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Author Topic: "Breaking In" Mics?  (Read 11839 times)

Haolemon

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"Breaking In" Mics?
« on: July 13, 2014, 12:29:53 pm »

As a musician, I note that one has to "break in", via use, certain items, such as guitar strings, acoustic guitars, amplifier speakers, drum heads, etc.  Does this apply to microphone diaphragms?  Since they are under tension, does some use and the vibration involved cause them to change from their new condition?

I haven't seen this discussed before, perhaps because the question is unworthy :)

Thanks
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Kai

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Re: "Breaking In" Mics?
« Reply #1 on: July 13, 2014, 01:53:39 pm »

For musical instruments what you call "break in" is undoubtly very important.

A high quality condenser mic - on the other hand - is constructed with the goal that it should NOT change its sound over time.
For this purpose, some critical parts of it are even pre-aged.
So once it's delivered, its sound should stay the same for a long time.
Breaking in with sound of any kind (except explosions) for sure wouldn't change the mic.
Only environmental circumstances like very high temperature or excessive humidity or a combination of both can "break" - not "break in" - a mic.
I say "break" because every change is unintentional here.

Some electronic parts, specially electrolytic capacitors, can change a bit if in use after a long time with no power applied to them.
This is called "reformatting", because they where already "formated" in the factory.
The effect is very little and mostly inaudible, as those C's are usually not in the audio chain.
Plus - it's only necessary to put power on them to do this, no special signal required.

Regards
Kai
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polypals

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Re: "Breaking In" Mics?
« Reply #2 on: September 04, 2014, 05:14:42 pm »

Maybe it is not the intention of the maker but condensor mikes do deteriorate after prolonged use in high SPL environment. The capsules get tired and will not perform like they are meant to.
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Kai

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Re: "Breaking In" Mics?
« Reply #3 on: September 05, 2014, 08:09:12 am »

It's not so much high SPL that makes, e.g. gold flake off the diaphragm, but humidity, dirt, and saliva spray from singers, or simple aging.

The now "historic" mics weren't constructed to last for 40 or 60+ years. So don't blame them if they don't.

High SPL is relative, BTW:
One extreme: you can break a mic if you put it into a bass drum, where not only SPL is beyond 140dB, but even air is "blown" out of the skin hole.
In this position it might be worth to use a popshield or foam cover to protect the mic.

Another way to break a mic are stage pyros exploding close to the mic.
I know of one case where an overloaded (DIY) pyro's explosion killed all mics nearby, thankfully none of the musicans were seriously injured.

So a mic isn't unbreakable by SPL, but if your ear can stand it the mic is not in danger.

Regards
Kai
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polypals

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Re: "Breaking In" Mics?
« Reply #4 on: September 05, 2014, 04:09:03 pm »

Bass drum is a good example, it will destroy an excellent U67 or the later U87 in a couple of months studio use.
High SPL? Sure used this way the output of the mike reaches line level.

No commercial studio can afford to record a drum kit rigged up with 40.000 $  worth of Neumanns.
Enough dynamic alternatives that will do the job just as well saving the Neumanns for the purpose they are meant for.
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Kai

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Re: "Breaking In" Mics?
« Reply #5 on: September 07, 2014, 07:40:38 am »

Bass drum is a good example, it will destroy an excellent U67 or the later U87 in a couple of months studio use.
I don't know of any case where a U67 or U87 broke by use at or inside a bassdrum, mainly because I've never seen someone using these mic's for that purpose.
U87 distorts in the range of about 120+ dB, so on a bassdrum played with normal level it doesn't make much sense.
U47 FET (not U47 tube version) is used here quite often in front of (not inside) kickdrum with good results and no problems.

No commercial studio can afford to record a drum kit rigged up with 40.000 $  worth of Neumanns.
Enough dynamic alternatives that will do the job...
There are condenser mic's that can be used with drums, giving excellent results, far more open and transparent then any dynamic.
I, e.g., do use AKG C451 with -10 or -20 dB pads on drums, never ever any of those broke.
I make my decision to use condenser or dynamics based on the sound I'm after.
Simplified: Jazz - condenser, Rock - dynamic.
Usually it's a mix of both.

