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Author Topic: "Breaking In" Mics?  (Read 11838 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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Klaus Heyne
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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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