Break-in for woofers in general is considered as 20 hours of music program at 1/3 of the maximum RMS rating of the speaker. After that it is considered broken in. Very minor changes will still occur after this up to about 100 hours of use, where after no further changes are measurable. By breaking the speaker in over time like this assures that all parts of the suspension stretches equally which will give you long linear travel and optimum lifespan of the woofer.