Hello,
Thank you for your comments and I did tried all suggestions posted here. I did return the original sub after one week and got a new replacement one, but same issue with port noise. Here is my system spec so hopefully my setup is correct:
- Harman Kardon AVR-144 receiver.
- JBL N38 front L/R (older model, not the N38 II)
- JBL N28 rear surround (L/R) (not the II model).
- JBL SC-305 center.
- Sub connected to AVR to LFE using heavy shield cable.
- All speakers set to small; Xover of all speaker at 80Hz; 0db power setting in the avr for all speakers.
- Grain/power at 10 o'clock on the sub (around 1/3 power). Cross over all the way on the sub.
- Only watch movie/listen to music at -30db to -25db power level on the receiver.
The room size is about 12 feet x 18 feet in the basement and at 1/3 power is more than enough for movie/audio. I just need nice clean but not looking for floor shaking bass. Most of the time I use my HT/man-cave is after my son (12 years old) went to bed - hence don't want to wake him up. I did check to make sure no air leak, block port,...... and definitely the noise caused by heavy air pushing out of the port at a certain bass frequency.
Right now when watching movie, I would turn the sub volume at 10 o'clock position, set all speaker to small. But when listen to music, I would turn the sub volume down to at 9 o'clock position and set my front speakers to large. That would help a lot with port noise but quite a bit of inconvenience of changing settings for movie or music.
If I do a bass frequency check to see when port noise is as per a suggestion here, then what is the next step to minimize port noise at that certain frequency? Also I am thinking of stuffing the port with drinking straws and see if it would help --> but then would decrease the sound output of the sub.