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[Tim Campbell]

Dear Klaus,
Glad to see you have your own forum.
I recently hand built a capsule based on a Neumann K67 capsule.
http://www.recording.org/posts1597-195.html
And I'd now like to begin designing my own backplate.
Would you know of any sources for information on this subject?
David Josephson has written a little on the subject of resonant chamber designs. Meaning the relationship between the number and size of holes and size of the resonant chamber in relationship to the surface area of the backplate.

Tim Campbell
Gyraf Audio
EMMA Electronic

[Klaus Heyne]

Man, I just hate this forum's software, just hate it!
I hit just one wrong key, somewhere on the right end of the keyboard, and all my brainstorming I typed out over half an hour is irretrievably gone!

It's never as much fun the second time, but here it goes:

You will not find much in terms of info on condenser capsule design in writing because the capsule is the last great mystery and bargaining chip of a good microphone designer. Therefore, nobody will give away knowledge beyond the trivial.

An example:
I have studied and refined the ELA M / CK12 capsules ( I own the ELA M trademark)
This capsule's most attractive sounding generation (there have been many) has certain design features not shared by other, seemingly identical CK12s.

If I were to reveal what I found out, my competitive edge, at least in that field, would be gone.
I wish it was different. I wish, designers could work together to share knowledge and pool their combined brain power.  The result would be so cool- there would be many more outstanding capsule designs than currently exist, and not so many useless clone duds masquerading as "like original", confusing and frustrating the buying public.

I can only refer you to two resources readily available:

1. Neumann's excellent (but very dense) booklet "Microphones" , by Gerhart Bor

[Tim Campbell]

Dear Klaus,
Thanks for your reply.I've also frustratingly erased replies before I got a chance to post them.

I understand about not revealing aspects of your own work. That was also my interest in backplate design. I have no desire to infringe on Neumann or AKG's capsules.

I guess there's no substitute for hard work.

Good luck with your forum.

[David Bock]

The AIP Handbook of Condenser Microphones has some of the formulas for holes and slots for backplate damping, but it only deals with pressure mics and you'll have to be really good with math.
regards,
David Bock

[Fletcher]

Klaus Heyne wrote on Sun, 25 April 2004 18:07

If I were to reveal what I found out, my competitive edge, at least in that field, would be gone.

If I'm not mistaken, this is exactly the reason why there is a patent office... so your work can be protected, while it helps others advance the science...

[David Bock]

Not exactly, sometimes it just provides a roadmap for immitation w/o infingement. I know that my father in law had some pharmecutical products he invented and opted NOT to patent, so the big companies wouldn't reverse engineer using the patent (when he felt theyu could), and some things he was able to licence the rights to the patent (when he felt they couldn't reverse engineer). I figure the same reasoning went on when Neumann DIDN'T patent the KK67 capsule.
regards,
David Bock

[Jakob Erland]

I talked to an engineer from our local DPA (former Bruel&Kjaer), and he told me that the reason why they do rarely patent anything is exactly that: The patents simply makes it too easy to copy the product.

Microphone patents are often obscured by not using company names, just inventor's names.

Here are a couple of the "interesting" patents that I have managed to find:

(Referred to as: "Kalusche Spardock 1951"): (Actually: KALUSCHE DIPL-ING HEINRICH;; MUELLER DIPL-ING HEINZ;; SPANDOECK DR-ING FRIEDRICH, 1948)

Main German patent 836 955 C1:

 http://l2.espacenet.com/espacenet/bnsviewer?CY=gb&LG=en& amp; amp;DB=EPD&PN=DE836955&ID=DE++++836955C1+I+

German patent 821 217 C1:

 http://l2.espacenet.com/espacenet/bnsviewer?CY=gb&LG=en& amp; amp;DB=EPD&PN=DE821217&ID=DE++++821217C1+I+

German patent 828 707 C1:

 http://l2.espacenet.com/espacenet/bnsviewer?CY=gb&LG=en& amp; amp;DB=EPD&PN=DE828707&ID=DE++++828707C1+I+

