Ribbon material (a silly question!)

[ToobieSnack]

as for the foil in the caps

i think someone wrote a reply in my ribbon material post (see above) about the voltage of the cap having something to do with determining the thickness..

and... OMG measuring this stuff has got to be near impossible without some specialized instrument.. I used to have some nice lil micrometers ...but I don't remember how small it would measure.. I do remeber measuring human hair...maybe a buddy with a machine shop can help you there...I got my micrometer form a friend who built drag car motors. I wish I still had it....

but i'd like to know this too ....anyone/info?

good luck
ts

 

[maneco]

Thanks for all this information!
My experiments will be really low end,because i don´t think i can source proper magnets here in my country(hey,i can´t source practically a shit here )...i saw somewherean experiment with guitar puckup magnets,i'll give those a try...

Thanks again!

 

[ToobieSnack]

the best source I have found for neo magnets is on ebay...look for:
magneticlife they have a store on ebay and have a wide array of very nice magnets for really cheap.
try that .... if you need help I can buy them for you and send them to you.
trust me... you really need strong magnets...really...you can try older computer hard drives they have neo's in them. the big fat drives.
also be ready to include magnet pole peices , strapping between magnets and a magnetic return circuit with these weaker magnets..it;'s your only chance for high output.
i will have a post soon of my RCA 74b clone and you can see this better. I'll try to get it up by tonight.
marik and other have had great success with neo's and no pole peices (the neo's are the pole peices)...but trust without neo's you will have a challenge...and keep in mind there is such a thing as too much magnetic flux...
i have no idea how much is too much ..maybe someone else can offer this info for us. anyone?
with weaker magnets too much flux will not be a problem...just with the neo's
hope this helps
ts

 

[maneco]

Oh!
i have a bunch of old hard drives,those that look like big 5-1/4 drives!
I did not know they had magnets inside!
Thanks again for your help! I hope to see your clone soon! :thumb:

 

[Marik]

and... OMG measuring this stuff has got to be near impossible without some specialized instrument.. I used to have some nice lil micrometers ...but I don't remember how small it would measure.. I do remeber measuring human hair...maybe a buddy with a machine shop can help you there...I got my micrometer form a friend who built drag car motors. I wish I still had it....

Usually, the thikness is measured by calculating it from foil' weight. You can find online calculator, but the problem is that high precision scales are very expensive. With micrometer you can get only approximate measurement. I have digital with down to 1/2 micron reading and get results all over the place. Nevertherless, you can get at least a thikness "feel" with this.

you really need strong magnets...really...you can try older computer hard drives they have neo's in them. the big fat drives.
also be ready to include magnet pole peices , strapping between magnets and a magnetic return circuit with these weaker magnets..it;'s your only chance for high output.

For use HD magnets look here:

http://www.groupdiy.com/index.php?topic=3444

You don't want "really" strong magnets. Anyway, you won't get a high output. We had a discussion about pole pieces and return circuit, and with Neodymiums they are mostly useless. The target value of magnetic flux is 0.5T, or 5000 Gauss. Go above that and you get LF loss, without any benefits.

 

[Guest]

[quote author="Marik"] The target value of magnetic flux is 0.5T, or 5000 Gauss. Go above that and you get LF loss, without any benefits.[/quote]
What s this???
without benefit? Twice the flux, twice sensitivity.
And with the some ribbon better noise figure.
You can normally go to 1.5 T. For higher values,
you must use very good permalloy to input transformer.
With too low transformer primary inductance you cut bass.
(Because of gyrator, which transforms inductance to compliance)
But higher than 0.8 T induction is hard to obtain with NeodymiumFerrumBoron.

xvlk

 

[ToobieSnack]

thanks marik and xvlt for those target values..
2 slightly different opinions
both of which sound well informed.

xvlt if the neo's can't give that high vlue you stated ...what are you using to get these values?
also have you built a ribbon mic we can see?
what is your source or experience from which you gathered this info.
I ask because I am meeting you for the first time here on the forum.
i am very interested in your additional comments.
please feel free to expand on this for the benifit of newbie's like me.

thanks
ts

 

[Marik]

[quote author="xvlk"][quote author="Marik"] The target value of magnetic flux is 0.5T, or 5000 Gauss. Go above that and you get LF loss, without any benefits.[/quote]
What s this???
without benefit? Twice the flux, twice sensitivity.
[/quote]

Yeah... that's what books say. I tried to increase the field from 4600 Gauss to about 8000 Gauss with not that noticable sensitivity improvement, although theoretically it had to go about 5db up.
The magnet will get much larger and as a result the HF corner go down. (Sorry for typo in my previous message). So to be practtical, the 0.5T value is a nice compromize between sensitivity vs. linear region of magnetic field increase, and size of the magnet, unless you are going to use more esoteric (and much more expensive) magnets.

also have you built a ribbon mic we can see?
what is your source or experience from which you gathered this info.
I ask because I am meeting you for the first time here on the forum.

Toobie,

Make a search on the forum and look at the META and you will find that XVLK is one of the most valuable contributors in ribbon microphones here. He wrote a research paper on the topic. Also, you will find his own built ribbon mic.

 

[Guest]

Hi, Tobi;
Hi, Marik and thanks a much for your credits to me.
Here is some modern design of ribbon mic with
new materials. It is not good for home made, because of two
types of custom Neodym rods. But only as theoretical interest...

http://mujweb.cz/www/xvlkxvlk/modern.gif

(You must cut and paste link to the other browser to see anything...)

xvlk

 

[ToobieSnack]

thanks xvlt

your ring design has been in my head since you mentioned it to me

I think I can do this....I have read about grinding these neo's and i think a machine shop locally can do this for me..

these are neodymium magnets? correct?

