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Author Topic: Neumann SM69 and K870 capsule  (Read 1032 times)

RuudNL

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Neumann SM69 and K870 capsule
« on: May 21, 2017, 09:50:59 am »

At the moment I have a Neumann SM69 here for repair.
Looking at the schematic, I see that there is no de-emphasis for the microphone capsule.
But the microphone still sounds good.
As far as I know, the U87 uses the same K870 capsule, but in this microphone a de-emphasis network is used. What could be the reason for this difference?
(By the way: the SM69 is already repaired, the problem was a capacitor.)
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boz6906

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Re: Neumann SM69 and K870 capsule
« Reply #1 on: May 21, 2017, 10:43:14 am »

I've read that the USM69 is basically a double U89 circuit.

But the freq response is very different from the U89.

It does have a 5 dB bump centered at 10 kHz in Omni and Cardioid but it still sounds balanced.
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soapfoot

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Re: Neumann SM69 and K870 capsule
« Reply #2 on: May 21, 2017, 06:41:39 pm »

One thing that comes to mind--

being a stereo microphone, the SM69 will more typically be used at some distance, compared to a U87 or U67, which will very often be placed quite close to a source.

But yes, we have an SM69 FET at our studio, and I haven't ever thought "wow, this mic is a lot brighter than an 87."

I never realized it did not have the built-in de-emphasis network.
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afterlifestudios

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Re: Neumann SM69 and K870 capsule
« Reply #3 on: May 22, 2017, 10:50:02 pm »

I've read that the USM69 is basically a double U89 circuit.

Is this correct?
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RuudNL

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Re: Neumann SM69 and K870 capsule
« Reply #4 on: May 23, 2017, 07:02:29 am »

No, circuit is completely different. (Different capsule too.)
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boz6906

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Re: Neumann SM69 and K870 capsule
« Reply #5 on: May 23, 2017, 10:34:58 am »

Hmmm, Martin is wrong?

"The USM69 is basically a double U89 circuit.

Best regards,
Martin Schneider / Neumann Mic. Development"

http://www.neumann.com/forums/view.php?bn=neumann_mictec&key=1278053612&v=f

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RuudNL

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Re: Neumann SM69 and K870 capsule
« Reply #6 on: May 23, 2017, 03:34:33 pm »

I have the schematics of both of them and I have serviced many SM69 and U89 microphones.
From a viewpoint of construction there is no similarity.
The U89 uses an edge terminated capsule, the SM89 has a capsule with a center screw.
Maybe he means the functionality is the same. (Multipattern etc.)
But that is all I can think of...

By the way: I am talking about an SM69, not an USM69.
But the USM69 also has a capsule with a center screw, the U89 hasn't.
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boz6906

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Re: Neumann SM69 and K870 capsule
« Reply #7 on: May 23, 2017, 04:32:44 pm »

Martin didn't state the capsules were the same, his comment addressed the circuit.


Klaus has said: "You cannot use a U87 capsule in an SM69, fet or tube. The capsule in the SM69 (fet and tube) is interchangeable with the U67/M269 capsule, and bears the same identifier: K67/870"





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David Satz

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Re: Neumann SM69 and K870 capsule
« Reply #8 on: May 24, 2017, 08:48:23 am »

This thread reads as if some people in it are confusing the SM 69fet (with remote pattern switching) with the USM 69 (pattern switches on the mike). They're different animals circuit-wise, though neither model has built-in high-frequency de-emphasis like in the U 67 or 87.

This failure to smooth out the high end has been justified on the basis of the greater typical recording distance as compared to normal studio microphones. But generally if more "presence" is desired in a directional microphone, a response elevation in the midrange/upper midrange would be called for--not a rise an octave higher. Having owned both types of microphone, I found that for many purposes (especially recording in spaces with walls made of hard materials, e.g. stone churches) the SM 69 and USM 69 were simply too bright, even harsh sounding, without some treble reduction in post.
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boz6906

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Re: Neumann SM69 and K870 capsule
« Reply #9 on: May 24, 2017, 11:13:53 am »

It's been my understanding the SM69fet and USM69 are electrically identical, except for remote pattern switching.

"The USM 69 is a 69 fet special version having the pattern's knobs on the mic body, so this mic is not remptely controllable.The mic body is a bit larger."

http://www.neumann.com/forums/view.php?bn=neumann_archive&key=991052248&v=f

IME, the USM hi freq pre-emphasis is useful in most situations  My USM69 is an original 1979 01 version so it may have more low freq response than current units.

Regarding sound propagation in air, losses at 8kHz are about 8x higher relative to 2kHz.

https://en.wikibooks.org/wiki/Engineering_Acoustics/Outdoor_Sound_Propagation
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uwe ret

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Re: Neumann SM69 and K870 capsule
« Reply #10 on: May 24, 2017, 03:29:35 pm »

The SM69fet  and USM69 circuits are very different from each other! The USM69  uses essentially the same circuit (twice) as the U89, albeit a different and larger dual diaphragm capsule.  To the best of my knowledge the circuit used in the SM69fet is unique and not used in any other Neumann microphone.
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boz6906

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Re: Neumann SM69 and K870 capsule
« Reply #11 on: May 25, 2017, 10:55:00 am »

Uwe, thanks for the clarification!

In general terms, what were the changes?

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