Regards
Kai
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polypals

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Re: "Breaking In" Mics?
« Reply #6 on: September 07, 2014, 08:45:27 am »

Your MO is not so much different than mine.
I get excellent results with Electro Voice RE 20 recording drum kit.

With Jazz, considerable lower volume and larger distance, the use of condensor mikes is no problem.

AKG 400 series are not my favourite. I consider it a sub standard condensor mike that can not meet the quality level Neumann KM or Schoeps Colette series mikes give.   
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soapfoot

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Re: "Breaking In" Mics?
« Reply #7 on: September 07, 2014, 10:53:38 am »

Enough dynamic alternatives that will do the job just as well saving the Neumanns for the purpose they are meant for.

Yeah, but I don't do too much diffuse field orchestral recording these days!

Condensers on drums can be great for rock or jazz. And jazz drummers do not always play with "considerably lower volume" than rock drummers. Not even close. Ever hear of a guy named Tony Williams? Far too many generalizations here to be useful in the world of music recording.

On-topic:

Anecdotally, some microphones do seem to me to change their sound over time in high SPL environments, though I have not done any empirical or scientific testing of this. I've never heard anyone allege that such changes are ever for the better. Ribbons sag and fatigue, and some moving coil dynamics can sometimes seem to change over time as well when continually subject to very high SPLs and air blasts.

At the component level, certain types of capacitors seem to change a bit after several hours in use, but this is a topic that is controversial and hotly debated. There has been some research and experimentation on the topic, though not, to my knowledge, of the peer-reviewed variety. Example:

http://www.diyaudio.com/forums/parts/81355-capacitor-burn-break.html

(You must be a member to view the images of oscilloscope traces).
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polypals

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Re: "Breaking In" Mics?
« Reply #8 on: September 07, 2014, 08:33:23 pm »

Mikes are positioned at greater distance recording a drum kit when playing jazz.
That reduces the sound level the mike reaches considerably. Makes the use of condensors possible.

I am under the impression large membranes are more vunerable to high SPL's than smaller capsules.
That is in line with measurement condensors designed to register high SPL's. They are quite small.

With the right EQ quality dynamic mikes do a good job close miking a drum kit.
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soapfoot

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Re: "Breaking In" Mics?
« Reply #9 on: September 09, 2014, 09:27:24 am »

Mikes are positioned at greater distance recording a drum kit when playing jazz.

Respectfully, I can only assume you're referring to your own studio, as this generalization does not apply (even 'in general') to what goes on in environments where I record, produce, and play.

In the studio where I do most of my work, we regularly spot mic toms with 414s, Gefell MT71s, and similar on straight-ahead jazz dates. Usually a FET 47 in front of the resonant bass drum head. Typically something close on snare as well. Sometimes the drummers play loudly, and there has been no noticeable degradation of any of the large diaphragm condensers to date. They're in daily use; both suites in the facility are in use an average of 28-30 days a month.

Coincidentally, besides producing, I make my living playing with jazz being sort of at the foundation of what I do, so I've had a chance to see how many different engineers set up for drums. There are many, many ways to get great sounding jazz recordings; I've been involved with projects using just a pair of U67s on the entire drum kit, to spot mics on every drum and everything in between. It's all within the realm of "common practice" as far as I can see.
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polypals

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Re: "Breaking In" Mics?
« Reply #10 on: September 14, 2014, 10:24:33 am »

I happen to be a lucky guy that still has the opportunity to record jazz both in studio and on location played by guys who are able to find a good acoustical balance. A natural sound from instruments is not registered with mikes only inches from the source.
It is a matter of taste as to what sound you are after. A jazz kit sounding like Billy Cobham is not my cup of tea. Ever heard of Rudy van Gelder?

I record 70-100 piece orchestra's in concert halls on a regular basis.
With me anything goes as long as it can be defined as music.
Years ago a bunch of gentlemen called Status Quo tried to blow up my hearing. They did not succeed.
Yes, I did all that but these days I try to select jobs where a natural sound and balance are valued.
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lilywebb38

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Re: "Breaking In" Mics?
« Reply #11 on: September 26, 2014, 04:52:55 am »

For musical instruments what you call "break in" is undoubtly very important.

