Speaker Break-In and Environmental Measurements

[ctrl]

Yesterday I stumbled across a YouTube video about break-in of guitar speaker drivers (the test conditions and reproducibility of the measurements can certainly be debated, but on the whole I think the test is valid).

IMO this video shows the difference between break-in (minimal change in driver FR) and wearing out a driver. The driver is a 12'' Celestion Vintage 30, which would be used as a midrange driver up to 1kHz in a loudspeaker design (theoretical).

After 30 hours of really extreme break-in of the driver - distorted guitar sound with around 130dBA@1m SPL - there is hardly any change in the frequency response up to 1.4kHz (blue is before break-in, green line about 1.4kHz):

Source: YouTube video linked above

Such a driver would be used up to a maximum of 1kHz (likely XO around 700-800Hz) in a "normal speaker", so that anything above 1.4kHz with a fourth-order filter already shows more than 25dB SPL drop - so nearly no change in FR at all in the usable range of the driver.

Most changes occur above 2kHz, where the driver is no longer guaranteed to move in a piston-like manner (first resonances occur much earlier) and will show corresponding break-up resonances - such as concentric and circumferential modes, rim contour and surround modes/resonances:

Source: High Performance Loudspeaker - Martin Colloms and Paul Darlington

By using distorted guitar tones as a test tone, practically the entire mid and high frequency range is stimulated.
Due to the extreme test conditions and the excitation of the break-up resonances at full SPL (or nearly full SPL), the first material changes occur in the frequency range of the resonances.

This would not occur with a hifi loudspeaker (apart from a single driver full-range loudspeaker) as the crossover prevents the break-up resonances from being excited at high SPL.

After the driver had been "tortured" for 300 hours with the extreme test tones, there were clear changes in the frequency range above around 1400Hz (again, blue is before break-in):

Source: YouTube video linked above

In some cases, new resonances have been added or have increased significantly. I would assume that these are signs of wear out off the driver material due to the excessive strain caused by the 300 hours of extreme sound reproduction.

Even under these extrem conditions, the change up to 1.4kHz is rather small and the SPL deviation should be around or below the manufacturer's standard deviation - +-1dB SPL deviation compared to a reference FR during production is not unusual).
(The approximately 1dB SPL difference in the frequency range of 20-1400Hz might be caused by a measurement/calibration error)

 

[suttondesign]

I strongly doubt it is possible, as a practical matter, to control driver measurement for temp, humidity, atmospheric pressure, inherent material and mfg variation, and probably other factors as well. But even worse, the human apparatus, which probably varies owing to many of the same factors, esp the time of day after ears have been pummeled for hours in streets and buildings. I know that even my mood and caffeine make a difference. And whether my house systems are running, or cars are rumbling nearby.

the equipment I have today, esp the transducers, are hugely better than what I could get in 1985, quite a bit better than 2000. Seems like we are close to the point where it’s external factors that matter most, dwarfing the transducer-affecting factors above when it comes to the best-engineered speakers.

all of which is to say, measuring a mid-run production driver unit in a fairly typical environment ought to be quite sufficient to indicate a product’s capabilities within a margin of error that is acceptable for even the best-trained listener. also, anyone over 35 has such compromised hearing, plus unique physiology, that the best we could ever hope for is indicative test results. which is why asr, erin, mab, and others are altering the industry.

I will say, despite my intermittent tinnitus and other factors, I know precisely the limitations of my DIY dipoles, as well as their strengths, just as I do those of the dutch 8c, which are my favorite marketed speaker of all time, and many other speakers I have owned or heard over decades. that is, I can readily hear and evaluate these differences, and it ain’t driver break-in issues. It’s big stuff. (I do poke the mid drivers of the dipoles from time to time to check the surrounds for stiffness or cracking, but that’s about it.)

my musings.

 

[Deleted member 48726]

All moving mechanical devices change their performance with;
-Use
-Temperature
-Relative humidity
-Air pressure
-Add to this heat in voicecoils for speaker drivers, as B&O has demonstrated

I worked quite a bit with car audio many years ago and, even though I have no measurements, that heavy woofers change their sound according to the above and from when new to after being used. Mind you this is not the everyday HiFi drivers.
Extrapolate from this and you get varying degrees of "break in" in other drivers as well. As such is physics.
In some cases it will be audible, in some cases not.

Like most things this is not a black or white topic.

 

[Mnyb]

I put it the fridge only to show that 10 mins in a cold environment has a much larger effect than 6 months of use. My intent is to show a brief stint in cold or moderate heat will produce changes similar or even larger than the measured break-in. Yes, a longer stint in the fridge, or a larger and more realistic heat load simulating hot motor would also make much larger changes. But, the point here is break-in is small compared to mild temperature swings.

We that lives in colder climates may be victim to this in a finished product . Your new speakers has been on a truck or in your own cold car for a long time so all drivers the whole box and the xover is freezer cold when you unpack

But that’s it’s own topic , putting the whole speaker in the freezer ? Did not some of amirm measurement of Neumann speakers show differences explained by the temperature in the room while measured?

