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 Post subject: How Can I Silence My....Speakers?
PostPosted: Sun Jan 24, 2010 9:29 am 
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I have a set of Creative Inspire P7800 7.1 speakers. They are great for the money ($80 when I bought them a couple years ago). However, they are very susceptible to interference from EMF-generating devices such as cell phones. When it was only a problem with cell phones, it was not so bad as the problem only presented itself if the phones were near the speakers or if someone in the room was on the phone.

Now I've had to replace my router because it was failing; the new router is a great Cisco router with VPN and Draft-N wireless w/multiple isolated SSID's. Unfortunately if I enable the wireless, the interference with the speakers is CONSTANT.

I am wondering what it would take for me to insulate the speakers from this interference? Any ideas?


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PostPosted: Sun Jan 24, 2010 12:41 pm 
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Another possibility:

The electromagnetic interference might be picked up by the audio circuitry at the microphone inputs and then amplified out to the speakers.

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 Post subject: Re: How Can I Silence My....Speakers?
PostPosted: Mon Jan 25, 2010 3:19 am 
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Fëanor wrote:
I am wondering what it would take for me to insulate the speakers from this interference? Any ideas?

Probably shielded wires?


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PostPosted: Mon Jan 25, 2010 7:11 am 
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It's probably actually the insides of the speakers that are lacking shielding, rather than the wires.


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PostPosted: Mon Jan 25, 2010 8:10 am 
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If it does that to speakers, I worry what it does to our brains...



Now where did I put my tinfoil hat?


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PostPosted: Mon Jan 25, 2010 9:03 am 
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I have the same problem with my 2.1 Empire R401 speakers (wooden speakers and subwoofer), and I believe the shieldless wires are the problem.
But I couldn't find audio quality shielded wires, the ones I have are black & red. I suppose I could use TV coaxial cable instead? Or some other kind of shielded cable?
If you people know where to find audio quality shielded wires, please post a link here.

PS. Would this be OK? http://www.amazon.com/Channel-Spiral-Sh ... 180&sr=8-8


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 Post subject:
PostPosted: Mon Jan 25, 2010 1:37 pm 
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swivelguy2 wrote:
It's probably actually the insides of the speakers that are lacking shielding, rather than the wires.

Well, that is easily tested - if the cables can be easily rerouted/moved. My money is on the cables ;)
*idea*
But the OP did check the sources, right? I know that e.g. my cellphone does interfere with my tuner if I get too close...

Tzupy wrote:
I have the same problem with my 2.1 Empire R401 speakers (wooden speakers and subwoofer), and I believe the shieldless wires are the problem.
But I couldn't find audio quality shielded wires, the ones I have are black & red. I suppose I could use TV coaxial cable instead? Or some other kind of shielded cable?
If you people know where to find audio quality shielded wires, please post a link here.

PS. Would this be OK? http://www.amazon.com/Channel-Spiral-Sh ... 180&sr=8-8

Are those speakers passive or active? Google returns a lot of languages I do not understand... If they are active you could use coax cables, for passive ones the diameter of coax cables is a bit small.
The link you provided does not mention the diameter/core material of the cable - could be anything.


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PostPosted: Mon Jan 25, 2010 2:46 pm 
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It is likely that the interference is happening at the subwoofer amplification circuits. You could try moving the subwoofer across the room and see if that helps.


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PostPosted: Mon Jan 25, 2010 5:04 pm 
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The anti-static bags that PC parts come in is actually pretty good at blocking these kinds of interference.

You can try to put some bags between the speaker and the router and see if that helps. Not the prettiest solution, but it should work.

For bigger bags, usually video cards come in big bags.


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PostPosted: Tue Jan 26, 2010 5:50 am 
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My speakers are 8W each and the subwoofer 30W RMS power, so a total 46W. I believe the speakers are passive, since they are fed with only 2 wires.
The speakers are magnetically shielded and have '3.5" mid-range and 1" tweeter', the subwoofer has an 'inverse phase hole 6.5" driver'.
The PC connection is a jack, splits into a 2 channel RCA and goes into the subwoofer case (these wires also don't seem shielded).
From the subwoofer each speaker receives the signal through a pair of black / red wires with NO connectors at their ends, they're just clamped to make contact.


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 Post subject:
PostPosted: Tue Jan 26, 2010 9:57 am 
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What's your PC case? Is it properly enclosed? Maybe the interference takes place at the source.

If you have a laptop handy, test feeding your speakers off it instead.