A high quality condenser mic - on the other hand - is constructed with the goal that it should NOT change its sound over time.
For this purpose, some critical parts of it are even pre-aged.
So once it's delivered, its sound should stay the same for a long time.
Breaking in with sound of any kind (except explosions) for sure wouldn't change the mic.
Only environmental circumstances like very high temperature or excessive humidity or a combination of both can "break" - not "break in" - a mic.
I say "break" because every change is unintentional here.

Some electronic parts, specially electrolytic capacitors, can change a bit if in use after a long time with no power applied to them.
This is called "reformatting", because they where already "formated" in the factory.
The effect is very little and mostly inaudible, as those C's are usually not in the audio chain.
Plus - it's only necessary to put power on them to do this, no special signal required.

Regards
Kai

I had no idea that this was the case.  So is it safe to say that when dealing with low quality products it is highly likely that its sound will change over time? 
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klaus

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Re: "Breaking In" Mics?
« Reply #12 on: September 26, 2014, 12:36:59 pm »

The question is not specific enough for me to endorse its conclusion (in response to an equally nebulous post):
All electronic components drift with time, and deviate from their original value. This deviation is small enough in most cases that it is negligible. The fact remains that resistors change resistance, and capacitors and cables/wire have a short or lengthy break in period and, in the opinion of some, improve with time in their ability to transport audio (i.e. those that are in the audio chain of a mic- DC-coupling and FET source biasing capacitors etc.).

This process of change is not limited to low-budget mics, but is generally unavoidable (and in the case of capacitor or cable break-in, desirable).  I am unaware that low-budget mics use electronic components more prone to drift than used in high quality products.

The story gets more complicated with capsule diaphragms (their back plates are usually stable over time): Styroflex and PVC do age with time. And all diaphragms suffer from exposure to temperature and sound pressure extremes. To what extent this last scenario is a function of how much you paid for the the mic is questionable. Most low-budget Chinese mics use the same process of capsule manufacturing (including pre-aging) that is used in premium brands.
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polypals

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Re: "Breaking In" Mics?
« Reply #13 on: September 26, 2014, 07:49:12 pm »

In circuits negative feedback can to a certain extend compensate for changes in components.
Aging tubes give less amplification, passive components also change over time.
Please note negative feedback does not improve a poor design or inferior components.
Too much n.f. is bad for your ears.
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Kai

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Re: "Breaking In" Mics?
« Reply #14 on: September 27, 2014, 08:00:05 am »

negative feedback can to a certain extend compensate for changes in components... Too much n.f. is bad for your ears.
If you have a good design high negative feedback will not change something to worse.
The main problem that cannot be cured by NFB is a circuit that is too slow for the purpose it's build for.
A designer has to know or test the limits of his design to avoid that.
Unfortunately this art is dying out, and basic science partly replaced by esotheric "opinions" about certain build elements.

E.g. take the very common TL07x family of OP-amps and use a gain of more then 20dB.
Open loop gain (gain with no NFB) at 20kHz isn't much above those 20dB with a TL7x.
So NFB will not do it's job to linearize the resulting amp design, resulting in a poor HF performance.
Use a faster OP-amp and the same design will work flawlessly.
Use the same "better" fast OP-amp as buffer (gain=1 = 0dB gain) and it's very likely that it will start to more or less obviously oscillate, delivering very poor HF audio quality, because it's not build for beeing used for a gain of "1".


BT: most condenser mic's don't use much NFB in their design, specially tube and FET circuits have a bit of current NFB but no voltage NFB over several stages.
Very often there is only one active stage anyway, the tube or FET, so the signal path is quite short.
Not many electronic parts to "break in", mostly just the tube and the coupling cap in front of the transformer.
Exeption eg. Neumann U89 using a voltage feedback to equalize the HF.

