This is going to sound very weird, but is this little niggle is driving me barmy. When I play dvd's on my Wharfedale 750s through the tv speakers there is , what i can only describe as slight rumbling noise underneath the dialogue track. It's driving me crazy trying to work out what it is!! It only seems to be with dvd's although i did hear it the other day while channel hopping and watching 5 minutes of Babylon 5??!!