[archimonde]

Hi,
 
I don't know is that a issue but yesterday when computer playing music i turn off my av40. 
And they give strange low frequency noise. Is that makes any problem?
 
thanks.

 

[euphoracle]

Mine pop when they are turned off.  Probably some dodge capacitors.  I'm replacing them at some point soon, though.

 

[mrnoodle]

It's probably coming from speaker magnets responding to clicking of switching relay, common to speakers and audio equipments.
My PC speakers and bookshelf audio system have been making this pop noise for years when turning off.
Some devices do implement anti-pop circuitry but nothing to worry about, nonetheless.