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 Post subject:
PostPosted: Tue Jan 26, 2010 2:19 pm 
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Tzupy wrote:
My speakers are 8W each and the subwoofer 30W RMS power, so a total 46W. I believe the speakers are passive, since they are fed with only 2 wires.
The speakers are magnetically shielded and have '3.5" mid-range and 1" tweeter', the subwoofer has an 'inverse phase hole 6.5" driver'.
From the subwoofer each speaker receives the signal through a pair of black / red wires with NO connectors at their ends, they're just clamped to make contact.

Yeah, that means they are passive. And with 8 W you can probably run them from coax without a problem.
But as mentioned, check your sources first. Best way to do that is imhO with a MP3 player.


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 Post subject:
PostPosted: Fri Jan 29, 2010 2:15 am 
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First of all, I apologize for hijacking this thread from the OP, this wasn't my intention.
Second, my problem isn't permanent, I haven't a wireless router, and I won't get one if I have a choice.
The interference is with the mobile phone, a cheap Samsung that I use for local calls. And sometimes with a radio station.
I also have an iPhone (for international calls), but it doesn't cause this kind of problem.
The PC case is Solo / P150 (I have two PCs) and it's intact, no case maiming here. Case fans are Slipstreams at ~700 rpm.
I tested with a Sony laptop and the problem with the interference speakers / mobile phone is the same.

I ordered quality shielded cables, jack to RCA and two stereo RCA cables, I hope they will solve my problem.


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 Post subject:
PostPosted: Fri Jan 29, 2010 3:28 am 
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I don't think the interference happens in the cables if they just lie straight. Doesn't this need an inductive coil to produce a current?


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 Post subject:
PostPosted: Fri Jan 29, 2010 4:59 am 
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Cistron wrote:
I don't think the interference happens in the cables if they just lie straight. Doesn't this need an inductive coil to produce a current?

Nope. The problem is (likely) that a small signal is being induced on the lines and being amplified.

I have personally always found my "cell phone noise" comes from the wire between the sub and the computer. The sub's coil is almost always shielded (hold it up to a CRT to test?), though the PCB for the amplification probably is not.

Edit: PS if you are thinking about the fields, consider that the wire is not perfectly straight and will have some "area" for flux. Also the field change is non-uniform so even symmetric wire curves will generate different EMFs.


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 Post subject:
PostPosted: Fri Jan 29, 2010 3:06 pm 
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For interference from cell phones, just get a small anti-static bag and put the phone on top. It's usually enough to stop most speakers from picking up the buzzing noise.

It may reduce your reception slightly, but shouldn't keep you from getting a signal altogether.

If it's still bad, you could try putting the phone inside the bag.


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 Post subject:
PostPosted: Fri Jan 29, 2010 7:20 pm 
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Awesome, thanks for your suggestions you guys.

The case is an Antec P182 that's heavily lined with AcoustiPack sound-absorbing foam. I'm not sure much EMF is getting in there.

Based on all your input I'm pretty sure the subwoofer itself is the problem, and is amplifying the interference to the speakers. I can place my phone near the speakers or the wires and get little to no interference, but if I place my phone near the subwoofer it is significantly worse.

Because of the setup of my furniture I am very limited when it comes to placement options for the subwoofer; it's pretty much stuck where it's at.

Technically I could move the modem and router another ~5 feet away, but that seems like a temporary workaround rather than a solution. If I am able to open up the subwoofer, what could I line the inside with to shield it? The anti-static bags are definitely a possibility, although I was thinking more along the lines of lining the inside with chicken wire to create a sort of Faraday Cage.


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 Post subject:
PostPosted: Fri Jan 29, 2010 9:34 pm 
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Fëanor:

Check the power feed from the powerpack for the Subwoofer vs the audio signal feed from the PC.

...and please do get back to us with your troubleshooting results...

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Last edited by Wayne Redpath on Sat Jan 30, 2010 4:59 pm, edited 1 time in total.

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 Post subject:
PostPosted: Sat Jan 30, 2010 12:29 pm 
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Fëanor wrote:
Because of the setup of my furniture I am very limited when it comes to placement options for the subwoofer; it's pretty much stuck where it's at.

Could you open it up and line the box with tin foil? :D

Edit: just make sure you are not shorting something!


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 Post subject:
PostPosted: Thu Mar 18, 2010 7:01 am 
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swivelguy2 wrote:
It's probably actually the insides of the speakers that are lacking shielding, rather than the wires.


yeah i think your right...


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 Post subject:
PostPosted: Thu Mar 18, 2010 9:19 am 
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andymcca wrote:
Could you open it up and line the box with tin foil? :D

Edit: just make sure you are not shorting something!


And really make sure the foil does not rattle when the speaker is operating! That probably means it needs to be fully glued to every surface.

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 Post subject:
PostPosted: Tue Apr 06, 2010 3:05 pm 
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mb try no noise program


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