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[klaus]

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

I invite all of you to submit here myths about microphones that you would like to expose in detail 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 is an excellent venue to 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 made the Mic Lab work at full power, let alone transfer important threads in postable form from the old 
   forum. KH May 1, 2011 (+ 7-12-2011.)

[rjc]

That's excellent, Klaus - I'm looking forward to it.

I know it's been covered before, but I hope that one of the myths that will be addressed is the supposed radical difference between the original U87/U87i and the U87 Ai. As owner of both variants I'm well aware that the differences are moderate, in contrast with the way they are frequently characterised.

[radiovinhet]

I've made a comparission between 2 U87Ai stock vs u87i stock.. with same setup. The old version have a little less top end, possible to different gain setup in pre-amps, it needs more 10dB to sound  equal to u87Ai. This is not a myth, this is true;.

[rjc]

The gain difference goes without saying, and is the most obvious difference in spec between the models. Based on my own experience (I own several of each), the FR differences (when the mics are serviced and the capsules are clean) are quite subtle and not consistent with the mythology, which suggests a much more profound difference.

My own experience with these mics is pretty consistent with the discussion about them at http://recordinghacks.com/2011/03/19/neumann-u87ai-vs-u87i/. I'm happy to have both in my locker, and the oft repeated notion that one should be vaunted while the other is all but unusable is pure myth IMO.

[klaus]

The "Recording Hacks"comparison test you cited needs a bit closer scrutiny before you can take its results at face value.
The devil is as usual in the details, obscured by lots of other info. audio clips and background facts thrown around.

For example, a closer read reveals that Mike Pappas contributed his "recently factory serviced" U87i (old version) as test sample. One needs to know that Mike is or was a paid product endorser for Neumann. Nothing wrong with that. But by logical extension of the close relationship, I would not be surprised to find out that the "recent servicing" of his mic by Neumann's factory service center, as mentioned, may also have included a capsule replacement. 
If that was indeed done, then the starkest difference between U87 and U87A would have been obliterated in this test: As I had mentioned in several threads, Neumann's K87/870 capsule has undergone a quite audible change since about the year 2001. (Details too lengthy to repeat here).

If Pappas' mic had a newly installed, current production capsule (the dateline of the the test is early 2011), the starkest difference between old and new U87 would be gone, and the mics truly could sound as identical as claimed, once adjusted for output level differences.

While we are discussing details: Note also that the new U87Ai has a 6.5 dB lower headroom than the old amp was capable off- despite or because of the increased amount of voltage pushed into the FET's gate.

[Bubba--Kron]

How about the myth that tube mics have slower transient response?!?!  That and neve also, both have plenty of transient response.

Cheers

[klaus]

How about the myth that faster transient response is always more desirable in a mic than slower?

[halocline]

How about the myth that faster transient response is always more desirable in a mic than slower?

This is a very interesting point. Classical guitar, for example, is an instrument that many engineers I believe assume should be recorded with microphones that capture fast transients, with the idea that it's more "realistic." (Whatever that means...) I think that guitar sounds best in a recital hall, with a good 30 feet or so of air between the listener and the guitar. This allows the sound to 'bloom' and tends to reduce the finger and string noise. I'm fairly confident most string players would say something similar about violin, cello, etc...

I far prefer the large diaphragm mics I've used for recording classical guitar over the small diaphragm mics I've tried, which include KM84s and schoeps, even though those mics are usually thought superior to the 414s I ended up using. I have this idea that possibly the large diaphragm is a bit slower, which mimics some of the effect of being back further from the instrument; even when both sets of mics are located the same distance from the source, the smaller (quicker?) mics sound "closer" to me, and that's not a flattering effect.

Speaking for myself, I can definitely say that my goal is flattering sound, not realistic! I'm also starting to realize just how psychological this whole issue is. Some recordings of classical music are simply more stressful to listen to, especially over time.

[Jim Williams]

How about the myth that faster transient response is always more desirable in a mic than slower?

Not a myth, just subjective preferences.

[klaus]

Speaking for myself, I can definitely say that my goal is flattering sound, not realistic!

Excellent topic for another mic mythbuster:
realistic vs. flattering
(hint: I think it's a false juxtaposition)

[soapfoot]

There are a lot of things that would be good to see discussed and proved or disproved experimentally and/or experientially; empirically and/or subjectively. 

For example (bear in mind that I am not expressing an opinion on any of the below notions in any way):

1) The impact of coupling cap dielectric and construction style on timbre of passed signal (the notion that "all coupling caps sound the same")

2) The impact of resistor material and construction (carbon film, carbon composition, metal film, metal oxide, thick film, etc) on noise and timbre (the notion that "carbon comp resistors are noisy" or "all metal film resistors sound harsh")

3) The impact of capsule polarization resistor value (the notion that "higher is always better")

[Trahern]

For example, a closer read reveals that Mike Pappas contributed his "recently factory serviced" U87i (old version) as test sample. One needs to know that Mike is or was a paid product endorser for Neumann. Nothing wrong with that. But by logical extension of the close relationship, I would not be surprised to find out that the "recent servicing" of his mic by Neumann's factory service center, as mentioned, may also have included a capsule replacement. 
If that was indeed done, then the starkest difference between U87 and U87A would have been obliterated in this test: As I had mentioned in several threads, Neumann's K87/870 capsule has undergone a quite audible change since about the year 2001. (Details too lengthy to repeat here).