Regards
Kai

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polypals

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Re: "Breaking In" Mics?
« Reply #15 on: September 28, 2014, 12:41:12 am »

Opamps often have more open loop gain than is needed.
Reducing 100 dB olg with80 dB nf is not sound design practise, no matter how fast the opamp  is. It leads to high amounts of transient intermodulation distortion. TID is bad for your ears.
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Kai

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Re: "Breaking In" Mics?
« Reply #16 on: September 28, 2014, 08:02:22 am »

Opamps often have more open loop gain than is needed.
Reducing 100 dB olg with80 dB nf is not sound design practise, no matter how fast the opamp  is.
Sorry, but this is not the case for usual cheap audio purposed OP-amps.
TL 07x eg. has an open loop bandwidth of ca. 45dB@20kHz, not much reserve for NFB in an gain or filter stage.
OP-amps generally have very high open loop gain (up to around 120dB), but only at DC or very low f.
They cannot be used without high NFB, or to say it better, high NFB is a working principle on OP-amps

nf is not sound design practise, no matter how fast the opamp  is. It leads to high amounts of transient intermodulation distortion.
TID doesn't come from NFB, but from circuits too slow to follow the signal, so that NFB cannot cure the distortion.
If TID appears an amp can be considered as faulty design, or used for the wrong purpose.

Higher NFB always gives cleaner signals as long as the whole circuit works within it's limitations.
This means with not too high frequencies or to much output current or voltage.

The question is, if high linearity is to be considered the goal or if certain types of nonlinearities are welcome to enhance the signal.
This is certainly the case with lot's of tube devices.

Regards
Kai
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Jim Williams

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Re: "Breaking In" Mics?
« Reply #17 on: September 29, 2014, 11:14:41 am »

072 type opamps with 40 db open loop gain at 20k hz will give you 25 of loop gain correction via negative feedback. That isn't much but they still show .001% or less THD at unity gain.

5532 and modern 'audio' opamps have 60 db OLG at 20k hz giving an additional 20 db of loop correction at 20k hz.

Some do better than that, the ADA4898-1 has about 80 db OLG at 20k hz, much better. The National LME series have about 75 db OLG at 20k hz. Combined with decent slew rates, CCIF IMD is at residual levels on the Audio Precison analyzer. That is .00015% or 1.5 ppm. I suspect it's even lower as it will not increase using noise gain techniques to expand the analyzer's measurement range.

Bob Pease of National did some tests using a network analyzer and some noise gain techniques on the LME49720 opamp. He determined actual THD was at -154 dbu once the noise was factored out of the measurements. In this situation, negative feedback is a beneficial effect as I know of no other active devices with errors that low.

In other words, a modern opamp is not a problem.  Nor do they need a break in period. Some film capacitors do and there may be some discussion on whether a plastic diaphram capsule may also need it, it is after all a film capacitor too.
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klaus

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Re: "Breaking In" Mics?
« Reply #18 on: September 29, 2014, 11:49:55 am »

The last two posts are WAAAY too esoteric for most participants of this forum. Could both of you please paraphrase, condense, and simplify their message?

Thanks!
KH
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Uwe

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Re: "Breaking In" Mics?
« Reply #19 on: September 29, 2014, 04:02:08 pm »

Neither of these Op-amp design topics relates to the original rather strange question of "Breaking In" microphones.

In a 50+ year career of intimate involvement with vacuum tube and solid state electronics, acoustics and transducers, I have yet to experience this phantom phenomenon so passionately described without solid scientific explanation, physical evidence or credible measurements. The need for tube warm-up is a different topic, as is the long term aging of some components. Operation of devices outside their design limits, for example exposure to excessive SPL may cause breaking them, not to be confused with "Breaking In".
"Breaking In" electronic devices is also advocated by various Hi-Fi enthusiasts who are convinced that running loudspeakers and headphones for several days with low level white noise conditions them and their connecting wires...

In short, "Breaking In" your microphones (or other transducers) has no verifiable benefits, but, aside from potentially shortening their life expectancy, does no harm.

Uwe Sattler,
Technical Director at Sennheiser Electronic Corp. and Neumann|USA (retired)
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klaus

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Re: "Breaking In" Mics?
« Reply #20 on: October 01, 2014, 12:36:48 am »

The breaking in of components and its possible effect on sound is a controversial subject, because the phenomenon- if it exists- is hard if not impossible to "verify" as Uwe mentioned, certainly with conventional electronic testing apparatuses.

Further discussion depends largely on whether we are willing to respect subjective impressions by those who claim they hear the difference. Which, in turn, pretty much eliminates skeptics from the discussion.

But skeptics do not like to be eliminated from discussing a phenomena which they do not regard as real; so they want to discuss the subject further, but with opponents whose opinions they fundamentally do not respect or accept. Likewise, believers in the break-in phenomenon do not accept the basic premise of the skeptics who deny its existence unless believers can produce scientific proof.

