Another DIY Ribbon thread

[LineSource]

Alain Engineering (e-speakers.com), know as BEEngineering in Europe, uses a cylinder steel rear surround to complete the magnetic field and provide adequate rear-ribbon volume for extensive sound absorption material to dampen rear ribbon wave reflections.

The two NdFeB block magnets are up front next to the ribbon and form the two pole pieces. Since steel saturates at 1.5-1.7T, using steel next to the ribbon for the pole pieces will create a lower magnetic field than using NdFeB block magnet pole pieces. Large lower strength ceramic magnetics sometimes were put behind large tapered-tip steel pole pieces in order to concentrate the field into the gap at the saturated 1.5T level.

Alain also sells an 3-ribbon MTM design that stacks these cylinder structures. Cost: a few thousand dollars per ribbon.

[tinitus]

Ahh, nice pictures
I have seen those ribbons before, but didnt know it was like that
Its a neat design to use a round thick steel tube

But actually it looks more like a planar tweeter

Looking again it appears like theres two flat leads on diaphragm
One magnet on each side, an one magnet in the middle

Looks quite doable

[tinitus]

My new ribbon magnet system

[brunob]

Originally Posted by tinitus

My new ribbon magnet system

Looks nice.

What is the size of the magnets?

Is there a particular reason to leave a gap between the magnets?




Bruno

[brunob]

I would like to measure the same ribbon tweeter with 9 and 5 microns thick aluminum foil.

Does anyone know where to find 4 to 5 microns foil?



Thanks,

Bruno

[Paul W]

I used 5 micron in my ribbons...believe it originally came from a film/foil cap winding facility. I also remember seeing a company in Germany producing it, but can not remember specifics...it has been too long.

[tinitus]

Originally Posted by brunob

Looks nice.

What is the size of the magnets?

Is there a particular reason to leave a gap between the magnets?

Bruno

thanks
magnets are 1/4 x 1/2 x 1.5"
magnetized through thickness
I got them free from a friend, so the design is random and not that well planned
I consider it experimental proto

I have added a second copper layer (farraday), seperated with cardboard
Seems to give a small improvemnet in strength, and more flattened field shape

[tinitus]

Originally Posted by brunob

Is there a particular reason to leave a gap between the magnets?

Bruno

Good question

Well, if the magnets are forced closer together(ends), it appears to me like the general field gets weaker
I cant prove it tho

It also seems like there could be an optimal minimum/maximum gap size
Meaning that a very narrow field gap has no advantage in field strength

[brunob]

Originally Posted by tinitus

Good question

Well, if the magnets are forced closer together(ends), it appears to me like the general field gets weaker
I cant prove it tho

It also seems like there could be an optimal minimum/maximum gap size
Meaning that a very narrow field gap has no advantage in field strength

I think that is a very good idea! I made some simulations with FEMM. Woaw. I got an increase of the magnetic field from 0.20 to 0.73 tesla!!!!

More details later. I still have to find the optimal gap size.

[a.wayne]

Woah .. are you guys saying there is an advantage in having a gap between the magnets ?

Interesting Hmmm,,,,