Thiele Small parameters describe the low frequency behavior of a loudspeaker. Cms is the compliance of the suspension of the loudspeaker. Compliance is the inverse of stiffness. So Cms tells you how compliant the suspension of the speaker is....or, by extension, how stiff the suspension is (a higher compliance means lower stiffness, lower compliance means higher stiffness). When a subwoofer "breaks in", the only physical parameter that changes is the compliance of the suspension (Cms). Cms increases (the suspension becomes more compliant) because the suspensions loosens up and becomes softer and less stiff. Since Cms changes, it changes most of the other relevant T/S parameters that predict how a loudspeaker behaves in the low frequency realm. Fs is the resonant frequency of the driver. This is your basic mass on a spring stuff. The mass of the moving parts (cone, coil and former, & suspension) and the "spring" is the suspension, and at some frequency these parts will naturally resonant just the same as any other mass on a spring. That's Fs. And since the compliance of the spring changes, the resonant frequency changes. Fs will go down because there's slightly less "spring" with the same amount of mass, so it resonates at a lower frequency. Q was short hand for Qms, Qes and Qts. Q stands for Quality factor. Basically if a system is resonating, Q describes the amount of "loss" in the system or the amount of damping the system is providing....it tells you how long that system will resonate for. A higher Q means there is less loss (and less damping) so the system will be more resonant and will take longer to stop oscillating. Back to our mass on a spring, Q factor will determine how long it takes for the system to stop oscillating. Qms describes the damping provided by the suspension (surround and spider). Qes describes the damping provided by the motor. And Qts is the combined damping of the Qms and Qes, or the total damping of the driver. Generally speaking the motor provides the most control over the driver at and above resonance, so Qts is always much close to Qes than it is to Qms. There is also Vas, which is more or less a different expression of the compliance of the loudspeaker. It's expressed in terms of air volume, liters or cubic feet. A larger Vas for a given cone diameter means a more compliant (less stiff) suspension. Vas has a lot to do with enclosure volume. Generally speaking, a larger Vas means a larger enclosure volume is needed for a given alignment. Fs, Qts and Vas are the main parameters the describe what the shape of the response curve of a speaker will look like in a given enclosure. Now, Cms is really the only physical parameter that changes when a speaker breaks in. But since Cms changes, Fs and Vas will both change (Fs goes down, Vas goes up). And since Fs changes, Qes and Qms will both change (they go down since Fs goes down) which therefore changes Qts (goes down as well since both Qes and Qms go down). Looking at the math helps understand that part of it. But, more importantly, because Cms is the only physical parameter that changes that means Fs, Vas and Qts will all change in proportion to each other leaving their relative ratios pretty much the same. Which means the shape of the response in a given enclosure remains pretty much the same. There are small changes to the response, but they are are well below the threshold of audibility...less than 1db. It might, *MIGHT* matter to a guy who does SPL where .1db can be the difference between 1st and 2nd place. But audibly....no difference.