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In Reply to: Here's the GR Research data.... posted by jonbee on April 12, 2007 at 12:17:06:
What about measurements after 10 minutes?what about measurements after 1 hour?
what about measurements after 2 hours?
what about measurements after 5 hours?
Given the ridiculous gap between 10 seconds to 20 hours, there's no reason to trust the methodology used for this test
Of course all the measurements are close, so there's no way you could simply look at the numbers and declare exactly what parameter changes would be audible, and what changes would not be audible.
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Richard BassNut Greene
Subjective Audiophile 2007
Follow Ups:
Measurements were taken at 10 seconds because there is a myth that a woofer will have fully burned in within the first few seconds of use. Measured data obviously does not support that myth.I also posted the differences due to temperature changes that occur when the driver is played hard verses after a cool down period. Some were unaware of this.
Having measured drivers at various stages of the burn in process I would compare the changes in the T/S parameters to this illustration.
Take a woofer that has been playing for many years and take the T/S parameters. This represents an end result.
Now take a new driver and measure it.
Play it hard for about a hour. Parameters are now somewhere in the middle, halfway between where they were and where they will end up
Now for each time that you double the amount of time on the driver you can move the parameters to a range that makes them half way towards the fully burned in unit.
Double time again and move half way again...
You eventually get to a point that the next doubling of time is a lot of time and there is a very little change in the parameters.
At some point you have to say that it has reached a settle range and is burned in.
This measured data was only posted to show the change and the time needed for it to occur. It was not meant to prove audible differences.
To most people the audible effects are very apparent. But depending on your system (quality of), your room, your listening habits, and even you (your own hearing), you still may not notice a difference.
Danny Richie
Lets not confuse measured changes in driver parameters with audibility of those changes.The audibility of driver break-in, if not already handled at the factory, is VERY unlikely to last beyond the first hour or two of use unless the driving signal is quite weak and does not stroke the drivers to at least 1/3 XMAX.
I have been building speakers since the 1960's using non-broken in drivers. The worst drivers for break-in have been subwoofer drivers with heavy duty and/or dual spiders. But every time the audible portion of break-in has passed after one LOUD (as LOUD as I could tolerate) bass heavy techno bass or rap song lasting perhaps three minutes. Break-in could have been complete in ten seconds, but I did not come back into the room until the "song" was over.
The epoxy/chemicals on the driver's spider will 'micro-crack' in ten seconds with a long enough driver stroke -- and that could be accomplished in ten seconds during quality control testing at the factory, perhaps using a sine wave tone at the driver's resonant frequency of sufficient strength to push the cone to XMAX, or better yet, to the rated XMECH.
That peoiple claim to hear break-in for 100 continuous hours of use, which could take months, is a silly belief for ordinary cone drivers.
Of course audiophiles have many beliefs.
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Richard BassNut Greene
Subjective Audiophile 2007
The measured data shows the break in period takes considerable longer than a few seconds. The measured data that I posted is also consistent with similar tests made by other industry professionals.The audibility of the changes absolutely do not settle in a few seconds. Most audible changes are consistent with mechanical parameter changes and need a similar amount of time.
Bass nut> " The epoxy/chemicals on the driver's spider will 'micro-crack' in ten seconds with a long enough driver stroke -- and that could be accomplished in ten seconds during quality control testing at the factory,"
The measured data does not support that assumption.
Danny Richie
including the results from other designers. There are other published findings that are totally consistent. Or maybe you just are happier being a troll, regardless of what others who are far more knowledgeable and experienced than you demonstrate?
I can't find anything in the report that equates the mechanical measurements with actual changes in sound. My apologies if I've overlooked this. The numbers presented mean very little to me in the context of this discussion.The report also mentions that the greatest contributor to speaker burn in is from the electrical burn in, the majority of which is from the burn in of capacitors.
So given this report, my question would be how long does it take a capacitor to burn in?
and the xovers are designed around optimal driver parameters. If those params are different because the driver is new, the xovers won't work as designed, which will certainly affect the sound.
I'll try to explain what I think happens, and how it affects the sound. I'll limit my remarks to the measured driver params listed, not the electronic components that Danny mentions, as those changes are harder to measure.
The fs of a driver is related to its lower frequency limit. If a driver is driven below its fs, distortion rises very rapidly with declining frequency. A higher fs in a new also means that there will be a reduction in the LF output of the driver, and at a given frequency below the fs, there will be higher distortion.
The xovers are designed to deliver energy in a defined and fixed band, with usually a fairly shallow rollof at the ends of the band. With a new driver, with a higher fs the lower part of the xover band will be feeding more energy below the fs of the new driver that xover section is feeding. That means higher distortion at the bottom of the driver's range. As the driver fs drops with use, more and more of the xover band will cover the (expanding) driver's sweet spot.If it is a woofer, this will change the balance of the whole system, making it subjectively brighter overall, with constricted bass. The bass will also exhibit higher distortion, as more power is going to it below its (temporary) higher fs.
For mids and tweeters with high pass filters, the effects are the same, but of course they manifest themselves at the low end of the mid or tweeter range, as aberrations in the lower midrange and low to mid treble.Xover design theory hasn't changed substantially in decades. Xovers are designed around driver params so that each driver is operating in its sweet spot. If the driver params shift, that driver sweet spot will shift as well.
There is no magic or fuzzy thinking at work here, just the application of loudspeaker engineering basics.
I can dig all of that, but it still tells me nothing about how truly audible the changes are in a normal listening environment.
nt
To that end, for the sake of this discussion, the report is rather meaningless.
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