Klaus,
In reference to this above quote, are you trying to infer that, not only has the current K67 capsule for the U87AI changed in recent years (as stated in a previous thread) but the replacement for the K87 capsule for the U87 has changed recently as well?

[klaus]

Yes. Both capsules undergo an identical manufacturing process and are designed along the same acoustic/mechanical construction, including diaphragm tensioning.

Only at the final stage of assembly does one capsule receive a non-conductive spacer between the two capsule halves, along with isolation tubing over the assembly screws (K87), while the other one (K67/870) gets a conductive spacer and naked brass screws.

[Trahern]

So, in essence, the only way to *really* measure the sonic differences between the U87 and U87AI would be to replace both capsules with new ones then compare. Trying to compare a 30 year old capsule in the U87, even if it's been cleaned, and a newer one with a newer capsule in the U87AI is quite unscientific.

[klaus]

It does not necessarily have to be a new capsule for a comparison test of two mic amps, but it should be the same, identical one, transplanted between the two mic amps (using a similar, but not the same, introduces too much of an added variable.)

[Karl Winkler]

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.

 

[klaus]

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)

[radiovinhet]

Hey... anyone tried "Antares Mic Modeler"? 

[soapfoot]

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."

[klaus]

Please elaborate.

[Karl Winkler]

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.

[soapfoot]

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.

[rjc]

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!

[soapfoot]

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

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!)

[soapfoot]

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.

[klaus]

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

[soapfoot]

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

[David Satz]

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

[klaus]

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.

[Kai]

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

[David Satz]

Klaus, I don't feel competent to second-guess what these authors would say if they were here, but in all seriousness, your question is just the one that isn't so easily solved--if the concept of "solved" even applies to it. If we could avoid illusion through an act of the will, we would all be the Buddha, no?

One big source of illusion (or "bias") is that we become attracted to our own theories as to what causes the things that we perceive--but our theorizing and perceiving tend to occur more or less together. In particular the Schulz book deals with this phenomenon--it is (apparently) clinically demonstrable that one's theories can have a great effect on what one does or doesn't perceive within the domain of those theories.

On a modest, personal level I've been studying philosophy of science and particularly the philosophy of knowledge in science for the past year or so. It's been a great and useful shock to discover how oversimpified, ahistorical, and full of wishful thinking the concepts were that I was taught in school. The way I was taught to respect the word of scientists (this was back in the 1950s and 60s) wasn't really very different from the way that medieval scholars were taught to respect the word of religious authorities. On the other hand that's no indictment of science, since science doesn't ask to be "believed in" as such.

There is even quite a bit of science that its own proponents and developers don't claim is necessarily "true" in the absolute sense; they may claim only that the given theory is useful as a basis for ongoing research until the next, better theory comes along. To some people that seems like an appropriate level of modesty while to others, it seems like evasion of a responsibility to establish a narrative.

Apparently when Newton published his theory of universal gravitation, he had no explanation of what gravity was, or how any force could operate across a distance with no physical contact between the objects affected by it. There were critics and dissenters against Newton, some of whom faulted him precisely for that lack of a narrative--even though his equations were accurate enough to describe and predict all the phenomena of time and motion that were observable in his day or for centuries afterward.

--best regards

[Kai]

One big source of illusion (or "bias") is that we become attracted to our own theories as to what causes the things that we perceive--but our theorizing and perceiving .... science doesn't ask to be "believed in" as such. ... the given theory is useful as a basis for ongoing research until the next, better theory comes along.

Be careful not to mix therory and hypothesis.

A theory is a scientific explanation or model of natural effects, sufficiently correct to work within its limits, and it's proven to a certain degree.

A hypothesis is a pure assumption ("believe", "feel", "myth") that needs to be proven, but actually is not.
When proven, the hypothesis becomes a theory.


Example:
Bor's model of atoms (a core with electrons circling around it like the planets around the sun) is still usable to explain most chemical reactions, although it's proven not to be reality.

Now we have fotos of the electrons moving in clouds, which is a strong confirmation that this is the "real" way atoms are built, but still Bor's model (theory) is also used, because it's much easier to handle in some cases.


Regards
Kai

[David Satz]

Hello, Kai. A year ago I would have agreed with you--I would have stood for making a strong, unconditional distinction between a hypothesis (or conjecture) and a theory. But this distinction seems to be observed mainly in the professional discourse of scientists and philosophers. Current American dictionaries don't maintain it for general usage.

