Another question: what do you have the crossover set at? A low setting and a high level setting would make it come in rather abruptly.
Good job sealing the port, and being considerate of others. Since cabinet pressures peak at resonance, leaks around the port will make all sorts of noise.
Try your frequency test again tomorrow (set the x-over above 100 hz to get it out of the picture). As you decrease the signal frequency the cone motion will increase, but at some point it will drop off to a minimum, then go waaay up at frequencies below that. That point of minimum motion will be the cabinet tuning frequency, and it will give us a hint as to how long the port needs to be, and where to set the filter for best performance. That point of lowest motion will also have the highest air velocities in the port, so noise problems should peak there.
These are predictions for the latest info. I will recheck my numbers tomorrow just to be sure (don't trust myself this late). These should be output, excursion, and port velocity. You can see where the excursion limit is exceeded where the color changes from red to, uh, darker red. Sorry about that.