[Marik]

With magnets that size you won't get more than 0.3T max.
For 0.8T you will need magnets at least 10mm thick.

Not allways, Tobbie says, that gap/ neodym width is 1:1.
0.8 T may be in  2:1 gap/Neodym, every HDD have it.
 

Oops, my bad. I missed this part. The values I posted are for 1/4" gap.

 

That your 10 mm thick is because you have no magnetic return.

 

The magnetic return does not make too much there. I made experiments with small magnets without return, with return, and simple 1/8" pieces of iron on the other sides of magnets (not looped). In the first case I read 0.23T, second 0.28T, and the last case 0.265T.
With bigger magnets the difference is even less.

The magnetic return does not make too much there.

Maybe, mainly when saturate...
Yes, in tobbie model saturation can occurs, because cross area
of iron is smaller than cross area fo Neodym... But not much.

But why not redirect roles???

Why not make Neodymium rings (like that in Tobbie mic)
and permendur pole pieces ??
Coud it run over 1 T

It could be named Beyer/DESMO  design, after
revolutionary Phillips moving conductor mic, which uses ferrites.

Too much user - manufactured parts, but it could be
interesting experiment, maybe revolutionary from times of Olson,
who had only AlNiCo and had 1.2 dB self noise ?

Hi, all you employed at NASA here, some work for you.

                        xvlk

[Marik]

The magnetic return does not make too much there.

But why not redirect roles???

Why not make Neodymium rings (like that in Tobbie mic)
and permendur pole pieces ??
Coud it run over 1 T

I am not sure about that. First, the price... A few custom made irregular shaped and magnetized Neodymiums :shock:  :shock:  :shock:
The price of permendur pole pieces :shock:

I never played with permendur? What are its losses? What is its saturation? Will the pole pieces need to be big to be out of saturation? Then what about HF response?  

I played with EV-1 mic. What are pole pieces are made of? Iron or permendur???
Anyway, replacing its old weakened Alnicos with the same size Neodymiums did not give any gain in sensitivity. The simple sticking small Neo magnets right to the pole pieces boosted output at least by 6db!

The flux in Coles 4038 drops from 0.6T at the base of pole pieces (attached to the horse-shoe Alnico) to 0.3T at the end (only 1" long). Go figure...

[ToobieSnack]

thanks Marik and xvlk for your wonderful comments and suggestions

WOW xvlk :shock: the ring neo magnet idea and the permendur sounds cool !

i think i have seen on ebay some neo's like you describe .. they may be too small though :?
round wiht a hole in the middle .. not sure of the pole orientation ... probably front to back ... not good right?

on the subject of gap to neo thickness ratio :
i have these 1mm magnets and i am using 4 for a total of 4mm
my gap is actually 5mm so this is a bit off from a 1:1 ration but very close.
i figured with the addtion of the ring MRC and the fact that it is a very efficient MRC
 ..would help to give me a decent flux in my gap.. i hope so ... :? BTW: MRC = magnetic return circuit

i also considered the option of having some tiny pole peices or perhaps stick some of these tiny neo's i have down the center
 (like pole peices ....   it will resemble a T shape but the stem of the T will be much shorter) ..
this is a last resort ...

fito seems to be getting some decent results fron smaller magnet and only one layer ... so ... i thought this would be a good design ..

of course i am only operating on instinct .. :grin: :idea: :grin: lol

later
ts

Go figure...

Here it is:

http://mujweb.cz/www/xvlkxvlk/mic2.gif

(cut and paste link to other browser as usually)

The price of permendur pole pieces

would not be adequate to gain add. You are right at all,
direct using of Neodym is best and cheapest way,
but why not pay 2000 dollars for 3 dB  gain
... or GAIN (without noise)

I intended it only as "variation on the Beyer", i.e. if Beyer
design is good with AlNiCo, what is good with Neodym.

EV-1

my head too smal for that weird numbers.

I never played with permendur? What are its losses? What is its saturation?

maybe 2 T. Don t know, that curve is not straight.

I also not play with it, but some 50 km from me is filial of Carpenter,
that produce this hell. They call it Hiperco.
That playing need Hydrogen owen and 1200 degrees C.
Good for NASA, but today spaceship DIY is common...

         

                                   xvlk

[ToobieSnack]

xvlk EV-1  = electro voice EV-1 ribbon mic ... looks like RCA 74b but not quite as good (most i have seen are all chrome plate)
not as popular as the rca stuff .. you can see some on ebay sometimes ..

at least i think this is what he is talking about ..

later
ts

[Marik]

Go figure...

Here it is:

http://mujweb.cz/www/xvlkxvlk/mic2.gif

Yeah, that's exactly how I envisioned it. By "go figure" I meant losses in pole pieces.

That playing need Hydrogen owen and 1200 degrees C.
Good for NASA, but today spaceship DIY is common...

I read about how to make permendur--time consuming nasty staff.

Yes, EV-1=Electrovoice EV-1. It is very different from RCA-74B, though. Completely different magnetic structure.

[ToobieSnack]

yes ev and rca only similar on the outside ...
i have never seen the inside of a ev-1 ... can you post marik?

That playing need Hydrogen owen and 1200 degrees C.
Good for NASA, but today spaceship DIY is common...

in morganton nc they have a carbon plant and they have oven that will heat to that temperature ..

very dangerous .. i have heard that a small amount of water spilled in these ovens can cause an explosion.. :shock:

ther have been people that have died like this ... :sad:

i don't think i will DIY my permendur :shock: poof :shock: :grin:

later
ts

Ribbon Mic Motor- MRC thoughts

Started by El Fito The Lab

Ideas needed to make a circuit ring - sorta

Started by stickjam Drawing Board

40VRMS Amp to ring old rotary phone

Started by pittsburgh The Lab

Wanted Lexicon MRC service manual

Started by Rob Flinn The Lab