally Posted by ABJensen View Post
The ribbon in my first post is 27mm wide and 1050mm long. Magnets are N35 10*10*150mm.
With such a wide gap (27 mm) and small magnets with a square section (10x10 mm), the magnetic field is very uneven in the ribbon gap - weak in the middle compared to the magnet surface. But then, if it sounds good ...
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Old 14th June 2011, 06:22 PM   #26
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by brunob View Post
With such a wide gap (27 mm) and small magnets with a square section (10x10 mm), the magnetic field is very uneven in the ribbon gap - weak in the middle compared to the magnet surface. But then, if it sounds good ...
Brunob , could you explain your position on this a bit more , the middle will always be weaker than the ends, are you suggesting a different magnet size (instead of 10x10 ) to give more field strength in the middle ..


regards,
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Old 14th June 2011, 07:32 PM   #27
UKPD is offline UKPD  United Kingdom
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Quote:
Originally Posted by brunob View Post
With such a wide gap (27 mm) and small magnets with a square section (10x10 mm), the magnetic field is very uneven in the ribbon gap - weak in the middle compared to the magnet surface. But then, if it sounds good ...
What about adding helper magnets in the middle, instead of steel pieces to close the magnetic circuit. You could space them out to
compensate for weaker field in the middle and no problems with saturation point of steel. Also use stacked disc or rod magnets to
minimise reflections from the back.

Peter.

Last edited by UKPD; 14th June 2011 at 07:38 PM. Reason: addition
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Old 14th June 2011, 07:53 PM   #28
bentl is offline bentl  Norway
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What software are you using to measure?

This build is very similar to my ribbon prototype that I built a few weeks ago.

I will redo the ribbon with supports spaced along the ribbon as it tends to move out of the magnetic field. Also I will build a more "domestic" construction in a wife-acceptable design and colour when the time comes.

regards,

Bent
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Old 15th June 2011, 06:36 AM   #29
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I havent measuret them yet. But will use the software for my DSN28 pre Ground Sound . And Holm freeware.

And yes mine is very smilar, they will probably almost measure identical.

I will probably have too put some spacers one mine too. This super thin aluminium gives very little spring effect.

Last edited by ABJensen; 15th June 2011 at 06:39 AM.
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Old 16th June 2011, 06:55 AM   #30
brunob is offline brunob  Germany
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Quote:
Originally Posted by a.wayne View Post
Brunob , could you explain your position on this a bit more , the middle will always be weaker than the ends, are you suggesting a different magnet size (instead of 10x10 ) to give more field strength in the middle ..


regards,
I performed several FEMM simulations and measurements. Narrower magnets and deeper cavities give a more homogenous magnetic field in the gap.
See "The tall neodymium ribbon". Part 1. See also DIY ribbon info requested (constructing a ribbon unit)
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