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Author Topic: Microphone Myth Busters: Overview  (Read 19265 times)

Karl Winkler

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Re: Microphone Myth Busters
« Reply #15 on: May 18, 2011, 03:37:38 PM »

As soon as the transfer of relevant threads (including my sticky forum) has taken place*, I will be posting in a new series of threads with the above title.

I invite all of you to submit myths about microphones that you would like to expose to daylight. The kind of lore that keeps perpetuating on internet forums without anyone putting an authoritative stop to it, once and for all:
tube mics sound warm; copy capsules sound like originals; 'neutral' vs. 'colored' mics, etc.

As many of these myths are self-serving to those who spread them, this forum whose ground rules and moderator discourage commercial infiltration can shine a light on them. So share generously and boldly!


* This was written... how many weeks ago?
   The company which runs this forum still has not seen fit to make the Mic Lab work at full 
   power, let alone transferring important threads from the old forum. KH May 1, 2011.

Here's a few:

Old mics always sound better.

Tube mics always sound better than solid-state mics.

Mics with transformers at the output always sound better than transformerless versions.

Consecutive serial numbered microphones are intrinsically a "matched pair".

Directional mics don't have the bottom end response of omnis ("just look at the graph on the data sheet!")

Mics made in a particular country are always better/worse than some other country.

Condenser mics can't be used on stage.

Large diaphragm mics can't be used for miking kick drums because they will be damaged. (really old mics with PVC diaphragms excepted...)

Microphones can be accurately modeled using DSP.

 
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In theory, theory and practice should be the same. In practice, they are not.

klaus

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Re: Microphone Myth Busters
« Reply #16 on: May 18, 2011, 03:50:50 PM »

Almost all of them super ideas! (I like the last one the best)

Now if only the management would get its act together, and start me a forum I can use, so I can start delving into these hot-button issues!!

Thanks, Karl, and I hope you are well! (Karl was for many years the go-to guy at Neumann-USA)
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

radiovinhet

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Re: Microphone Myth Busters
« Reply #17 on: May 18, 2011, 05:08:08 PM »

Hey... anyone tried "Antares Mic Modeler"?  :D :D :D :D
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soapfoot

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Re: Microphone Myth Busters
« Reply #18 on: May 20, 2011, 12:50:19 AM »

Here's one I heard the other day, and hear from time to time: "The U48 is the same as the U47, except that its two patterns are cardioid and bidirectional instead of cardioid and omni."


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klaus

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Re: Microphone Myth Busters
« Reply #19 on: May 20, 2011, 01:00:27 AM »

Please elaborate.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Karl Winkler

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Re: Microphone Myth Busters
« Reply #20 on: May 20, 2011, 09:54:08 AM »

Here's one I heard the other day, and hear from time to time: "The U48 is the same as the U47, except that its two patterns are cardioid and bidirectional instead of cardioid and omni."

How is that a myth?

http://www.neumann.com/?lang=en&id=hist_microphones&cid=u48_publications

Some very slight circuit differences, from what I remember, but otherwise that's pretty much the truth.
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In theory, theory and practice should be the same. In practice, they are not.

soapfoot

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Re: Microphone Myth Busters
« Reply #21 on: May 20, 2011, 10:29:45 AM »

My mistake.  Upon studying schematics for both mics awhile back, I misread the capsule polarization voltages.  I had been operating under the (false) impression that the 47 had a higher polarization voltage than the 48, when re-examining the schematics today, I realized that I had mistaken a "53" for a "63" on the U47 schematic.  My apologies.
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rjc

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Re: Microphone Myth Busters
« Reply #22 on: May 20, 2011, 11:20:46 AM »

My mistake.  Upon studying schematics for both mics awhile back, I misread the capsule polarization voltages.  I had been operating under the (false) impression that the 47 had a higher polarization voltage than the 48, when re-examining the schematics today, I realized that I had mistaken a "53" for a "63" on the U47 schematic.  My apologies.
Well, appropriately, that's another myth that's now been busted. ...Though not in the direction you were expecting! :D
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Ray Cologon
Darksky Media
http://www.darksky.com.au

soapfoot

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Re: Microphone Myth Busters
« Reply #23 on: May 20, 2011, 11:55:20 AM »

Well, appropriately, that's another myth that's now been busted. ...Though not in the direction you were expecting! :D

:D

I'm all about the learning, even if it means I end up looking less-than-smart (which is actually a fairly common occurrence for me around here!)
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soapfoot

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Re: Microphone Myth Busters
« Reply #24 on: May 20, 2011, 01:47:32 PM »

I was doing some searching about this, and I ran across this older thread, which would seem to be in line with what I originally thought.  Perhaps Klaus or anyone else can set me right on this once and for all.  In fact, I remember reading this thread when I was doing a lot of reading through the archives of the old forum.  Maybe this is what put the thought in my head.

http://recforums.prosoundweb.com/index.php/m/435703/21957/?srch=polarization#msg_435703

Particularly message 435703.
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klaus

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Re: Microphone Myth Busters
« Reply #25 on: May 20, 2011, 05:14:14 PM »

Martin is correct in his post. Others and I mentioned the same in various posts over the years:

The polarisation voltage in cardioid differs up to a whopping 10.5 Volts! (20%!*) between the two mics. This deteriorates the noise floor of the U48, as well as the dynamic behavior of both mics. (The Beatles with their audiophile-quality recordings of the late 1960s did not seem to mind, though.)

