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Author Topic: Driver breakin  (Read 1966 times)

Ivan Beaver

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Driver breakin
« on: December 12, 2013, 07:47:04 pm »

This topic comes up a fair bit-and I have never seen any data one way or the other.

So I decided to take some before and after measurements.

Attached is a shot.  The purple is before and green is after.

Yes there is a difference-but it is pretty small.  Is it enough to be concerned with or audible?

I will let you decide.

I tried hard to make sure that nothing changed between measurements.

The break in procedure was 20Hz with 30V input for 3 hours.  Would longer make any more difference-I am not sure-but this was all the time I had for the test.

Just thought I would share this little test.
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Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Ales Dravinec

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Re: Driver breakin
« Reply #1 on: December 12, 2013, 11:55:37 pm »


The break in procedure was 20Hz with 30V input for 3 hours.


Ivan,

I expected 'more' after burn-in I suspect the coil was still warm(er) when you took the 'after' measurement ?
Both measurements are equal at frequency, where impedance is high, I guess port must kick in there somewhere ??

Thank you for sharing. I'm a bit ashamed I never did this myself.

Respectfully

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Nicolas Poisson

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Re: Driver breakin
« Reply #2 on: December 13, 2013, 04:31:59 am »

I have been told the speaker suspension becomes more flexible after break-in, and that the speaker outputs less but goes deeper. Looking at Ivan's measurement curves, the difference appears anecdotic to me.
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Ivan Beaver

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Re: Driver breakin
« Reply #3 on: December 13, 2013, 07:40:40 am »

Ivan,

I expected 'more' after burn-in I suspect the coil was still warm(er) when you took the 'after' measurement ?
Both measurements are equal at frequency, where impedance is high, I guess port must kick in there somewhere ??

Thank you for sharing. I'm a bit ashamed I never did this myself.

Respectfully
This was in a short tapped horn.

The "new" transfer measurement was made with around a 3V input.  Then I used a separate generator to drive the 20Hz tone (so I would not do any adjustment to the measurement/generator system), then switched the input to the amp back to the 3V (or so) measurement generator.

I did let it cool down maybe 30 minutes before retesting.

I am not saying this is an absolute test-and yes the break in period could have been a lot longer-and I should have let it cool down overnight-to be exact.

But I had a rare little period of time to do some "playing" and just wanted to share what I found and the parameters of the test.

Other test could be different.

This was done inside the warehouse-with the mic about 1M from the cabinet in a ground plane configuration.

I don't think any objects were moved around that would affect the reflections-but there might have been.
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Tim McCulloch

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Re: Driver breakin
« Reply #4 on: December 13, 2013, 08:00:32 am »

Thanks for posting this, Ivan.  I've long thought that "break-in" was a criminal act, not a loudspeaker thing.  Your measurements appear to confirm this.
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Kevin Graf

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Re: Driver breakin
« Reply #5 on: December 13, 2013, 10:54:54 am »

Dick Pierce an audio consultant wrote this way back in 1996:

>My question is two fold: why would speakers need breaking in ?  Is
>anyone aware of any measurements and tests having being done of before
>and after performance that has shown a measurable difference?


I am aware of at least one person who has done extensive measurements
of this type: me. I have a database of several thousand drivers that I
have measured.

>I have been able to think of only one mechanism attributable to the
>speaker that to me could conceivably be at play if there is indeed an
>effect. It is that the elastomeric materials that form the suspension
>of the cone of a driver are somewhat stiff to start with and become
>more pliant through use, thereby allowing the cones of the drivers to
>move more freely with use.

>I don't believe this though, as an elastomeric material that exhibited
>such a change in properties would surely continue to 'loosen' over
>time so as to go beyond the point of aurally optimum elasticity so
>that there was an eventual degradation in sound quality such as when
>the voice coil made some unwanted high speed excursions into
>stationary bits.


Well, there are, indeed, several mechanism that are, indeed, at work
that cause the operating parameters of drivers to change through use.
However, the notion that once one gets a speaker home it requires
"breaking in" suffers from several problems.

First, as a driver comes off the line, it's actual performance if
fairly far from it's intended performance target. Reasons for this
include the fact that the centering spider, typically manufactured
from a varnish- impregnated linen, is far stiffer than needed. Working
the driver back and forth lossens the spider considerably.

