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jzagaja 12th December 2008 04:52 PM

Curved magnetostatic speaker
2 Attachment(s)
Anyone have tried curved or even almost cylindrical magnetostatic speaker? Rubber neodymium magnets are made up to N8 grade, price is similar to sintered but grade almost five times weaker. Typical thickness is 2 or 5mm, for multipole pitch is 5mm.

Second thing is how efficient (smooth SPL) is asymmetric motor like this one below.

Ed Holland 12th December 2008 09:22 PM

Apparently yes they have:


I was doing some digging aroung earlier and found the above patent (If the link does'nt work its published as DE3614313 (A1) ). Ultimately I want to try building something similar, I think it has possibilities.


jzagaja 12th December 2008 09:56 PM

Are you able to download more than one page from cited document? It looks like an omnidirectional ribbon horn loaded - clever!

We need to know which motor is better - multipoled or monopoled and what kind of cavities (holes) are optimal. Push-pull seems to be a must for low grade magnets. I'm thinking about long flexible magnet 50mm*1000mm*5mm, N8, 70$, Xiamen China, rest of the membrane passive, ~20cm cylindrical speaker = good WAF.

Ed Holland 12th December 2008 10:21 PM

No, it's one page at a time I think, to stop people scouring their website for everything, and presumably thereby to limit traffic demands.

Back to the invention - yes it is clever. I thought I had something unique in mind until I saw this. I've been doing a few very crude experiments, and the basic concept is promising. My goal was/is to achieve a better high frequency dispersion than speakers like my Magnepans manage. This certainly seems to be achievable, but needs better design to improve the efficiency.

I'm on the verge of ordering Neodymium magnets, and have some ideas about construction that I might share here if I do any more construction work, and there is interest from the forum. Until then it's just speculation on my part :)


jzagaja 12th December 2008 10:33 PM

I can't find foil metallisation just below 1um. Normally it is in nanometer range. From the other side aluminium foil with adhesive is heavy - 30um. First experiments tells me it's better to have controlled path of current flowing in magnetic field. Plain foil with several ohms of impedance was inefficient in my case. Am I right?

Ed Holland 12th December 2008 11:11 PM

Well there are many ways to make this work. One is to make a version of a ribbon source. This requires high current in an intense magnetic field (see some of the threads on full range ribbons for typical magnet structures). Usually, the ribbon is a very low impedance, and employs a step down transformer to match this load to what a typical amplifier can drive.

Then there is the Magnepan approach, with wire bonded to a thin diaphragm. The advantage here was that lots of wire could be distributed over a large area of panel, with wires making multiple circuits through some sections of the field, as necessary.

I have considered both methods.


tiki 13th December 2008 10:56 AM

jzagaja, try this please:
> Recherche
> Einsteiger
> Veröffentlichungtsnummer (DE3614313, split DE)
> Recherche starten
> Anzeige PDF
> press ESC
> 300dpi
> copy the Patent number in the top right, if needed
> Volldokument laden
> fill in the code field (Verifikation Zeichenkette)
> store the document (using the copied number, is desired).
Regards, Timo

jzagaja 13th December 2008 12:52 PM

Thanks a lot Tiki! Anyone talked with Dr.-Ing. Nüsslein Günter about commercial application of his patent? He has Ingenieurbüro in Wedel (Schleswig-Holstein), Telefon: +49 04103/5633.

båndsei 20th December 2008 04:51 PM
Try to look at this Danish site, there is a lot of pictures,but some of the ideas have not been used.The best result was when i taped 10 aluribbon to a planar membrane and fastened it to the frame.My English is not too good, and it is difficult too explain it eveen in my own languege.

jzagaja 20th December 2008 05:25 PM


Excellent, that's a real DIY! I see both long ribbon array and planars on the last page. Tell us few words eg. foil type, conductor thickness, how low it goes, how loud and maybe some measurements?

Ms. Chen from Xiamen is willing to send me rubber neodymium samples in January.

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