Two ways to deal with this issue remain, as I see it. Either you:

1. categorically deny the existence of any phenomenon which you cannot measure, or whose existence you cannot explain. If that is the case, you should stop arguing, let it be, and move on.

Or you:

2. experienced the phenomenon as real, and would like to learn more about its existence empirically, even in the absence of scientific proof rendered by current measuring devices. You wish to deepen your understanding of this phenomenon by sharing under what conditions, in what circuits, what voltage environments, with what components, etc. you have witnessed component break-in, and what effect the breaking-in had on the sound of the device.

I have experienced some, but no all, of the various types of breaking in a component discussed and reported in HiFi magazines. For example, I usually do not send out mics in which I have performed major circuit upgrades/restorations/repairs right away, but 'break them in'. In this case that means leaving the mics on under realistic conditions for two to three days, before I send them out.

The only difference I consistently hear is in broken-in capacitors when they are in prominent audio circuit positions (i.e. coupling caps). Breaking them in removes a bit of midrange harshness, I have found. How do I know that for sure? I have on occasion switched out a high quality coupling capacitor installed in a test mic, which has been in use on and off for ten years. When I install that capacitor in a similar mic which also uses the same exact model and vintage of capacitor- only new/unused up to that point- I hear immediately that the new one is harder and less musical compared to the broken-in part.

The only other component where I can hear a difference and where I  have made the same tests of switching-out the same brand, model, and vintage is the mic cable: I usually connect FET/solid state mics I work through a 25 foot Gotham GAC 3 cable to the mic pre and phantom source. Occasionally I switch out that mic cable with a brand-new, unused one from the same batch as the cable I have been using for the last decade or longer. It's terminated with the same high quality connectors and has the exact same length.
Here, too, I recognize a smoother midrange in the broken-in cable (the rest of the frequency range and the dynamic behavior seems unchanged). The difference in midrange resolution is not as stark as with capacitors, but it improves in the same way: better connection to the music, with less artifice in the way.

I cannot extrapolate my experience with breaking in these two types of components to others, where I have not heard differences. And I do not expect or need others who read this to be able to duplicate my experiences. But I will continue to follow through with breaking in components whenever I think they make a positive audible difference in outcome.

P.S.: To finally address the original question: I have not heard an improvement in the sound of condenser capsule membranes with time or usage.
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hasbeen

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Re: "Breaking In" Mics?
« Reply #21 on: October 07, 2014, 08:39:07 pm »


The only other component where I can hear a difference and where I  have made the same tests of switching-out the same brand, model, and vintage is the mic cable

I cannot extrapolate my experience with breaking in these two types of components to others

I am trying to wrap my mind around the mic cable phenomenon.

When you say "I cannot extrapolate" does that mean you have no explanation as to why a 'broken in' mic cable sounds different from a new one?
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klaus

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Re: "Breaking In" Mics?
« Reply #22 on: October 07, 2014, 09:22:23 pm »

Sorry, I was obviously using language that was too sophisticated for my own good, i.e. muddled.

I meant to say: what I have experienced with break ins of capacitors and mic cable, I would not automatically assume to be valid for other types of equipment which I have not tested the break-in hypothesis on.
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Klaus Heyne
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hasbeen

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Re: "Breaking In" Mics?
« Reply #23 on: October 08, 2014, 09:45:58 pm »

Sorry, I was obviously using language that was too sophisticated for my own good, i.e. muddled.

I meant to say: what I have experienced with break ins of capacitors and mic cable, I would not automatically assume to be valid for other types of equipment which I have not tested the break-in hypothesis on.

Still, I am interested to hear your thoughts as to why a broken in mic cable might sound different than a new one?
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boz6906

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Re: "Breaking In" Mics?
« Reply #24 on: October 09, 2014, 09:17:22 am »

I suggest 'Dielectric Fatigue' makes the cable's velocity of propagation non-linear over a varying voltage...

DF would also affect the capacitance of the cable as the signal changed, dynamically changing the cable's HF attenuation.

Maybe...

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5310594&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5310594


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Jim Williams

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Re: "Breaking In" Mics?
« Reply #25 on: October 09, 2014, 11:24:33 am »

Propagation delay in cables are measured as a percentage of the speed of light.  70% is a good spec if it's linear vs frequency. Most audio grade cables will show drop-offs at higher frequencies.

