turn off your components (midbass, midrange, tweeter) and just play your subwoofer.
I highly doubt you will be able to notice a difference in speed among the woofers.
What you may notice is slight dips and peaks in the frequency response, which you might equate to making the woofer either *slow* or *fast* which is not the case. This is simply solved by adding a parametric equalizer.
If your frequency response is ruler flat...and you still think your woofer is slow than it is most likely the integration with your midrange speaker that is the problem. Work on your crossover slopes and points and im sure you will be a happier man.