@geof3 Spot on! "Constant surveillance", "firm NO".
Worked for me, with two boys, up to a point: during a house move (we'd been there 16 years) we packed up my B&W 801M2s. As one of the speakers was wrapped up by the movers, a Titleist DT golf ball rolled out of the port. It had neither improved nor worsened the bass response. Its presence was inaudible which says something about the Matrix structure. Nobody knows how long it had been in there, I reckon at least 10 years... 😄