Even unknown is if interference is via radio waves (over the air),
from cable, or via AC power lines. Will a ferrite bead do anything?
Not for lower frequency noise. Meanwhile, what do you put that ferrite
bead on? Ac electric? Cable? Speaker wires? Or maybe combinations?
Just another example of why shotgun solutions rarely are useful or may
only cure symptoms.

Your first efforts are to find what is and is not reason for problem.
How is the house wired? What connects to that AC mains circuit. What
is the connection relationship between things woofers and 'interfered
with' appliance? For example, that other TV farther away may actually
be electrically closer. You don't know until household wiring is first
defined.

Meanwhile, you are entertaining myths if you think a surge protector
does anything for this. Furthermore, what is this 'line
conditioner'? To be effective, it is how many tens of pounds? Why?
Any smaller 'conditioning' must already be part of the appliance.

Don't entertain myths. Don't change anything with intent to fix it.
Currently, your only concern is to identify symptoms. Solutions come
later. What does and does not change anything? How and how much?
What share same branch circuit and what are not on same AC phase? Of
course, we assume this is post 1960s wiring where safety grounds exist
in all receptacles. Which appliances are two prong or three prong AC
plugs? We must assume because important facts are not yet provided.

For example, what happens when the 'interfered' operates only from a
battery backup UPS without any connection to AC mains. Just another
essential fact to start estimating where interference is coming from.
Note the word estimate - not 'know'.

Another useful testing tool may be:
http://www.schurterinc.com/products/usa/pemfilter.asp
http://www.corcom.com/
http://www.cor.com/PDF/Q.pdf
http://www.interpower.com/ic/p30-35list.asp

http://www.interpower.com/scripts/ws...nly_filter=YES

EMC/EMI is an art. Problems can be so complex that conferences of
these industry professionals consist of mostly balding participants.
Your hope for a useful reply is based in information you provide
because useful answers involve that much grasp of technology.

Meanwhile, get rid of the myths. That surge protector does nothing.
What is this 'line conditioner'? Where is this 'ground' that will
somehow eliminate radio frequency noise? The ferrite bead goes where
and does what? What appliances are (may be) missing required filters
(to sell at discounted prices)?

More useful information. What creates interference to an adjacent AM
radio when not tuned to any strong station? If you have that noise,
now you have a tool to trace where that noise does and does not exist.

Do incandescent bulbs dim or brighten when larger appliances start or
stop?

wrote:
Anytime my subwoofer draws a lot of power (or any large appliance in
the house..ie washer\dryer), white dotted lines appear on the TV.
When the subwoofer uses high power during loud scenes, the condition
gets worse showing more pronounced interference lines. I read that
cable grounding could be the issue. But, I disconnected my cable from
the TV...so that only the DVD player is connected. But, I'm still
noticing the problem. Even the TV in the back room shows the
interference lines (to a lesser degree). I've connected the subwoofer
and all my components to a/v surge protectors with line conditioning,
but that doesn't help. Any ideas on how to fix the issue?