1) Speakers don't burn in its your ears that burn in.
Obviously, as a woofer is played over a given time period the suspension compliance changes. This objective data showing changes in the T/S parameters as the suspension loosens up does not prove noted subjective differences in the perceived output, or how a speaker sounds, but does prove that there is something more taking place than getting used to the sound.
2) What break in does occur in a driver occurs within the first few seconds of opperation.
Clearly changes in a drivers compliance continues to change with extended play time well in excess of the first few seconds of play.
3) Within just a few minutes of the stimulus being turned off, most if not all of the change in compliance will completely recover and the parameters will reverts back to the original specifications.
Since the drivers were allowed to cool for several hours between taking the measurements we can clearly see that at no time did they revert back to previous measurements.
4) Drivers whose parameters change over time are defective.
All drivers will show a softening of the suspension when played over a given time period. Some will change more than others.
Below is a summary of the changes in driver compliance during the burn in process. Changes can be seen in Fs, Vas, and Qts parameters so those are all that are shown to minimize redundancy.
There are several things to note. As a woofer goes through the burn in process the Fs will drop, Vas parameters will increase, and Qts parameters will decrease. Vas will tend to have a small amount of variance between measurements and will bounce around a little in some cases but it will generally and always increase in value.
Temperature can and will effect these measurements. All drivers shipped in had set in the measurement room for several days to adjust to room temperature with a couple of exceptions.
The already burned in M-130 woofer that was removed from an A/V-1 speaker was stored in an area that was slightly colder than the measuring room. Even though it showed less change to from the burn in period than other drivers since it already had time on it, it had showed more change than it might have since it was not allowed enough time to completely warm up to room temperature.
The M-165X woofer was fresh out of the box that was from our storage area. It was quite a bit colder than the temperature in the measuring room and caused the greatest amount of change in initial measurements compared to the other drivers. The colder temperature causes the Fs to be higher, Vas to be lower, and Qts to be higher.