Maybe also..
German patent 808 593 C1:
 http://l2.espacenet.com/espacenet/bnsviewer?CY=gb&LG=en& amp; amp;DB=EPD&PN=DE808593&ID=DE++++808593C1+I+

M7 capsule, old version?:

(Referred to as: braunmuhl weber 1927)

(Actually: WEBER WALTER DR (DE); BRAUNMUEHL HANS JOACHIM VON DR (DE))

 http://l2.espacenet.com/espacenet/bnsviewer?CY=gb&LG=en& amp; amp;DB=EPD&PN=GB472549&ID=GB++++472549A++I+

..These patents are very well hidden - took me weeks looking through the patent servers to find these. Seems like they don't like you to find them too easy..?

Jakob Erland
Gyraf Audio

[Oliver Archut]

Every year there about 25ooo! microphone patents are applied for, mostly for cell phones, etc. last year there were about 20 US patents for studio microphones, and most of them are just variations on existing stuff to make the shareholders happy to invest into a company that has a patent.

By patent law every company is required to disclose their protected good with the issued patent number on the item. Also you can inquire at any company about their patents and in most cases they will send you a copy of their patent letter, or have to tell you their patents numbers by law.

You can go into your local patent office (at least here in the US) and get a copy of every patent that was issued about let say condenser mics, for free I might add.

But even than there is not to much stuff going on in the condenser region, the basic design is still the same for about 90 years, the M7 was an patent undermining version of Mr. Wentes design. The 251 was designed to undermine Mr. Grosskopfs design, etc. How about something new?

Best regards,

Oliver

[Jakob Erland]

Patent database searches for both Mr. Wente and Mr. Grosskopf comes up with no microphone-related patents at all. But surprisingly many farming tool patents..?

Do you have more specific information about these patents?

Jakob E.

[Trazan]

Jacob, as you're Danish, you would most probably understand written Norwegian. Have you heard, or know anything about this microphone design?

http://www.nrk.no/programmer/tv/schrodingers_katt/3429013.ht ml

There's not much information there, but if it sounds good it looks interesting.

Rune "trazan" Thoen

[Jakob Erland]

The links from that page to the video media files dosen't seem to work..

Judging from the looks of it alone, it could be an "intelligent directivity" type microphone, used to track and pick up specific signals like human voices. Very interesting for e.g. conference recording and video-phones. I know our local B&O is working with something like that. But the sound quality? - I doubt it..


Jakob E.

[Buzz]

you guys can search at www.uspto.gov for us patents , there are very detailed searches available ( IE search for large diaphram in the patents )

LAter
Buzz

[Klaus Heyne]

Yo, Mr. Buzz:
Unless you use your real name from here on (see Ground Rules), there won't be any more buzzing around this forum by you. Deal?

[Jakob Erland]

Found the GrossKopf patent:

http://patimg2.uspto.gov/.piw?Docid=02787671&homeurl=htt p%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect2%3DP TO1%2526Sect2%3DHITOFF%2526p%3D1%2526u%3D%25252Fnetahtml%252 52Fsearch-bool.html%2526r%3D1%2526f%3DG%2526l%3D50%2526d%3DP ALL%2526S1%3D2787671.WKU.%2526OS%3DPN%2F2787671%2526RS%3DPN% 2F2787671&PageNum=&Rtype=&SectionNum=&idkey= D2EC12B44970

..quite a link, eh?

Jakob E.

[Oliver Archut]

I checked the archives online but the Wente patents you only can look up in the hard paper patent archives. But here is what I found in my archive on the AEG-Telefunken spin on the Wente design made in 1928 and is called the CMV1.

check it out http://www.tab-funkenwerk.com/cmv1.html

Circuit is identical to the CMV3 same tube, etc, and I know there was the CMV2 in the familiar Neumann bottle shape, but no pic....

Regards,

Oliver