Besides high end Kimber silver I use Belden 9182 LAN network cable here for mic connections. The reason is propagation delay at 70% up to multi-megahertz, 8 pf per foot stray capacitance, heavy 22 awg FEP teflon insulated wires and 150 ohm impedance. It also sounds very good too.

In 1994 I brought some rolls down to Paramount Picture's foley building for the AE's to try out. They ended up wiring the entire building with it even thought they just repaired the building after the 1994 quake. The AE's demanded it so it was installed.

I brought some rolls of it to Ray Kimber's factory in Ogden, Utah. Ray has a great lab with nice test gear like HP network analyzers and such. We compared it to his pure silver AGSS 19 awg stranded 3 braid. Tone was revealing on both but the silver had that little extra detail. The largest difference was background noise, the AGSS is silent even though it's a 3 braid, not a traditional coax design.

That background noise I hear in every other audio screeened cable, including the Belden 9182 LAN cable. You have to audition Ray's stuff to understand that we have all accepted cable noise our entire lives. Only when it goes away do you realize we have pushed that noise out of our minds while working. When it goes away it gets your attention.
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klaus

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Re: "Breaking In" Mics?
« Reply #26 on: October 09, 2014, 06:00:57 pm »

Still, I am interested to hear your thoughts as to why a broken-in mic cable might sound different than a new one?
I really do not have any thoughts worth posting. This field is new, and controversial, as far as scientific explorations into it are concerned. Remember, we are still in a time period where a reputable audio engineer (and the then-importer of a well-respected recording device) put on a seminar at the University of Berkeley, to prove that lamp cord sounds exactly the same as a high quality speaker cable.

I am confident, that, as measuring technologies advance, we will find out what molecular or other changes occur in a cable over time.
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Re: "Breaking In" Mics?
« Reply #27 on: October 09, 2014, 06:46:47 pm »

A lot of differences in audio cannot be explained with measurement methods well known and accepted.
Compare a solid state power amp with a tube amp both with similar frequency response and distortion specs. I am pretty sure the tube amp wins.
The conclusion tube electronics are better is not correct. We simply do not have the right parameters to compare.

There is only one valid means to use, that is our hearing. That does not make the job easier.
On the other side most people who listen to recordings give way to their brain to make up for any deficiences. It is just a bunch of professionals that are bothered. These are the people who do not accept shortcomings and keep trying to improve the process.
They often have to stand up to engineers and designers that do not understand the findings of  professionals gifted with good hearing.
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Uwe

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Re: "Breaking In" Mics?
« Reply #28 on: October 09, 2014, 09:59:14 pm »

The process of hearing is highly subjective and involves unprovable biases and psycho-acoustics. I still say that a repeatable measurements are worth a thousand 'pseudo expert' opinions. The assumed changes over time (not to be confused with breaking-in) of dielectric properties in any cable conducting electrical signals would be far too small to have any effect at any property for audio frequencies (frequency response or phase), period!
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polypals

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Re: "Breaking In" Mics?
« Reply #29 on: October 10, 2014, 06:19:23 pm »

Human hearing is the most valuable if not the only instrument to judge quality of equipment.
To degrade human perception as subjective and influenced by bias and psycho acoustics is nonsens.

Blind tests based on scientifically and statistacally respected methods give reliable conclusions.

These are not to be confused with a line up of twelve loudspeaker pairs that can de selected at random without even compensating for efficiency. 

Please give me one measurement that predicts the perception of what the human hearing registers.
Leave out transducers, that field is even more complicated. Lets narrow the case down to analogue amplifiers.
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Jim Williams

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Re: "Breaking In" Mics?
« Reply #30 on: October 11, 2014, 12:14:28 pm »

Please give me one measurement that predicts the perception of what the human hearing registers.
Leave out transducers, that field is even more complicated. Lets narrow the case down to analogue amplifiers.

How about THD+noise? Most people can detect that after about 2~3% in transistor amps with odd harmonic partials. Some do better but have more experience in detecting these errors.

The problem with euphonic selective analysis are the results are in the ear of the beholder. Everyone's hearing is different, everyone's ear shape is different, everyone's taste is different.

