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U87 Repair Details
Author: Trahern Jordan
Date: 09/09/2012
Hello,

I would like to send a 1973 U87 in to Neumann USA for repair. However I have a few questions:

1) I would like the current reskinned capsule replaced with an authentic k87 capsule. I had Neumann USA replace one in another U87 I had a year ago and was not happy with the sound. It sounded very 'hard' and quite a large high end frequency lift. How can I ensure that the capsule that is installed in this mic is of the highest quality? Considering the cost I really don't want to be disappointed again.

2) What kind of acoustic tests are done to ensure that the repaired mic performs at the best conditions within the original factory specs? Again, the previous mic that I had worked on sounded completely different than when I sent it in and came back to me sounding very modern, there is nothing 'smooth' or 'warm' about the mic now. If you could detail the tests Neumann USA goes thru to ensure that the mic performs to factory specs I'd appreciate it.

3) If a mic's electronics (caps, fet) have been 'modded', does Neumann USA have the capabilities and parts to return the U87 back to factory specs regarding the electronics? This includes voltage stabilization, the FET transistor and the bias adjustment.

Also, if there's anything you can think of that I should do (what to say, who to contact) I'd appreciate some advice. I want this 1973 U87 to come back good as new and not sounding like a harsh mic that needs lots of eq to make it sound good.

Thank you,
Trahern Jordan  
 
Reply
Re: U87 Repair Details
Author: Uwe Sattler/NeumannUSA
Date: 09/10/2012
1.) All replacement capsules have been 100% tested for their acoustic and electronic parameters at the factory to very tight tolerance. Most often observations of drastic differences between 'before and after' service are due to the deterioration of the 'before' from decades of aging. Contratry to allegations by various outside observers, a capsule manufactured today does match all characteristic specifications of the same capsule model at their time of manufacture. Modern improved manufacturing methods probably allow replacement parts to fall within even tighter tolerance.

2.) Since thorough acoustic testing has been performed on replacement capsules at the point of manufacture with all the sophisticated equipment and test methods used for new microphone production, at the service point verification, tests and measurements are focused on performance of the electronics. The test methods are well established and include verification of gain, frequency response, noise, dynamic range, THD. Any deviation outside the prescribed tolerance bands are corrected, with a detailed description of the findings and remedial services provided.

3.) If 3rd party modifications affect the technical specifications we first consult with the client regarding the reason and/or desirability of the modifications. Yes, we have the capability and parts to restore most Neumann products to factory specifications! However, this is done only when specifically requested and with the express consent of the client.

Any service activity on a microphone starts and concludes with a listening evaluation by our experienced technicians.  
 
Reply
Re: U87 Repair Details
Author: Klaus Heyne
Date: 09/10/2012
Hello Uwe,
You wrote:

" Most often observations of drastic differences between 'before and after' service are due to the deterioration of the 'before' from decades of aging."

Can you be specific as to what type of aging (i.e. performance deviation) may occur in Mylar®-diaphragmed Neumann capsules?
I am not speaking of the obvious deterioration that can come from a capsule's exposure to physical abuse, temperature extremes, etc., but deterioration that has been observed in an unused 10-year-old or older K87/870 capsule. Have you performed measurements in this regard?

Thanks,
KH  
 
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Re: U87 Repair Details
Author: Klaus Heyne
Date: 09/12/2012
see below  
 
Reply
Re: U87 Repair Details
Author: Trahern Jordan
Date: 09/11/2012
Thanks for the response.

My opinion, having the same mic body with 2 interchangeable capsules available (one new and one original), is that the issue I'm referring to when I say the new capsules sound 'hard' isn't related to the frequency response, gain or dynamic range. All these things could co-exist in different capsules and still have different tonalities and timbres.

I'm referring to something that can only be perceived by comparing the two and noticing the 'softness' or 'naturalness' of the original capsule as compared to the new capsule. Whether a Neumann technician can perceive this is solely dependent on if they are aware that the original capsules have this quality and are listening for it when making an observation of the new capsule.

For me, this is what has always made Neumann microphones a (large) cut above the rest; their ability to have a natural and smooth tone that cuts thru mixes and sounds 'just right' when you hear them. The new capsule makes my mic sound like an electronic device that transmits sound thru other electronic devices. The old one sounds like the source more to me.

