I've just replaced my 309W sub with a 909W to get a bit of extra oomph with my Avant 900 setup. Unfortunately I get a loud humming noise from the unit when its connected to the amp, irrespective of whether the notch filter is on or off. The 909W is connected to the same power point, with the same sub cable as the 309W which had no humming at all. Hence there should be no issues with the Amp, leads etc. Do you think its a faulty Sub? Tons, is MS aware of humming issues with the 909s?