I can’t return the sub because I bought it from the original owner who also bought and didn’t use it. Also don’t have the box.
Call SVS and see if they have a seller/buyer warranty transfer policy. You need the serial number. Power Sound Audio has a seller/buyer warranty transfer policy that’s good for up to 5 years. And SVS has their own policies too and you may be able to return or trade up for one that suits your needs. Wouldn’t hurt to try.
If you can’t return it to SVS, I think they also sell the boxes for their subs for shipping, as this scenario happens all the time and then you can re-sell to anywhere.