I've got the Titanic 12 in a 4 cu ft vented box which is great for HT and sometimes good and other times not so good on music. I really believe the recording is more crucial than the box but want to try sealed. What is the best way to close the port temporarily?And what causes those below 40 Hz booms and thuds that obviously aren't a part of the music. Receiver? Plate amp? Stupid recording engineer?