WTF is wrong with my speakers??

[amnesiac]

I currently have a set of Altec Lansing ACS340 speakers (w/ subwoofer) that I got from ComputerGeeks a couple weeks ago.. They've been working great until last night when I noticed a slight thumping which was coming from the sub. I thought maybe it was noise from the sound card, but it continued to pop and thump erratically even after I disconnected the input. It sounds like line noise but my satellites don't make a peep unless I tell them to. Anyone have any ideas? Dismantling the sub and/or throwing it away isn't completely out of the question. They were only $4.

 

[Mountain]

the speaker"sub" works but also makes bad noises? no problem with satellites or sub in playing what ever is coming thru the "line" out? "sub" requires own little amp with crossover, Is it possible there is a bad component in little amp or the coil"crossover". or is the sub getting the full range and the bottom is cut off by capacitors and sent to the subs? gotta know how the signal is being shaped. good luck. gc is "roasting me alive". see OFF TOPIC.

 

[amnesiac]

yeah the sub works fine but there's a constant "tremble" in the sub regardless of input and volume (I can turn the volume all the way down and disconnect it from the computer but a varying signal is still being sent to the sub). I was guessing it might be a problem with the signal being sent to the sub because there is no such "noise" signal being sent to the satellites at all.

From what I see it looks more like a capacitor cutoff system than a crossover (from what I know crossovers to look like). There's a ton of small ones and a big 10Kuf capacitor. Don't know why a faulty capacitor would cause this kind of anomaly though! The signal sounds like either bad/touching wiring or interference of some sort..

 

[AfterBurn]

Sounds (no pun intended ) like a ground loop. Is the speaker amplifier on the same power outlet as your computer? Do you have external sound sources hooked up to your computer through the line in of your soundcard? If so, unplug those and see if it stops.
If it is a ground loop, it can be a bitch to find the cause. :/