You can set a BFD filter at 20Hz, use a relatively wide BW and tame that peak if you want to. Some folks would leave it alone to compensate for the ear's drop in sensitivity.
For the hum, if it is a ground loop between your receiver and the sub, a cheater plug may be the only option.
Is the sub on the same 120V leg of the house power box? If not, try another outlet for the sub that is. (This is not likely the solution, but it is worth a try).
Have you checked the routing of the cable from the output of the receiver to the sub? It does not take much of a parallel run to an AC cord to cause hum. If the sub cable has to cross AC cables, arrange them so that it crosses at right angles.
For the hum, if it is a ground loop between your receiver and the sub, a cheater plug may be the only option.
Is the sub on the same 120V leg of the house power box? If not, try another outlet for the sub that is. (This is not likely the solution, but it is worth a try).
Have you checked the routing of the cable from the output of the receiver to the sub? It does not take much of a parallel run to an AC cord to cause hum. If the sub cable has to cross AC cables, arrange them so that it crosses at right angles.