I'm sorry to say that I really do believe that something has changed in the manufacturing of the k87 capsules over the recent years. I hope that possibly having this discussion inspires Neumann to take a look at the issue and determine whether or not something has changed and, if so, that 'natural-sounding' quality can return to the k87 capsule in the near future.

PS. I would be willing to provide sound files with 2 different vocal tracks, one with the original capsule and one with the new capsule as a way of showing the qualities that I am referring to.  
 
Reply
Re: Details ...
Author: Uwe Sattler/NeumannUSA
Date: 09/11/2012
One accurate measurement is worth a thousand 'expert' opinions!

Since I am apparently not endowed with 'Golden Ears' and a dyed-in-the-wool skeptic of faith based audio comparisons, I have to resort to science based methods of highly refined measurements of the physical properties of audio and its electro-magnetic representation. To the best of my knowledge the defining properties have two measurable dimensions:
- temporal = frequency / phase, and
- scalar = magnitude / amplitude.

If there is any more, I am listening - pun intended - (and expecting a lot of flak)...  
 
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Re: Details ...
Author: Klaus Heyne
Date: 09/12/2012
Uwe,
I for one am not arguing with you about using scientific methodologies for capsule testing. In that spirit, could you please respond to my post?

Thanks,
KH  
 
Reply
Re: Details ...
Author: Trahern Jordan
Date: 09/12/2012
Uwe,

As a way to test the theory you put forth regarding the older capsules sounding different due to age and use, I am trying the following experiment:

I have placed the U87 that Neumann changed the capsule in a year ago (the one that I spoke of earlier that doesn't sound 'right' to my unscientific ears) next to a speaker that is playing a CD of Michael McDonald's greatest hits (big fan, BTW). I have put this CD on repeat and, today, it played for over 10 hours. I will do this for the next 5 days which should give it 60 hours of time to 'break-in'.

I will report back to you on how different it sounds compared to the way it sounded before it was broken-in.

Again, my overall feeling is that you're not taking into account the POSSIBILITY that the tools Neumann technicians use to evaluate the SOUND of a k87 capsule are not the proper tools for determining the audio qualities that I've been referring to (i.e. naturalness). The real tools that listeners of music (the final judges on what sounds 'good') use is their ears. If you're trying to tell me that Neumann technicians value frequency charts and distortion specs in lieu of what SOUNDS good then I really hope that's not the case (but it could explain this particular issue).  
 
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Re: Details ...
Author: Martin Schneider/Neumann
Date: 09/12/2012
We should not begin the measuring vs. listening & feeling debate. It doesn't lead anywhere.

-------------

In my last 20 years of development, measurement & listening tests I've fooled myself often enough to know that I typically need
- a full set of specific, detailed measurements,
- exact description of the recording setup and recording space, or recordings made by myself,
- comparisons, by measurement and listening, where only ONE single parameter was changed at a time, and all other parameters were kept absolutely identical,
- lots of time, to assess results, modify the setup, re-do measurements and listening tests,
- standardized, repeatable techniques
- etc etc.

-------------

Sound files can help to assess defects, but rarely help to tele-diagnose "sound quality". (Whatever "sound quality" may mean, in an instrument like a microphone) See above, "exact description...".

-------------

The concept of "breaking in" a capsule diaphragm is a nice thought, presumably taken from loudspeaker practice. Still, an electrostatic microphone is not an electrodynamic loudspeaker. At 140 dB SPL (full blast trumpet at 4 inches), the diaphragm of your U87 will have an excursion in the 1 micrometer (!) range. A loudspeaker, in comparison, can move by tens of millimeters!
BTW, any means to measure & test your loudspeaker, before & after 60 hours signal?

Best regards,
Martin Schneider / Neumann Mic. Development  
 
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Re: Details ...
Author: Doug Jane
Date: 09/12/2012
Is there any chance of Neumann doing some difference measurements on old and new capsules to show up possible variations due to age? If the measurements are done as differences, by subtracting one curve from the other, then any variations can be magnified. If these tests were done on a representative selection and published, maybe we could move this debate on.  
 
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Re: Details ...
Author: Martin Schneider/Neumann
Date: 09/13/2012
Just in short: done (it's one of the things we're there for, here in development). And, no, no measurements to discuss about.

