Subwoofer


I noticed my subwoofer with my home theatre setup was not working.  When plugged in, makes a distorted on and off sound.  Replaced it with another sub and worked fine for about a month.  Then it stopped working too.  Has a bad distortion sound almost like its blown.  Any ideas of what this could be.  I hate to buy another sub if it has something to do with the home theater receiver I am using.
hudbar