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Old 04-10-2009, 10:10 AM   #1
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Must insulate please help!


Hello everyone!

So the spot that I have chosen to install ceiling speakers is pretty much the ideal spot to be equally distance from the other speakers and for the most part, aesthetically pleasing in accordance with the existing recess lighting and the other 5 speakers on the ceiling.

However i have one problem, the left rear speaker, happends to be right next to romex. I'd say there are about 6 romex running perpendicular to the joists through drilled holes. Although I haven't bought speakers yet to try them out, I'm pretty sure that the magnet is most likely to touch one if not two of the romex. my concern is inductance. and is there anyway I can shield some of it away with say a copper mesh screen or whatevers to minimize any inteferrence. Any help would be great....

another option would be to have external wall mounted speakers on the ceiling...but that, i'm hoping is the last solution.
BTW these will not be hardcore THX certified....etc...just good decent speakers that will be good for movies and decent for music.

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Old 04-10-2009, 10:15 AM   #2
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Must insulate please help!


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Originally Posted by genner View Post
Hello everyone!

So the spot that I have chosen to install ceiling speakers is pretty much the ideal spot to be equally distance from the other speakers and for the most part, aesthetically pleasing in accordance with the existing recess lighting and the other 5 speakers on the ceiling.

However i have one problem, the left rear speaker, happends to be right next to romex. I'd say there are about 6 romex running perpendicular to the joists through drilled holes. Although I haven't bought speakers yet to try them out, I'm pretty sure that the magnet is most likely to touch one if not two of the romex. my concern is inductance. and is there anyway I can shield some of it away with say a copper mesh screen or whatevers to minimize any inteferrence. Any help would be great....

another option would be to have external wall mounted speakers on the ceiling...but that, i'm hoping is the last solution.
BTW these will not be hardcore THX certified....etc...just good decent speakers that will be good for movies and decent for music.
The inductance of a straight piece of wire is almost nothing, unless a large amount of current is flowing through it. It is unlikely that any one of the romex near the speaker has a large current at any one time for very long. Most likely the romex power receptacles that have little load on them usually or some lights that don't draw a lot. I wouldn't worry much about it.

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Old 04-10-2009, 10:23 AM   #3
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Must insulate please help!


Yes.
No problem, no 60 Hz hum, no nothing.
Romex puts out an H field, not an E field, so copper [being non-magnetic] won't be of much help.
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Old 04-10-2009, 12:31 PM   #4
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Must insulate please help!


ok well that's much of a big relief.

So supposedly there's not a huge load on the 6 romex's that are running perpendicular along the joists...except for 1. 1 of the 6 romex cables could possibly be powering 5 75-100 watt light bulbs for the recess lights.
If then...would I start hearing a hum?
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Old 04-10-2009, 12:38 PM   #5
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Must insulate please help!


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ok well that's much of a big relief.

So supposedly there's not a huge load on the 6 romex's that are running perpendicular along the joists...except for 1. 1 of the 6 romex cables could possibly be powering 5 75-100 watt light bulbs for the recess lights.
If then...would I start hearing a hum?
Maybe, in a quiet room, with the amplifier on but no sound, and with your ear near the speaker, and if you turn the lights on and off, you may hear a tiny click in the speaker. But I doubt it. So, no.
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Old 04-10-2009, 12:59 PM   #6
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Must insulate please help!


ok well that's good...

ideally what will make it hum loud enough? what type of load are we talking about?

oh and will those clicks travel back to the amp/receiver and damage it in any way?
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Old 04-10-2009, 01:24 PM   #7
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Must insulate please help!


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ok well that's good...

ideally what will make it hum loud enough? what type of load are we talking about?

oh and will those clicks travel back to the amp/receiver and damage it in any way?
Usually hum is introduced by improper grounding at the head end equipment, and by other electronics that can broadcast interference at frequencies higher than the 60 Hz of the power line. Proper spacing, grounding and shielding can eliminate most noise.

In order for the speaker itself to pick up noise, well I guess if the two wires inside the romex were separated (because they cancel each others' field when in close proximity), and one of them was coiled around the speaker for a good length, then you may get a noticeable hum when current was flowing through the power line.
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Old 04-10-2009, 04:13 PM   #8
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Must insulate please help!


Plus the Romex conductors are next to each other, so the current going one way cancels out the field of the current going the other way.
Also, mag. fields weaken very quickly with distance. I think twice as far away gives you only 1/8th of the field strength.

Try it.
Put a speaker next to the cord for a toaster that is on. This is 10A of current. I'd be surprised if you heard anything.

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