@grislybutter When you say “terrible,” what specifically do you mean? It’s possible you’ve got the volume and/or crossover set too high and/or placed in a bad spot. Here’s a quick n easy guide to help at least get the sub’s settings properly dialed in.
https://lifehacker.com/how-to-properly-set-your-subwoofers-volume-without-sh-1506136549
But before doing that I’d do the “sub crawl” method so you can to identify optimal placement areas for the sub in your room. Basically you place the sub on the listening chair where you’ll do your listening, put on a bass-heavy track, and then crawl around your room (so your ears are at the same level as the sub) and identify the place(s) where the bass sounds best (tightest,well-integrated/balanced, tuneful) and mark them with tape. Choose the spot that works best for you in the room and then calibrate the sub’s settings as per the instructions in the above link. If you do this and the sub still doesn’t sound good I’d be concerned there may be something wrong going on with the sub. Last, SVS has excellent customer support and I wouldn’t hesitate to call them if all else fails. Hope this helps — now, on your knees boy!