"Noisy" Speaker power

[kahlid74]

I have a pair of speakers that I have hooked up to the 12 volt connection from my Power supply.  The power supply is a decent one so I am suprised by the large amount of noice I can hear on the speakers when ever the hard drive does anything or when fans are plugged in.  What can I do to clean the power going to the speakers to prevent the other devices in the system from affecting the speaker quality?

[Doughbroz]

If you have speakers wired to 12 volt DC, you aren't going to have them for very long. 

[kahlid74]

Seriously?  What's the problem?  Do they need AC power or do they need a resistor on?

[Doughbroz]

Assuming these speakers are in a video game, they should be connected to the SPKR+ and SPKR- wires on the board harness.  The + terminal on the speaker sometimes has a red dot on it instead of a +.  If they are not marked, it won't hurt anything to have them reversed.  Just try them both ways and pick the better sounding hookup if you can tell a difference.  You can also test for polarity with a D cell battery.  Attach a wire to each end of the battery with tape or have someone hold them in place.  Disconnect the speakers from the game wiring and  momentarily touch the battery wires to the speaker terminals.  If you have the + end of the battery on the + speaker terminal, the paper cone will move outward (away from the magnet).  On a small speaker, this may not be visible, but you may be able to feel a difference by lightly holding a finger on the paper cone.  Some games have stereo sound and some do not.  If you don't know which you have, post the name of the game and someone here should know.   

[kahlid74]

It's actually a built from scratch bartop arcade machine.  It runs a menu system for different emulators.  The speakers are regular computer speakers made by creative.  They are hooked up onto a 12volt power connection from a computer Power supply inside the Arcade machine.

Anyone have any ideas on how I can clean the power or what I am doing wrong as to why the speakers have noise?

[commandcom]

I had a similar problem with my set up (car speakers though, not PC speakers).  I discovered there are potentially a number of causes for the issue:

• You may have a cheap power supply.  Some can leak noise (RMI/EMF) through the speakers and/or amplifier.  The only solution here is to get another power supply.
• Make sure your power supply is properly grounded.  Do not use one of those adapters that allow you to plug a three prong outlet into a two prong receptacle (provided you're in the US, of course)
• You may have a ground loop problem (http://www.epanorama.net/documents/groundloop). There are devices that will cancel out ground loops (try Radio Shack)

I'm sure any EEs in the forum could specify a number other causes for speaker hum.  My solution was to get a dedicated 12VDC power supply and use that to drive a car amplifier.

[whammoed]

This can be a problem in car systems too, you could try something like:
http://www.crutchfield.com/S-5ziMysBzY3N/cgi-bin/ProdView.asp?g=181150&I=003S15A