Most rooms have very uneven bass response, so if you tune things to sound good at say, 60hz, and you happen to have a 12db bump at that frequency, your ultra-low frequencies might be 15db low.
I originally had an OLD Velodyne. I bought a used Velodyne SMS-1 to EQ the subwoofer, and it made a tremendous difference.
Now I have an SVS-SB16 Ultra. It has 3 completely customizable EQ points, so everything is done in the sub.
Unfortunately, they don't have a low pass output, so my main speakers have to run full range, making the overlap significant. The EQ helps a lot with that though.
I think the SB13-Ultra might have low-pass AND EQ, but I can't swear to that.
If you decide to get something like the Velodyne SMS-1, note that it will add more group delay. That may or may not be an issue for you. I still use my SMS-1 to measure the results of my EQ tweaking in the SB-16. It's a handy gizmo.
I originally had an OLD Velodyne. I bought a used Velodyne SMS-1 to EQ the subwoofer, and it made a tremendous difference.
Now I have an SVS-SB16 Ultra. It has 3 completely customizable EQ points, so everything is done in the sub.
Unfortunately, they don't have a low pass output, so my main speakers have to run full range, making the overlap significant. The EQ helps a lot with that though.
I think the SB13-Ultra might have low-pass AND EQ, but I can't swear to that.
If you decide to get something like the Velodyne SMS-1, note that it will add more group delay. That may or may not be an issue for you. I still use my SMS-1 to measure the results of my EQ tweaking in the SB-16. It's a handy gizmo.