Just out of curiousity, what kind of volume levels are you using?
The buzz in my 2 (out of 4) woofers never appeared until i had the volume at the 'party' level. A lower, typical easy listening volume produced no buzz but again as i mentioned earlier, the higher volumes i was using should still be well within the capability range of both the speaker and the receiver.
Hopefully the 2 woofer replacements will arrive today.

"Those who preach the myths of audio are ignorant of truth."