I just modeled that JL sub in Bass Box Pro and it really isn't the best subwoofer for a ported box and is best in a sealed box. For a Qtc of 7.07, it wants a box that is 3.86 cu ft sealed with an F3 of 37.5 Hz. You should try sealing off that port since the box you have now is close to that size and see how it sounds. You might actually like it. I modeled it ported and let the program dictate the size and it came up with a whopping 8 cu ft with an fb of 19.5. Not exactly what you need!
I modeled the JL recommended ported enclosure and its ok but look how the 3.75 vb sealed compares to the JL ported vb 2.75.With cabin gain the sealed should sound a lot better in this instance.
Link to picture showing ported vs sealed.
https://imgur.com/a/BZZIV6G