i'm using the 970/7075 combo. i'm thinking the buzzing is either something on my av rack which is rattling which i can seem to find, the speaker not being able to handle the bass, or the idea of the sub firing into the corner area of the room. the buzzing is rather faint. you can only notice it when the volume is up, bass is up, and you are a few feet from the speaker. any ideas? i can not take the powered sub out because it is built into the 533-PT and the woofer is the side firing sub.