Objective tests avoid those variables. Test gear will work very well in finding errors. It will not tell you what you like to listen to.
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Uwe

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Re: "Breaking In" Mics?
« Reply #31 on: October 11, 2014, 01:54:50 pm »

"To degrade human perception as subjective and influenced by bias and psycho acoustics is nonsens.
Blind tests based on scientifically and statistacally respected methods give reliable conclusions."

And yet, it is exactly properly conducted (double) blind test which have convincingly debunked the pseudo scientific claims for practically all snake oil claims for the affect of cables, line cords and connectors on audio transmission and perception...
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polypals

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Re: "Breaking In" Mics?
« Reply #32 on: October 11, 2014, 07:26:31 pm »

Thanks Jim for your suggestion.
I have to admit my carreer in audio started when vacuum tubes were still being used, not only in high grade microphones.

Soon after the introduction of solidstate amps we found these had to have THD figures at least ten times better than the ones found in tube amps to get similar audio quality.
So much for measurement that gives results on which can be predicted how amplifiers sound.

Noise can be measured and compared, no problem with that.



Uwe,

I am not talking about esoteric gear like cables with silver and gold conductors, parts that were given the cold treatment and so on.

My thesis is about allowing our ears to judge new equipment as final test before this gear is accepted for professional use.
This prevents the kind of disasters I witnessed working for a major record company that had its mixers constructed in house. In house to be understood as designed and made by a sister company.

A junior balance engineer, younger and handsomer in those days. With a collegue we were comparing a
power amp design made by me in one of the control rooms of the studio.
We compared the new design against the standard monitor amp.
To adjust the output levels we used the mixing console just to correct the sound level.
After several hours I found a discrepancy in what we heard. We used other channels more strange things happened.
I suggested to my colleague the channels had audible differences. He laughed hard and said you lost your hearing after too many hours testing, this is state of the art equipment. Impossible.

Next weekend we started from fresh listening to the various channels of this mixing console.
In a blind test I could identyify several channels.

The studio manager heard what we had discovered.
He asked if I could set up a test to proof what we discovered.

What did I need? A maintenance engineer that could align three channels from various generation mixing consoles to give exactly 0 dB amplification. We had a small box containing a threefold selector switch.
The new power  amp design was used with a standard monitorspeaker to play a selection of records, no masters just LP records.

The test was so convincing all my colleagues from recording picked the correct generation channels.

My point is: We are all interested in achieving good audible results for recorded music. Forget about hi fi.
With some exceptions most recordings sound more impressive than the live performance, with an exception for some classical recordings.

Please answer this question:
How could a leader in the industry in those days end up with expensive gear that was unsuitable for professional use?


Please note.
Although this happened several decades ago I choose to be discrete and do not mention the company or persons involved.
Just drop me a PM if you want more information.

 
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David Satz

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Re: "Breaking In" Mics?
« Reply #33 on: October 14, 2014, 09:14:56 am »

polypals, we each make our observations and form our opinions. Human nature is to pay more attention to those occurrences which reinforce our own expectations and beliefs and our sense of how wise and knowledgeable and experienced we are. As a result, each of us will tend to feel well justified in what we believe, and to think that we know better than anyone who would disagree with us.

If audio is your hobby, there's really no reason ever to burst that little bubble. It is very pleasant to live there; many people do. I don't mean to say that you're in that bubble while I am not--although admittedly that is what I tend to feel when I read your posts. I can only expect that you would feel similarly if I posted my (very different) opinions, if you were to read them.

The problem is that neither of us, relying solely on our own senses and intuition, can tell at a given time whether we are inside the bubble of "confirmation bias" or not. We should therefore realize that we will probably tend to feel that we are right (and smarter than others) and that the other is wrong (and we are smarter than them), irrespective of the actual facts. Our senses and intuition give us absolutely necessary, but not sufficient, information for recognizing what we can consider to be true. People fool themselves all kinds of ways when they ignore that distinction.
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polypals

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Re: "Breaking In" Mics?
« Reply #34 on: October 14, 2014, 12:43:49 pm »

Thanks for your observations that are touching filosofical areas.

Again I read reluctance to trust human perception. What gives engineers reason to trust the human ear? If I compare this attitude to photography no professional photographer distrusts his eyes.

