On Fri, 30 Jul 2010 15:01:33 -0700, William Sommerwerck wrote:

Meanwhile I will take the speaker out and report back if/when I have a
result

But you've already subbed the speaker and the hiss went away or so I
thought I had previously read.

And no one here is aware of a "mechanism" that causes speakers to
produce hissing sounds on their own, especially when you say the sound
is not related to the program material or its volume.

Especially if it is just a passive enclosure. Now a woofer with a built
in amp is an entirely different story.