Hi not sure if anyone can help i brought a Cambridge Audio Azur 351R about 4 months ago but i notice that when ever someone on a TV programme or film with a low voice spoke it hummed on the subwoofer a split second before each word, i have played with the crossover and AV level dials numerous times to no avail. I have ended up turning off the unit now as it has become annoying. Is this a easy problem to solve? (the speaker set is a first generation QAcoustics 5.1)