The other day my Beolab 11 started a large humming noise. I have been using it for about 2 years, was purchased used. I had it connected via the in/out pl ports on a beolab 6000 I use as the center. All other beolabs (2x 8000’s L/R and 3x 6000’s C/RL/RR) are connected via custom cables to pre-outs on a denon receiver, and a relay to provide 5v to toggle the power. All others are unaffected, so I think its something specific to the sub.
Google is showing some results on the archive site, but it appears to be down.