 

[Multicore]

The market for audiophile HVAC may be underdeveloped. I know quiet systems are important for concert halls but surely we can do better than measuring noise. There must be scope to enhance the musicality of the mix and configuration of listening gases at home.

 

[Deleted member 48726]

The market for audiophile HVAC may be underdeveloped. I know quiet systems are important for concert halls but surely we can do better than measuring noise. There must be scope to enhance the musicality of the mix and configuration of listening gases at home.

I hope your home HiFi lives in a more stable climate than a car cabin and thus are not succeptable to as many variables.

 

[Deleted member 48726]

Accelerated Life and Power Testing

www.klippel.de

The figure to the left shows the variation of the stiffness of a spider versus measurement time measured by using the SPM module. After 10 hours of operation in the large signal domain, the stiffness at the rest position is decreased to 40 % of the initial value while the stiffness at high excursion is almost constant.

 

[Head_Unit]

Fs directly after assembly was 57Hz and after sweeping in free air at 18 Vrms for around 10mins (to check robustness of the assembly) the Fs dropped to 49Hz.

(1) How much time passed between the end of the 18V, and the 49 Hz measurement? Had the assembly cooled off (not that it should affect the suspension really)
(2) How about tweeters? (And by the way when those Uni-Q woofers move in and how just how much does it modulate the tweeters response?)
(3) Are your crossovers still making our amplifiers twice as powerful?!? (I once kidded Richard Small about that when he was at Harman...but actually considering the behavior of so many amplifiers, it was fairly true).
(4) OK back to the real topic, the 57 to 49 drop, how much would that actually change the response in the box? And is that really audible?
Grazie!

 

[Head_Unit]

listening gases

Isn't that more to do with what you eat/drink than the HVAC?

 

[MAB]

(1) How much time passed between the end of the 18V, and the 49 Hz measurement? Had the assembly cooled off (not that it should affect the suspension really)

@jackocleebrown this is important. Did you measure the driver right after the 10 minute stress, or did you wait a few hours?
It does take hours for a woofer to cool back down, for instance a peerless that took more that 3 hours to cool to equilibrium with the room, and most of the F9s) F(s) change after stress was heat, not break-in!!!:

Here is a Seas woofer that took at lest two hours to re-equilibrate with the ambient temperature:

Do Audio Speakers Break-in?

I have a brand new woofer that I got as a replacement, the original was defective. The replacement driver has been sitting around un-played. Seems like it is time to see how it changes with 'break-in'. I got a DATS recently, so I'll use that. I did check it against an HP LCR with a bias...

www.audiosciencereview.com

@jackocleebrown did you allow several hours for the driver you measured post-stress to cool?
If not, the heat of operation at 18V will take time to dissipate, and as you can see will cause a much bigger change in F(s) than break in phenomenon.

 

[Multicore]

Isn't that more to do with what you eat/drink than the HVAC?

That is indeed a factor. But I was thinking in terms of marketing a new class of product. If careful control of the exact chemical composition and metallurgical crystal structure of speaker cables is worth top $ then why not also the exact composition and purity of the gasses conveying the acoustic signals from speakers to ears? If that's too hard to sell then perhaps closed over-ear headphones with control of the gasses in the enclosed space? At the very least shouldn't there be audiophile humidification? Surely the composition of water vapor in the listening room is at least as much a factor as the alignment of crystals in a cable. </joke>

 

[Head_Unit]

perhaps closed over-ear headphones with control of the gasses in the enclosed space?

Hey we should go into business together and resurrect "Smell-O-Vision" for home use! And somehow we can also tie in to the medical marijuana market for some of the smell! And repurpose "cable risers" into "leaf risers" for the plants! Riches galore await! Has anyone noticed I love exclamation points!!!!

 

[Head_Unit]

the heat of operation at 18V will take time to dissipate, and as you can see will cause a much bigger change in F(s) than break in phenomenon.

Well, but how is internal heat of the voice coil/magnet affecting the stiffness of the spider(s) and surround? I mean I can imagine *some* effect from ambient air temperature on fibers and resin blah blah however I cannot conceive the effect would be very much at all. The worked stiffness taking time to re-stiffen, that is imaginable.

 

[Deleted member 48726]

Well, but how is internal heat of the voice coil/magnet affecting the stiffness of the spider(s) and surround? I mean I can imagine *some* effect from ambient air temperature on fibers and resin blah blah however I cannot conceive the effect would be very much at all. The worked stiffness taking time to re-stiffen, that is imaginable.

Accelerated Life and Power Testing

www.klippel.de

The figure to the left shows the variation of the resonance frequency fs and the variation of the voice coil temperature ΔTv versus measurement time t during long-term testing in a climate chamber where the ambient temperature has been changed by 50 degree.

 

[Head_Unit]

The figure to the left shows the variation of the resonance frequency fs and the variation of the voice coil temperature ΔTv versus measurement time t during long-term testing in a climate chamber where the ambient temperature has been changed by 50 degree.

That's 180 Fahrenheit swing! OK under those conditions sure I can imagine the stiffness changing, even catching on fire or freezing and cracking ha ha. Now under real room variations it looks like the Fs change would be a few percent, which is pretty tiny as I'd expect. I wonder what driver they tested?