I believe I can use some barmagnets and have them grinded to this shape

there is a magnet supplier here that will custom grind/charge my magnets for $60.00 set up charge ...plus the materials ..this price is for a order of 1 or even 25...just add the setup charge to the material cost. :grin: group buy?

question:

would it be possible to :chrome plate: the steel and grind the inner surface so that the steel would still be exposed in the center?

is ther somehting special about this armco steel as opposed to iron?

ALSO:

Can you offer more info on the preamp section? possibly a schematic? :grin:

and again 1000 thanks
ts

 

[Marik]

[quote author="xvlk"]
Here is some modern design of ribbon mic with
new materials. It is not good for home made, because of two
types of custom Neodym rods. But only as theoretical interest...
[/quote]

It is a nice arrangement, with rings somewhat similar to return circuit in Beyer design.
I was modeling this shape of tapered magnets and got significant reduction in magnetic field due to reduced mass of the magnet. I was talking to magnet manufacturer about ordering some custom-made ones of this shape. After some calculations he confirmed my founds. Maybe the magnetic return rings would compensate for this. On the other hand, non tapered magnets with small tapered pole pieces might be a very good option to try. It will concentrate the field, without hassle of going into two differently polarized magnets, and presisely machined rings.

 

[Guest]

[quote author="Marik"]. On the other hand, non tapered magnets with small tapered pole pieces might be a very good option to try. It will concentrate the field, without hassle of going into two differently polarized magnets, and presisely machined rings.[/quote]
No, you can not use pole pieces with neodym if you not
have hydrogen owen and permendur. Yes, I have idea to build
stereo ribbon in one transducer. But that complicated permendur
causes to reject it.

In every hard disc,
there aro no pole pieces, because it is far much costly (that
permendur) than neodym.
I know, that this microphone can not be produced, that is technologically
complicated. But still I mean, that it is only way to make good microphone, without leak flux, small, compact and sensitive, with
cheap materials. Only complication is, that you need custom Neodyms.

Is somewhere on the world, at the university, laboratory of
metalurgy, or some laboratory at the technological institute, where
several unique pieces of Neodym can be made ???
It can not be made at the factory. It is of tooo small quantity.
Neodymium is produced as powder somewhere in Hannau,
it is not so dificult to sintere and magnetize magnet from it.

xvlk

 

[Guest]

[quote author="Marik"]I was modeling this shape of tapered magnets and got significant reduction in magnetic field due to reduced mass of the magnet. [/quote]
Where you was modelling magnetic circuit ???
In the computer? It can be modeled in every 2D modelling soft.
Have you nonlinear models of ARMCO, Neodym etc ????

Thanx a lot,
xvlk

 

[Guest]

[quote author="ToobieSnack"]would it be possible to :chrome plate: the steel and grind the inner surface so that the steel would still be exposed in the center?
[/quote]
You can not pasivate, or chromate ARMCO. it is pure iron and
then there is not corosion.
xvlk

 

[Marik]

[quote author="xvlk"]
Is somewhere on the world, at the university, laboratory of
metalurgy, or some laboratory at the technological institute, where
several unique pieces of Neodym can be made ???
It can not be made at the factory. It is of tooo small quantity.
Neodymium is produced as powder somewhere in Hannau,
it is not so dificult to sintere and magnetize magnet from it.
[/quote]

It is no problem. Right now I am on vacations, travelling in Finland and then in Russia. When I am coming back home I'll check it for you, as the contacts are in my computer.

Where you was modelling magnetic circuit ???
In the computer? It can be modeled in every 2D modelling soft.
Have you nonlinear models of ARMCO, Neodym etc ????

I got a program for Neodymium magnets calculation, but it is in my computer. I have no info on ARMCO.

Yes, I have idea to build
stereo ribbon in one transducer.

Yep, it is a very elegant idea. I remember seeing something for quadraphonic, or Dolby surround arrangement, or something like that. Don't remember details, but IIRC, there were two magnets, lotsa permendur, and four ribbons, arranged in a circle. Need to refresh when getting back home.

 

[Guest]

[quote author="Marik"]Yep, it is a very elegant idea. I remember seeing something for quadraphonic, or Dolby surround arrangement, or something like that. Don't remember details, but IIRC, there were two magnets, lotsa permendur, and four ribbons, arranged in a circle. Need to refresh when getting back home.[/quote]
Why four ribbons???, we are living in the 3D and 3 ribbons in 3 orthogonal
axes are natural continuing in Blumlein 2 axes techniqe.
But it is implssible to made one point 3 D ribbon. But made 2D is possible.


xvlk

 

[ToobieSnack]

OK as for the custom grinding for the neodymiums:

I have researched here locally for this.
I have found a supplier who will custom grind and nickel plate these neo's for $60 set up fee per lot..plus the cost of the individual magnets,,,

they sell a magnet that is 2"x1"x1/2" ....it is magnetized through the thickness (1/2") however this could be magnetized throught the width (1") and then tapered and nickel plated....

I would like to do this and will order magnets for anyone interested.

GROUP BUY????

the magnets are $15 each..... without grinding.
would $15 for magnet and $15 for services be a good price? so a total of $60 for a pair of neo's ....grinded to spec ....and ready to go. sound acceptable? :grin:

Also the reason i ask this is that some forum friends here have asked me to purchase magnets for them and I want to get the best possible solution for them. If I can't work out this custom neo purchase ...I will have no choice but to order the second best solution...a stock magnet....(which is still not bad as many have shown here at the forum...great result with stock neo's) I think, as people who strive for the best possible solutions, it is an obvious and quite alluring path of excellence.
I think if any one of us, alone, were to take on this obstacle it would be a lot of investment...maybe too much to justify the purchase. We could do it together much easier.
Anyone in?

later
ts