My Sunfire use to do that until I had Bill F rebuild it and adjust the threshold to a lower level. Cost about $260, so you might want to consider a new subwoofer. Best wishes
Subwoofer
Can anyone if possible answer why my subwoofer goes into stand by mode all the time after just a few minutes of playing if the song is base heavy its ok movies are better in paticular new films but i find myself always adjusting the gain up and down its a Sunfire True Subwoofer MK IV have mains center and rears set at 90 hz as the sub as well should i open the hz on the sub all the way but it gets to boomy i like tight tight bass at lowest db.I know this is a hard question to answer is it possible the sub itself is just getting old using old Sony ES 9000 for pre/pro. Thanx for the rookie question.😀.