 

[MAB]

That's 180 Fahrenheit swing! OK under those conditions sure I can imagine the stiffness changing, even catching on fire or freezing and cracking ha ha. Now under real room variations it looks like the Fs change would be a few percent, which is pretty tiny as I'd expect. I wonder what driver they tested?

It's an accelerated life test! It is very extreme.
This paper and figure are about testing to fail aka wear-out. Which is different than break-in. It's not a realistic use condition, it is set up to induce wear-out in a short period of time under highly accelerated use conditions. This way they can build a reliable product that will last a specified number of years in the field under certain use conditions.
The figure dose illustrate that temperature modulates the parameters.

Important to note, these reliability white papers by Klippel do indicate changes in driver parameters at iso-temperatures after these stress tests (after the driver has settled to control temperature), but they are not break-in, they are drivers that have been worn out.

 

[Deleted member 48726]

It's an accelerated life test! It is very extreme.
This paper and figure are about testing to fail aka wear-out. Which is different than break-in. It's not a realistic use condition, it is set up to induce wear-out in a short period of time under highly accelerated use conditions. This way they can build a reliable product that will last a specified number of years in the field under certain use conditions.
The figure dose illustrate that temperature modulates the parameters.

Important to note, these reliability white papers by Klippel do indicate changes in driver parameters at iso-temperatures after these stress tests (after the driver has settled to control temperature), but they are not break-in, they are drivers that have been worn out.

I know. But it's the same thing just on the other side of the coin. As I wrote earlier this is not a black or white thing. As drivers are made 10.000 different ways by 1.000 different materials in 30 different sizes. Break is not a myth. It's just a question of it being audible or even enough to care about in design phase of your speaker. Definitely not something to care about with your average Dynaudio living room speaker.

 

[Salt]

Why worry about break-burn-wear-in?
Doing some of the recommended procedures won't do no harm (if done properly), and if they help for whatever: why not?

Anecdote:
my first speaker with MSW (Manger Schall Wandler) took a lot of time to be finished, and at first listening sounded worse than a LS3/5 ever would.
Checking the crossover gave no error, cables and polarity were correct ... so I dragged them back into the basement, there polarity reversed and face to face positioned with a blanked over all they were treated by noise over night, and the next day it was at it should be ....
The MSW may be outstanding in this aspect as elasticity is the central point of sound reproduction, but since then I give some time for whatever burnbreakwear-in.
Does cost neither arm nor leg, and if helpfull, helps, if not, does no harm.

 

[MAB]

Why worry about break-burn-wear-in?
Doing some of the recommended procedures won't do no harm (if done properly), and if they help for whatever: why not?

Because the recommended break-in procedures to often come from YouTube, or a dealer. If you follow the advice that pervades YouTube, you may play them loud enough and long enough to wear them out. If you follow the dealer's advice, you will enter a circle of confusion and believe all sorts of things happen with your sound that don't.

Also, because Kef just recently wrote on their website misinformation about speaker break-in, phrased in the usual audiophile terms. When in fact environmental temperature changes in a room are larger effects than break-in.

And people are citing Klippel long term reliability and accelerated stress testing papers in this thread, confusing wear-out tests with break-in, which shows that we actually do need to talk about speaker break-in. And because people repeatedly misquote the physics of what actually happens during break-in. And I don't accept misquoting of physics, or misrepresentation of early life vs. end of life physical mechanisms.

And because people have all these unsupported anecdotes about how their speaker changed dramatically changed behavior, despite the fact I have now published about 20 tests over the years where new drivers have negligible break-in, and the changes in F(s) and Q tend to counteract, and are negligible (see Vance Dickason and Andrew Jones for example). It's absurd that people think these very large changes in sound actually occur.

Anecdote:
my first speaker with MSW (Manger Schall Wandler) took a lot of time to be finished, and at first listening sounded worse than a LS3/5 ever would.
Checking the crossover gave no error, cables and polarity were correct ... so I dragged them back into the basement, there polarity reversed and face to face positioned with a blanked over all they were treated by noise over night, and the next day it was at it should be ....
The MSW may be outstanding in this aspect as elasticity is the central point of sound reproduction, but since then I give some time for whatever burnbreakwear-in.
Does cost neither arm nor leg, and if helpfull, helps, if not, does no harm.

And there you go. You acclimated to your speakers. LS3/5A are an acquired taste, I know this. So are Manger. I really think nothing broke in. I am willing to believe that Manger is an exception. But to be honest, I have measured new out of the box literally hundreds if not thousands of drivers from dozens of manufactures in the course of my old job, and remeasured many of them after use for service and the parameters don't change in a way that is audible, especially as you describe.

 

[Salt]

You acclimated to your speakers. LS3/5A are an acquired taste, I know this. So are Manger.

Never (said I was) acclimated to LS3/5, just listened to them 20 or 30 minutes a 30 years ago, not really impressed (morely bored).
And Manger is probably not the only exception, as there may be some more drivers out there need some treatment to give them stable state of parameters.
Don't know what stuff is on YT, but to quote myself: "if done properly" "does no harm".

Peace
(steal this one once, peace)