An old (damaged) capsule might do anything, a new capsule will be up to spec.

Best regards,
Martin Schneider / Neumann Mic. Development  
 
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Re: Details ...
Author: Doug Jane
Date: 09/14/2012
I'm not talking about old damaged capsules, I'm talking about capsules that have been looked after but are old. And it would be usefull for the audio community to get some comparative measurements. Lets say that you find capsules deteriorate severely after 10 years. Don't you think we should know about that? If you are maintaining a Studer tape recorder that is worked hard, then you need to know that the bearings will wear and need replacing. Good studios do regular maintenance.
Microphones fall into this area.  
 
Reply
Re: Details ...
Author: Uwe Sattler/NeumannUSA
Date: 09/12/2012
All I am trying to say is that I trust a well defined and executed measurement more than my (or anyone else's) ears and specific auditory memory.
And no, I have not come across any unused and sufficiently aged capsule with well documented original test protocols to make the suggested comparative measurements. While sober science based experience and knowledge allows me to formulate a likely theory, I refuse to make hasty authorotative sounding dogmatic pronouncements, no matter how plausible. Even if I were able to present incontrovertible hard data, they will likely become the subject of opinionated interpretation.
In spite of my familiarity with Gallileo's fate, and Giodarno Bruno's before him, I would readily convert to new discoveries if they could be consistently repeated and proven with reliable measurements.  
 
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Re: Details ...
Author: Klaus Heyne
Date: 09/12/2012
deleted  
 
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Re: Details ...
Author: Uwe Sattler/NeumannUSA
Date: 09/13/2012
I guess this line of discussion will confirm that scientific based statements could be proved wrong, but pseudoscientific ones can not...  
 
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Re: Details ...
Author: Doug Jane
Date: 09/13/2012
I'm confused! I suggested that you do some meaningfull measurements. I fully agree on the vagaries of the human ear. However it is also a very sensitive instrument, albeit variable.
That is why a Neumann sounds better to it than a Shure SM58.
I am reminded about the story of Geoff Emerick and one of the consoles at Air. He could hear a difference on a couple of channels, but was told they were the same as all others. It was later found that the termination resistors had been left off the transformers in these modules, resulting in frequency response anomalies above 20 kHz.  
 
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Re: Details ...
Author: Uwe Sattler/NeumannUSA
Date: 09/13/2012
Please see Martin's reply from earlier today.
I think we can all agree that the human hearing is a remarkable accomplishment, albeit fairly easily fooled and with imperfect record keeping. That is exactly why we develop and refine methods and measurements to confirm what our senses are subject to perceive.
... and for now I shall get off this soap box ...  
 
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Re: Details ...
Author: Doug Jane
Date: 09/14/2012
OK Uwe, now that we are all agreed about the variability of the ear, how about some facts? I for one would like to know what the expected deterioration rate is on Neumann capsules. And have some information on just how much capsules are affected by such things as being used for vocals over a long period.  
 
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Re: Details ...
Author: Martin Schneider/Neumann
Date: 09/14/2012
The influence of standard use on capsule characteristics: none.

To determine if a capsule is up to original production specs: a selection of very specific measurements, plus skilled inspection and audition. Not for DIY.

Best regards,
Martin Schneider / Neumann Mic. Development  
 
Reply
Re: Details ...
Author: Doug Jane
Date: 09/14/2012
Quote:
The influence of standard use on capsule characteristics: none.

So therefore your previous argument that capsules were old and different is negated. You can't have it both ways!

Quote:
To determine if a capsule is up to original production specs: a selection of very specific measurements, plus skilled inspection and audition. Not for DIY.

This is why I am asking you, the experts, with the right gear, to do the measurements and inform us all.  
 
Reply
Re: Details ...
Author: Trahern Jordan
Date: 09/15/2012
Just to rephrase my original question:

Is it possible that 2 microphone capsules can have different timbres (definied as "the quality of a musical note or sound or tone that distinguishes different types of sound production") while exhibiting the SAME frequency response, distortion, etc?

If so, what scientific objective tools are used to measure these differences and have these tests been performed on the newer batch of k87 capsules versus the older k87 capsules to determine if they are, in fact, of the same timbre?  
 
