boston acoustics subwoofer making awful noise

Are you using a Y splitter? If so, try bypassing that and see what happens. Does the sub have LFE and separate low level (RCA) connections? If it does, try using the connection type opposite of what you're using now. It could also be the connector has some oxidation. Try plugging and unplugging the cable from the sub 4-5 times, twisting it a little each time. If there's some crud on it that might be enough to clean it off. If that does work then it might be a good idea to use some electronic contact cleaner to do the job completely.

More than likely it's the sub though, and not the receiver or cables, so the above may not be all that beneficial.

Do the finger test. Touch the pin on the RCA cable connected to the sub's input. You should hear a buzz. If not, signal is not getting into the sub. Also make sure the sub's gain control is not dirty - wind it up/down a few times.

Since moving the cable used to be a solution and you have tried different cables, I suspect it may be a problem with the socket. Replacing the RCA socket on the sub may or may not be a simple task. All depends on what type it is.

Try a single RCA cable, if it persist, use the other RCA inputs, assuming that it has left and right inputs.

You can also try speaker level inputs to validate that the RCA inputs is the culprit

In a few instances, individuals have moved avrs or subwoofers with the rca cables attached. If they bump something, then the solder holding the rca connection in place may come loose. The connected rca cable causes considerable extra torque. They solve their problem by resoldering the connection.
This is what ransac referred to earlier.