Ribbon Mic Motor- MRC thoughts

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El Fito

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Hi one and all. It's good to be back. I have been quite busy changing jobs, moving home and what not and, most importantly, devoting a LOT of time and work to coming up with a new "line" of ribbon mics (which I machine in my garage-cum-workshop, heavily laden with industrial tools I got to that effect). Anyway, as I want to come up with the reasonably most efficient, best sounding, niftiest-looking mic I can concoct (don't we all?), I am currently in the process of putting together a test rig featuring a number of motors and a number of trafos, both switchable, to assess what is the best way forward.

The magnets I am using are neos I've had made, measuring 50 mm x 10 mm x 3 mm, with the polarity running across the 10 mm side. I fugured this shape and thickness should make them pretty good for ribbon use.

One of the motors will be a stamped chassis to which will attach the magnets et al., another is a similar arrangement, only that fitted within a mild steel (EN1A silver steel) frame, another will be like the previous one, only that the frame will be iron proper and another one will be the magnets attached to two square (6 mm sq. thick) mild steel rods as above, but without closing an MRC.

Now, here's the question: I will have access to an electric kiln that can bake anything up to 1300 deg C, which I will be using to harden tools and punches and dies. Can I use this to increase the magnetic flux of the steel or iron frame? I have read in previous postings about how it'd be to bake motors at 1200 deg C in a hydrogen fired oven. This one won't be hydrogen fired but, will that make any difference?

As always, any feedback, ideas and points of view most welcome.

El Fito
 

northsiderap

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That temp is perhaps just enough to form a martensite phase in steel if properly quenched.

I've heard that the refined & symmetrical grain structure allows for increased conductance to electromagnetic flux , they do it in transformers.

Supposedly transformer lam steel is 'drawn out' as well to provide an elongation in a particular direction of the steel grain.

I would suppose that the grain direction would indicate the least resistance to flux. Maybe you could try drawing out your pole pieces by machine hammering to enhance a particular grain direction, then quenching from above 1100 degrees to 'freeze' the grain.

Of course you will want to temper & normalize after that.

If you are using structurals such as steel bars, chances are the grain is already oriented lengthwise on the bar.

I'm curious to know if you can hear a real difference between a piece of steel with a specific grain orientation and an untreated/tempered piece of steel in a ribbon motor.

It would interesting to see if attaching your pole magnets at 1100 degrees and THEN quenching would re-orient the grain in any way. I don't suppose you have a powerful electron microscope/microscope huh?
 

Marik

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Try to search the net for pemendur technology. Once I read on this, but am afraid don't remember all the details, as I am not sure if the amount of gain there would justify significant raise of cost.

XVLK might know something on the process...
 

El Fito

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[quote author="northsiderap"] I don't suppose you have a powerful electron microscope/microscope huh?[/quote]

Damn! I knew I shouldn't have melted it to cast those fancy polepieces! :shock:
 

El Fito

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Thanks Marik and Fum. I'll have a look into it.

Since I'll have the kiln lying around (and I'm not planning to start making pottery), I might as well find out as, on the face of it, it would look like a doable procedure (sounds much like hardening steel). Unless it requires something exotic like finishing off with a high power laser beam or subjecting the motor to a meteorite shower or whatever to increase the magnetic field...
 

Marik

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[quote author="fum"]I think Marik meant permendur. :grin:[/quote]

Yeah, pomidor... aaaaaaahhhh, spermadure... I mean...





Screw it..... :evil:
 

CJ

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Sometimes they heat the transformer iron under a mag field to orient stuff.

You might try making the motor frame out of spare I bar lams from an M6 core, if you havesome laying around.

Might be the next big thing, ribbon mic with laminated frame!
 

northsiderap

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[quote author="CJ"]
Might be the next big thing, ribbon mic with laminated frame![/quote]

Ingenious! Who's gonna build it? Marik?
 

Marik

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[quote author="CJ"]He's in Topeka with a bad alternator. :grin:[/quote]

Nah, you confuse everything. The clutch was in Baker, CA, and the alternator in LA. So all this is already fixed, life warranty. :thumb:

What's the next?
Shoot! I might need to check engine mounts. :shock:

Laminations, laminations... need to think about that one for some :idea:.
 

northsiderap

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Here's a preliminary sketch; I'm just trying to follow the flux lines.

RibbonMotor1.jpg


Maybe some D lams with some circles that fit into notches ... (C Core)

The magnets would fit inside of the D-Lams. The top and bottom here could just be replaced by a spacer that separates the two halves of the D-Lams. Probably some tricky spacing in the center if you want to get some nice poles wedged inbetween the D-Lams.

That would make it more pumpkin-shaped.
 
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