its really cool there are two tuning frequencies the internal and external...the external tuning is always 15% lower then the internal so in my case its 31 and 26....the woofer plays as if it is in a normal 31hz tuned box until you get to the frequency at which the driver starts to unload at which point it unloads into the second chamber and combines with the second port to form the lower tuning point so you get the response of a box tuned to 31 as well as a box tuned to 26 which is essentially not really need but cool as shit anyway