If  something less than a full figure eight as secondary pattern is acceptabel to the user of a U48, the voltage divider on the mic amp board can be changed to then yield the same polarisation voltage (and sound!) as a U47.





* for mysterious reasons, some of Neumann's schematics show a 60VDC polarisation voltage for U47, others 63VDC- with the same exact circuit and supply voltage of 105VDC
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

soapfoot

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Re: Microphone Myth Busters
« Reply #26 on: May 20, 2011, 05:16:04 PM »

Thanks, Klaus.  Good to know I'm not (entirely) crazy. 
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David Satz

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Re: Microphone Myth Busters
« Reply #27 on: July 04, 2011, 12:09:02 AM »

Rather than say anything particular about microphones (although I may do so later, since I'm convinced that one "myth-busting" claim made earlier in this thread is itself based on myth), I'd like to recommend two books that I've read recently: The Invisible Gorilla by Christopher Chabris and Daniel Simons, published by Crown (Random House), and Being Wrong by Kathryn Schulz, published by ecco (Harper Collins).

Both books focus on a human problem that has obvious relevance to audio: We all have a certain level of confidence in our beliefs and perceptions (whatever level of confidence we may happen to have), but this degree of confidence may have rather little to do with how reliable those beliefs and perceptions actually are--and we aren't necessarily in a position to know how wide that gap may be in any given instance.

Both books are well written, well documented, and (particularly the Schulz book) fun to read. And each book has jaw-dropping examples from real life that are worth knowing about, even apart from the author's thesis.

--best regards
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klaus

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Re: Microphone Myth Busters
« Reply #28 on: July 04, 2011, 02:36:52 AM »

So what would be the authors' solution to the dilemma of self deception, especially in the world of audio, where so relatively little is scientifically provable?

In these instances  when listening was the only way to ascertain a certain property (cables, capacitors) I always have relied on repeat testing- different days, different moods, states of tiredness, etc. When my opinion stays clear and constant through different listening cycles, and in well-controlled testing arrangements (at least single blind) I tend to rely on it eventually, and feel comfortable to share it with others.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Kai

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Re: Microphone Myth Busters
« Reply #29 on: July 04, 2011, 10:10:07 AM »

Directional mics don't have the bottom end response of omnis ("just look at the graph on the data sheet!")
There is an explanation for this true statement: directional and omni mics are seeing different types of soundwaves.

- An omni is seeing air pressure changes. Pressure changes do not have a direction.

- A directional mic (the only pure one is fig. of eight) is seeing air movement into a certain direction (the mic axis), while ignoring others (perpendicular to axis).

If you look at a sound wave, it's a combination of both, but the max value of each part is on different places of the wave.
When the pressure is max, the movement is min.
The max values of pressure and movement are 90° (quarter wavelength) apart.
This is most audible where wavelengths are large, say frequency is low, e.g. 1.7m for a 50Hz wave.

Next difference is:
Air pressure is not getting bigger for lower frequencies.
An omni is a diaphragm mounted over a closed cavity.
Threrefore nothing limits its low frequency movement, as diaphragm movement is always proportional to the air pressure.
It can, if built for special purposes, have an LF response down to 0,01Hz or below, only limited by the electronics used.


Low freq. have bigger air movements than high frequncies.
The ideal fig. of eight is a diaphragm quite losely tensioned, hanging in the air like a curtain.
But - stop - a condenser mic's diaphragm can't be tensioned too loosely, it has to stay in place when polarisation voltage (e.g. 60V) is applied (static voltage pulls the diaphragm against the plate).
And the pol. voltage even enhances the tension by pulling.

If the diaphragm has a certain tension, it cannot follow air movement freely.
So LF response is limited.

In theory a ribbon would be the solution, but it is not - the ribbon mass is too high to follow low freq.'s air movements, the air is simply passing by the ribbon instead of moving it.

These are the reasons for both types of mics sounding completely different in the LF range.

BTW: Cardioid is a combination of both types, omni + fig. of eight, with some frequency crossover points as I described here:
http://repforums.prosoundweb.com/index.php/topic,1198.msg6272.html#msg6272


Regards
Kai
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