I have a similar setup.
You have to get the sub blended properly with the mains and all those adjustments are your tools. First level but then also rolloff frequency and then phase.
The trick with one sub is get that all right at your listening position because bass levels will vary within the room no matter how you adjust a single sub.
Try getting it right at the sub location first where you can make fine adjustments fast and easy as needed and get familiar with how the controls affect the sound.
Then take what you’ve learned and listen from you main listening position and make the adjustments for that until right.
Leaving ports open will extend the low frequencies of the mains and allow the sub to come in at a somewhat lower frequency that is less directional and less likely to call attention to a single subs location in the room.
Also helps to know at what frequencies your mains and sub roll off to help determine the rolloff frequency range to shoot for when adjusting that on the sub.
In general, the larger and more extended the mains, the larger and more extended the sub will need to be to fill in the low end missing otherwise rather than just boosting existing bass levels which is generally not what you want.
Also remember that bass levels and sound will vary largely from recording to recording. Use a good quality track or two or three with lots of good extended bass as your reference tracks and adjust for those so that bass is good but not overwhelming. Then see how that works but do not expect great bass from all or even most recordings else you will be tuning forever.
You have to get the sub blended properly with the mains and all those adjustments are your tools. First level but then also rolloff frequency and then phase.
The trick with one sub is get that all right at your listening position because bass levels will vary within the room no matter how you adjust a single sub.
Try getting it right at the sub location first where you can make fine adjustments fast and easy as needed and get familiar with how the controls affect the sound.
Then take what you’ve learned and listen from you main listening position and make the adjustments for that until right.
Leaving ports open will extend the low frequencies of the mains and allow the sub to come in at a somewhat lower frequency that is less directional and less likely to call attention to a single subs location in the room.
Also helps to know at what frequencies your mains and sub roll off to help determine the rolloff frequency range to shoot for when adjusting that on the sub.
In general, the larger and more extended the mains, the larger and more extended the sub will need to be to fill in the low end missing otherwise rather than just boosting existing bass levels which is generally not what you want.
Also remember that bass levels and sound will vary largely from recording to recording. Use a good quality track or two or three with lots of good extended bass as your reference tracks and adjust for those so that bass is good but not overwhelming. Then see how that works but do not expect great bass from all or even most recordings else you will be tuning forever.