I know amongst amateurs there is a lot of gimmicking that is not based on sound research and tests.
To conclude this attitude exists likewise amongst professionals is to say it mildly incorrect.

In the early seventies there was a trend to cut records without using tape.
Guys interested in hi-fi agreed these records sounded much better than records that were recorded on tape. During those sessions I once played these records over tape, straight from the playback amp from the recorder. Nobody in the audience noticed this.

I am well aware that suggestion and incorrect methods to compare equipment auraly can give unreliable conclusions.
Still I defend the habit to judge new developments with my ears.
After all we are all interested to get better aural results.
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Jim Williams

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Re: "Breaking In" Mics?
« Reply #35 on: October 14, 2014, 01:11:55 pm »

Thanks Jim for your suggestion.
I have to admit my carreer in audio started when vacuum tubes were still being used, not only in high grade microphones.

Soon after the introduction of solidstate amps we found these had to have THD figures at least ten times better than the ones found in tube amps to get similar audio quality.
So much for measurement that gives results on which can be predicted how amplifiers sound.
Noise can be measured and compared, no problem with that.

This is why I said "odd partials" as transistor amps tend to have a bit more 3rd and 5th harmonics than a decent tube power amp which is dominated by euphonic 2nd and 4th harmonics. Most listeners will accept 5% THD from a tube power amp if the harmonics are even ordered, those tend to add a musical 'air' to the sound many find pleasing = euphonic response. I call that the 'aural excitement' effect.  It's also why we electric guitarists prefer tube guitar amps.

Transistor amps require very low THD+noise specs as any odd harmonic partials are easily detected by the listener. You also have other factors like slew limitations affecting the transient response.

Since both topologies have been well designed and developed, it's now really about personnal taste as you can get very accurate transistor power amps and there are some tube power amps with decent specs that also sound rather neutral, the Futterman designs come to mind.

With modern test gear like Audio Precision, one can now days measure and predict with some success the sound of these designs.

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polypals

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Re: "Breaking In" Mics?
« Reply #36 on: October 14, 2014, 05:32:31 pm »

Sorry Jim, I do not agree with even/odd harmonics theory.

It depends on what tubes are being used what kind of harmonics are generated.
Triodes give even harmonics, penthodes generate odd harmonics.

In poweramps the distortion generated by the output triodes will be virtually zero provided the output tubes are paired.

I wonder about the 5% figure you quote. Any amp with that amount of distortion no matter what harmonics the 5% consist of is unsuitable for monitoring.
A decent tube amp gives less than 0,1 % harmonic distortion at 1000 CS.

Audio Precision makes excellent gear to measure and analyse distortion.
Nevertheless it is only possible to measure and predict only with limited succes how equipment sounds.





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Jim Williams

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Re: "Breaking In" Mics?
« Reply #37 on: October 15, 2014, 11:22:45 am »

There is measureable THD in matched push-pull tube output devices. That is why negative feedback is applied to reduce it. Modern test gear like Audio Precision has residual THD at -120 db, far below these amps. It's easy to find and measure. Throw the CCIF IMD tests on them and you find other errors like slew limiting.

As I said it's really down to personal choice, I find a very fast current feedback transistor amp design reveals more than the tube/transformer designs do, at least to me. The same applies to mic amps, I prefer the transistor stuff for total accuracy, the tubes for some euphonic treatment. Each has their place.
YMMV.
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polypals

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Re: "Breaking In" Mics?
« Reply #38 on: October 15, 2014, 06:19:10 pm »

Jim.

You missed the point I was describing a power amp with output triodes.
With paired output tubes the distortion from the output tubes is virtually zero.
That is a simple matter of mathematics.

Im refering to power amps from the golden age of American design.
Take the Harman Kardon 11 amp. The output tubes are applied half way between penthode and triode inh ultra lineair mode.
This amp uses video penthodes as drivers to assure wide band amplification. That makes NFB in multiple loops possible without risking stability of the amp. One of the best tube amps I ever listened to.
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klaus

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Re: "Breaking In" Mics?
« Reply #39 on: October 16, 2014, 03:20:21 am »

Please keep topics microphone-related, and whenever there is an off-topic argument to be discussed, especially one that may be  outside the interest of most microphone users, please PM each other.
Thanks.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com
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