Auto power setting for sub-woofer

[BCorson]

How does setting the power switch to AUTO on my Boston Acoustics sub-woofer work? It is powered on a SWITCHED outlet on my receiver, so when I turn everything off,I get a loud BUMP!! through my sub as it powers off. This is a beefy sub so the noise it makes will get your attention,it also sounds like it is not good for it. I have a choice on the power switch..OFF AUTO ON.I dont want it to run all the time but I dont know how the AUTO works. Please help, Thanks a Million.

[gary]

auto works by detecting audio signal input and will place the set into standby after a period of time , only down side is if audio is quiet sub may go into standby on its own convinced that the signal has been removed.