Sealed box calculator

How a sealed box works

A sealed (acoustic-suspension) box adds the stiffness of the trapped air to the driver's own suspension. That raises the total system Q from the driver's Qts to the in-box Qtc, and the resonance from Fs to Fc. A smaller box means a higher Qtc and Fc (punchier, but with a peak if too high); a larger box lowers both toward the driver's free-air values.

A Qtc of 0.707 gives a maximally flat (Butterworth) response with the lowest F3 for a flat curve; 0.5 is a critically damped transient-optimum; many builders pick 0.7–0.8 for a good balance. To model the full response, impedance and excursion of the finished box, use the enclosure designer.