[rfeenstra]

The resonant frequency is the frequency that the cone will want to vibrate at most easily. All speakers have a resonant frequency . it would have to be determined experimentally. The patent gives the desired/designed frequency. It would be interesting to compare actual "aged" frequency with original designed frequency. If the current resonant frequency is far away from the original, it may explain why some have said they are not very effective at reducing the boominess of the cabinet.