SA-HT700 Panasonic

[spartacus]

A friend of mine has SA-HT700 Panasonic. When she tries to use her Home Theatre either to watch movies or tv, as soon as the sub woofer goes on she gets bleed through of an am radio station through her woofer loud enough to be very annoying. Everything runs through the woofer so as soon as the receiver is turned on the woofer comes on and so do the speakers. I looked and noticed that whoever set up the speaker wires did use monster cable but also a cheaper cable. Is that what is causing it? Its also running behing the wall so maybe its hitting pipes or something? Cannot find much info on this home theatre on line. I guess its not a top of the line but never the less for a couple of hundred it would be nice to use the system without Sister Mary preaching the gospel during movies. Any suggestions? thanks<BR><BR>

[asw_tech]

Greetings sparticus, welcome to the forum. Lets look at a couple simple things first.<BR>You mentioned everything is hooked thru the subwoofer. Is that including the main L&R speaker outputs? Is there any way to use an LFE coax instead for this setup? Or doesn''t this receiver have bass mgt? If not, then it maight be necessary to try installing loops in the wire between the receiver & the subwoofer.<BR><BR>I know this sounds awful and looks as bad, but what you may have going on is the speaker wire behaving like an antenna. In order to break down the signal interferring with subwoofer. (try looping 1 channel between the receiver & the sub) See if that channel''s noise clears up.<BR><BR>Also a cheap fix is to use a gnd buster (3 way to 2 way)adapter plug, insures you aren''t using the water pipes as an antenna and feeding religous radio to your stereo (involuntarily) I''d try this fix first as it''s easier and not very expensive.<BR><BR><BR>Also do you have a power strip with ac filter like a triplite isobar or monster power bar? If so, make sure the receiver & the subwoofer are plugged into the line isolator.

[spartacus]

Thanks for the info. I have tried your suggestions. Here is what i found. The line already had loops in it, but i added more and also made sure to tape the speakers wires to the wall to keep away from any pipes or aluminum framing. I then used the surge protector and that ground adapter and the am bleed was still there. Speaker wires are monster cable so they are pretty good. I unplugged each set one at a time and checked to make sure they were setup properly, pos to pos, neg to neg etc. When i unplugged one of the rear speakers the woofer got much much quieter. The am bleed was very faint, only noticeable when sound was off and ear up to woofer. Then when i unplugged the cable from the back of the offending rear speaked the sound got loud again. Weird that both ends are unplugged and the bleed is loud. So i plugged some old cheap speaker wire into the woofer and then the other end into the speaker and the sound was again very faint. Weird that the monster cable would cause the bleed but not the cheap wire? NOt sure where to go from here. Should I just use another set of speaker wire for the rear speaker?

[spartacus]

So no one has anymore suggestions for me?<BR><BR>thanks

[asw_tech]

you might want to try this as a last resort. We used to do it to avert war with the Cber's in the old days. Shield the wire going to your woofer. Perhaps try using long thin strips of alum foil? The loops concept came from similiar cause & effect.<BR><BR>The only other thing I could think at this time, is trying a different a/c circuit for your sub. Poorly shielded outlet might be culpable here. If you knew anybody who worked for a radio station it might help.<BR><BR>They use test equipment which allows you to pinpoint the source of noise (EMI) and isolate it. Similiar to a mic & test set, only it's not acoustical.<BR><BR>In the end, if the cheaper wire helps alleviate it some, then I'd go with it. It's not very scientific, but perhaps the monster wire (length) might have something to do with it? Longwire antennas resonate at different lengths depending on the wavelength you're receiving, or in this case trying not to receive! AM band 530 - 1600 khz or (.6 - 1.6mhz) which translates into a very short length. Less than 2 feet and you got an antenna!<BR><BR>Changing the length of wire might help mediate some of that stray rf interference. Also if your near any powerlines, the low levels of emi they create could be causing you probs too. Perhaps aluminum blinds might help? If you have aluminum blinds, try opening them. Basically you're trying to change the rf patterns in that room for least amount of noise.<BR><BR>Once you grasp that, you begin to see things in RF terms, not just a physical sense.<BR><BR>Ferrite noise blocks might help too? Or do some reading up on the subject?<BR><BR>http://www.arrl.org/tis/info/rfi-elec.html<BR><BR>http://www.arrl.org/tis/info/rfiaudio.html<BR><BR>Good luck!'/idealbb/images/smilies/2.gif'