When it comes to creating observational bias, any idea that one has about "why X is happening" creates an expectation that "it is X which is occurring"--and this steers one to some extent toward perceiving the occurrence of "X" as we happen to define it, and away from perceiving whatever is inconsistent with "X". That's the opposite of what most people intend when we want to learn the truth about something. But despite our intentions it occurs nonetheless, instantaneously and on a deep level. And we generally don't want to know that about ourselves.

In creating this bias, pure opinion (or hypothesis, or speculation) and the best-founded scientific theory behave in exactly the same way, and that is why I lumped them together. Of course that is not to equate them otherwise, as creationists do when they say that Darwin's theory of evolution is "just a theory" (a statement that relies on ignorance and spreads it further).

I know it's not likely to happen, but I really wish that people would spend five minutes in a bookstore reading the first chapter of either book that I recommended. Amazon sometimes has books set up so that you can read a little of them on line; maybe that's true for these. For folks who are into "audio books" I can recommend The Teaching Company's recorded lectures on "What Scientists Know and How They Know It" (course #1235) as a good general introduction.

--best regards

[klaus]

(...)
When it comes to creating observational bias, any idea that one has about "why X is happening" creates an expectation that "it is X which is occurring"--and this steers one to some extent toward perceiving the occurrence of "X" as we happen to define it, and away from perceiving whatever is inconsistent with "X". That's the opposite of what most people intend when we want to learn the truth about something.

We are lucky in audio to have a method to avoid just that: blind and, even better, double-blind testing.

[halocline]

I believe that the goals in audio are different enough from the goals in most empirical "sciences" (for lack of a better word) to change the nature of evaluation. In audio, the results themselves are judged, over time especially, primarily by perceptions and emotional responses rather than by measurable data. Its more like acoustic instrument building or maybe even wine making.

[David Satz]

> We are lucky in audio to have a method to avoid just that: blind and, even better, double-blind testing.

Those approaches give the most reliable evidence but are costly in time and effort, and can only address a rather limited class of question. I think it's fair to say that most of the opinions that people have about audio aren't directly based on them.

It's not uncommon for the results of various studies of the same question to come up with significantly different results. This implies that the result of a single study shouldn't always be regarded as conclusive, even when that study is carried out in complete good faith. A double-blind test which finds no evidence for a significant audible difference between, say, a tube amplifier based on a triode and another one based on a pentode, wouldn't prove that there is no audible difference between the two amplifiers; another study (even one that used the same two amplifiers) might have a different outcome with different listeners or different listening conditions. And such tests would say little or nothing about triode vs. pentode circuits in general--a more likely subject for a personal opinion.

Even when controlled testing is used, the results are interpreted according to people's pre-existing beliefs such that usually, nothing much is really settled. In the end we still pick and choose our own evidence based on our preferred side of an issue, and tend to distrust any study whose outcome goes against what we believe. That's probably the biggest bias of them all.

[wildcowboys]

Bringing back this topic...

I think one of the most widespread myths is that dynamic mics have a certain "range" close to the capsule and compared to condensers, reject sound originating from beyond this range way stronger than condenser mics - which are said to pick up more room reflections and ambient noise for the same reason.
It simply is not true. When you put up a dynamic and a condenser with similar polar patterns and match output levels using a close source, and then feed them sound from far away, the output levels are still identical. It's just that people tend to keep more instance from condensers, resulting in a more ambient sound.

[Kai]

one ... myths is that dynamic mics have a certain "range" close to the capsule and ... reject sound originating from beyond this range way stronger than condenser mics...

I wouldn't completely name this a myth.

The ambient or distant sound of most low price dynamics (say Shure SM58 to name the most popular) ist quite diffuse and muddy.
There are several reasons for this:

- the transient response or "definition" of a dynamic is bad, smeared.
- The bad transient response is compensated by a strong presence boost, to give the mic more "bite".
- the frequency response is optimized for close distance, compensating the bass boost caused by the close talk effect. From the distance the result is a thin, bass-shy sound.
So in fact bass and lower midrange is "supressed" for distant sounds.
- The polar response is very uneven. Sounds from the side (even at not so big angles) and from the back is extremly coloured, filtered. This is different for every direction, but counts to the muddyness. "Normal" sound is only achieved from the front.
- The output (gain) is much lower (about 10-20dB) then a condenser's. You need more preamp gain for distant sounds. Not all mic pre's do sound good at high gain settings, some are too noisy, some cannot be controlled well at high gain (bad potentiometers).

Dynamics do not "gate" the distant sound - it would be a good tool if such a mic could exist.
But the typical vocal dynamic needs a different handling then a condenser to work well.
Then it can in fact be used to blend out some amount of distant sound on the lower freq. range.

If you turn this round - one can use a condenser quite similar to a dynamic.
Use the lowcut and attenuation on an U87 (+ a bit of EQ), let the vocalist sing with lip contact to the grill and the result will be a high class version of that "stage" sound.
But be advised to use a fine layer of cloth on the grille or you can send the mic to Klaus for cleaning after doing so :-)

Regards
Kai