Reply
Re: Details ...
Author: Martin Schneider/Neumann
Date: 09/16/2012
Hello again,

if we can measure a difference, you might be able to hear a difference (limits given by psychoacoustics). If you hear a difference, we should be able to measure a difference (limits given by the state of the art of measurement technology and knowledge). This is the careful wording of an engineer. But, in any case an acoustical transducer follows the laws of physics, and there is no secret mythology in there.

Standard measurements (freq response, distortion, etc etc) are defined in IEC60268-4. All other measurement techniques are internal, and not for public circulation, as should be understandable.

I have no information that a current K87 should differ from what a K87 sounded (and measured) like in the 1960s - 1980s.

Best regards,
Martin Schneider / Neumann Mic. Development  
 
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Re: Details ...
Author: Martin Schneider/Neumann
Date: 09/16/2012
Re-Quote: The influence of *standard* use on capsule characteristics: none.

There is no routine "ageing characteristic" of capsules. There is no "maximum mileage" of a diaphragm.

And yes, if a capsule is damaged it is "different". And may lack bass, or may lack treble, or may lack sensitivity, or have too much sensitivity and lack bass & treble, or may be susceptible to humidity because of soiling, or may be wobbly because of a fall to the floor, or whatever. And then we recommend an exchange.

Finally, we are not going to inform the whole world on our internal measurement procedures. I guess that might be understandable?

Thank you for this discussion, and have good recordings,

Martin Schneider / Neumann Mic. Development  
 
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Re: Details ...
Author: Trahern Jordan
Date: 09/17/2012
Thank you, Martin, for providing the information you have provided during this discussion.

I now feel confident that, when sending my U87 back to Neumann for repair, that the proper testing procedures will be followed to ensure the mic is put back to factory specs and the capsule will sound how it should.

Sincerely,
Trahern Jordan  
 
Reply
Re: Details ...
Author: Kirk LaBelle
Date: 10/12/2012
Hi Martin,

Thank you very much for your rational scientific approach and patient exposition. I am very glad to hear that there is no routine “ageing characteristic” of capsules. This is good news to me, since I have just purchased a used U87ai that I expect to arrive next week.

I have, however, heard of a different phenomenon that could affect many capsules – not ageing or actual damage, but interference with the membrane’s ability to respond to air pressure fluctuations due to years of accumulation of film deposits and particles from singers’ saliva and airborne matter. These membranes aren’t broken – they’re just dirty.

You folks at Neumann must see thousands and thousands of microphones come to you for repair. You must have some of the best experience with this phenomenon on the planet. So my questions to you are focused on this.

1) Is this phenomenon real?
2) Is it common, after many years of use?
3) In your experience, with regular, conscientious studio use in a non-smoking environment, how long can a microphone go without maintenance and not exhibit any changes to its performance characteristics, due to this phenomenon?
4) How difficult is it to remedy and how would an owner best go about it?

Thanks,
Kirk  
 
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Re: Details ...
Author: Martin Schneider/Neumann
Date: 10/12/2012
Hello Kirk,

- a real sonic degradation is quite difficult to achieve. We recently measured one U89, with tons of deteriorated windshield crumbs on the diaphragm. There, we really missed roughly 2dB in the high end. The diaphragm was literally covered with foam flakes.
- standard condenser microphones work with circuits with extremely high input impedance, including the capsule. Soiling (dust, spit, coffee) is understandably not the best insulator. Keeping this sort of soiling away from the capsule (using pop shields, taking unused mics off the stand and back into the locker,...) can give you decades of uncompromised performance.
Soiling will make itself "heard" via increased, humidity-dependant irregular mic self-noise (rumbling, sputtering, clicks, crackle). If that appears sending in the mic to have the capsule cleaned is the way to go.

Finally, true, we get a certain of microphones to repair per year, but it's not thousands. 1. because the mics don't need that much service, 2. they're often very carefully treated by their users, and 3. we really don't build millions of microphones.

Good recordings!
Martin Schneider / Neumann Mic. Development  
 
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Re: Details ...
Author: Kirk LaBelle
Date: 10/12/2012
Thanks Martin. That's informative. Looking forward to my "newish" Neumann.  
 
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