I have seen many websites giving you the formula for port dimensions based on a given tuning frequency, but what I want is something to tell me the frequency based on port dimensions, namely 3" diam x 6.5" port in a 23.4"x8.56"x14.24" (1.65cu ft) box. Thats the recommended dimensions my 12" sub spec sheet gave me but they didn't say what frequency that will end up at...