Burn-In Myth
Woofer Burn-In Testing Overview
First, we would like to extend our thanks to Speaker City and Madisound for promptly supplying a sampling of woofers for this series of tests.
The following woofers were evaluated:
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Dayton Euro Woofer (295-350)
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Seas CA18RNX
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Peerless P832513
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Peerless 830875
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Peerless 830860
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GR Research M-165X
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GR Research M-130
All woofers were new and tested fresh out of the box to the best of our knowledge, with one exception. The M-130 unit was removed from an A/V-1 loudspeaker that had accumulated approximately 200 hours of playback and was used as a control sample. While new units were requested, it cannot be guaranteed that every driver supplied had never been previously operated.
Each woofer was measured under identical conditions using a Clio 7.1 measurement system.
Test Methodology
A 40 Hz sine wave was applied to all woofers simultaneously at a level sufficient to drive each unit to approximately half of its rated Xmax. After each playback interval, the drivers were allowed to cool for roughly two hours to return to room temperature before further measurements were taken.
Measurements were conducted at the following intervals:
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Fresh out of the box
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After 1 minute of operation
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After 5 minutes
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After 1 hour
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After 10 hours
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After 20 hours
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After 40 hours
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After 80 hours
Driving the woofers with a continuous 40 Hz sine wave represents a more demanding condition than typical music playback and therefore accelerates the break-in process. Under normal listening conditions, similar compliance changes may take longer to occur.
Addressing Common Burn-In Myths
This testing was designed to examine several frequently discussed claims:
1) “Speakers do not break in — only the listener’s ears adjust.”
Objective measurements show that suspension compliance changes as a woofer is exercised over time. While these data do not directly quantify perceived sonic differences, they clearly demonstrate that measurable mechanical changes occur.
2) “Any break-in occurs within the first few seconds of operation.”
The results indicate that compliance continues to evolve with extended play time, well beyond the initial moments of use.
3) “Compliance changes quickly recover once playback stops.”
Because the drivers were allowed to cool for several hours between measurements, it was possible to observe that parameters did not revert to their original values.
4) “Drivers that change parameters over time are defective.”
All drivers tested exhibited some degree of suspension softening with use. The magnitude of change varied between models but was consistently present.
Observed Parameter Trends
To simplify the presentation of results, only the most relevant Thiele/Small parameters are summarized: Fs, Vas, and Qts.
During the break-in process:
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Fs (resonant frequency) generally decreased
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Vas (equivalent compliance volume) increased
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Qts (total Q) decreased
Vas measurements showed some short-term variability but trended upward overall.
Temperature Considerations
Ambient temperature can significantly influence driver measurements. Most woofers were allowed to acclimate in the measurement room for several days prior to testing.
The previously used M-130 control driver had been stored in a slightly cooler environment and therefore showed somewhat greater variation than expected during early measurements.
Similarly, the M-165X unit was measured shortly after being removed from a colder storage area. Lower temperatures tend to increase measured Fs and Qts while reducing Vas, which contributed to larger initial parameter shifts compared with other drivers.
I have no data on two of the Peerless drivers from when they were fresh out of the box. This is because later recorded data was accidentally saved in the same file folder under the same name. So the later recorded data saved over the initial data (replacing it). After the driver had time on it then it was impossible to get a new measurement on it when it was fresh. Sorry about that.