Now, one might say: there's objective proof of the need to "break in"
a loudspeaker! Not so fast. The break-in period for the spider is on
the order of several seconds, and if it takes you several seconds or
minutes or whatever once you get the speakers home to loosen the
centering spdier, it's not proof of the need to break thme in, it's
proof that the speaker you just bought HAS NEVER BEEN TESTED!

But, on to other points.

When I measure a driver, I can see a significant change in a variety
of operating parameters as the speaker is driven. Usually, in woofer,
the resonant frequency drops as the speaker is used, often by as much
as 10-20%. This is due, as you suggest, to a relaxing of the
elastomers used in the suspension.

However. If I turn the stimulus off, within a few minutes most, if not
all, of the change has completely recovered, and we're back to go
again.  The elastomer has recovered from it's stresses (this is
especially true of certain polybutadene-styrene surround
formulations).

There are plenty of other, real, physical changes. For example, one
can see a reduction of the electrical Q with time under heavy use,
simply because of the positive temperature coefficient of the
resistance of the voice coil. Allow the speaker to cool down, and it's
completely recoverable.

Get it hot enough, and you might permanently loose some flux density
in the magnet. But you have to get REAL hot to do that. Hotter than
most of the compounds used in making a speaker can endure without
catastrophic failure (damned few glues, varnishes, cones and
insulating materials can withstand the temperatures neede to reach the
Curie points of the typical magnetic materials found in loudspeakers).

>What I really think is at play in all this is the adaptive signal
>processing abilities of the brain.  It is not the speakers which get
>broken in, rather it is ones 'ears'.


When this has been suggested, despite the fact there's about a century
of research backing it, it is more often than not greeted with jeers
and cries. See, you can't sell special "break-in" CD's if the speakers
aren't broken in.

>I would be interested to hear other opinions on this.

Well, there will be loads of opinions. However, actual data on several
thousand drivers don't seem to give two shits about opinions, the
usual claims of "mysterious unmeasurable quantities" notwithstanding.

--
|                Dick Pierce                |
|     Loudspeaker and Software Consulting   |

11/2/1996
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Tim Perry

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Re: Driver breakin
« Reply #6 on: December 14, 2013, 12:38:51 am »

Thanks for posting this, Ivan.  I've long thought that "break-in" was a criminal act, not a loudspeaker thing.  Your measurements appear to confirm this.

I have long thought that that transducer break in was in the subjects ears and or perception.

I found this 2005 article of interest. http://www.audioholics.com/loudspeaker-design/speaker-break-in-fact-or-fiction
 
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sam saponaro

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Re: Driver breakin
« Reply #7 on: December 27, 2013, 07:10:41 pm »

I know guitar speakers sound slightly harsh and hashy sounding till you beat um up a little.I know guys go as far as spraying the cones with fabric softener and running a 60cycle hum from a variac through um for hours and some remove the outter doping from the surround.Warren Haynes I guess blasts music trough his Marshall cabs for something like 24hrs to break um in.
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John Halliburton

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Re: Driver breakin
« Reply #8 on: December 28, 2013, 10:27:17 am »

I know guitar speakers sound slightly harsh and hashy sounding till you beat um up a little.I know guys go as far as spraying the cones with fabric softener and running a 60cycle hum from a variac through um for hours and some remove the outter doping from the surround.Warren Haynes I guess blasts music trough his Marshall cabs for something like 24hrs to break um in.

Except now you've gone into the deep end of speaker superstition pool...yes, it may change the sound running the driver through the wash, but it's really-really-really a subjective area.

Also, any comparisons made involving a cold or hot voice coil are not part of the equation, that's a different phenomena unrelated to possible "break in" issues with a driver.

Best regards,

John
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Tim McCulloch

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Re: Driver breakin
« Reply #9 on: December 29, 2013, 02:24:07 pm »

Except now you've gone into the deep end of speaker superstition pool...yes, it may change the sound running the driver through the wash, but it's really-really-really a subjective area.

Also, any comparisons made involving a cold or hot voice coil are not part of the equation, that's a different phenomena unrelated to possible "break in" issues with a driver.

Best regards,

John

The only thing "breaking in" is the truth.  And the truth is that for professional audio loudspeakers, "break in" is voodoo bullshit, par excellence.

Break-in?  Plug them in and use them.  There, you're done.
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