Barking Subwoofer Blues

November 1, 2006 1:51 PM

My mother-in-law plugged in her laptop via a docking station, hit the on switch on the powerstrip, and two disturbing things happened...

1) the external monitor's switch had been left in the "on" position, so there was a "bwong" noise from the monitor (sounded like a nasty de-gaussing, really)

2) the 2.1 speaker system started emitting this sound like "BWOooooom" every five seconds or so. It sounds kind of like bass feedback that builds relatively quickly in volume (not percussively, but a quick swell), then trails away (as if an electrical charge had been, well, discharged), and then it cycles up again.

By variously plugging and unplugging things, I narrowed it down to the subwoofer box itself. even with no input from the computer and the satellite speakers removed, powering up causes the feedback-y sound to start. It seems willing to continue forever, too.

My first thoughts were that perhaps some circuit or circuit protection in the subwoofer box had gone "poof" and the subwoofer was shot.

Any thoughts?

(BTW, if the subwoofer's toast, I'm definitely bringing it home to sample this sound -- it's killer!)

posted by I, Credulous to computers & internet (6 comments total)

The monitor sound you describe is not at all uncommon for CRTs when left "on" but without a signal. I wouldn't worry about it.

The speaker thing is a little strange. Try plugging the speakers into a different outlet and see if it stops. If it does, look for a fuse on whatever it was plugged into previously. See if you can reset it.
posted by odinsdream at 2:02 PM on November 1, 2006

The subwoofer is dead. For it to be making a noise like that with no input means something is wrong with the circuit inside. It's probably fixable if you have the inclination but wouldn't be worth paying someone unless it's better than the standard consumer-grade.
posted by 6550 at 4:14 PM on November 1, 2006

The other possibility is the power supply. Is it a separate device? If so you might have one of similar voltage and current rating that you could substitute, at least for testing.
posted by 6550 at 4:15 PM on November 1, 2006

The monitor sound is a common one—my old CRT Apple Cinema Display makes that exact "bwong!" sound you describe when it starts up again after being put to sleep.
posted by limeonaire at 4:48 PM on November 1, 2006

Try the subwoofer with some other audio source. If you have nothing convenient, or you are worried about damaging whatever it is that is convenient, try grounding the input to see if you can make it go silent.

If you are driving the subwoofer with a signal, do you hear it at all, or is it just the noise you describe?

Did you hear the degaussing noise yourself? It doesn't seem like a big deal, but if it was not the normal behavior it at least worth thinking about.

It is possible that it is all just coincidence, and the subwoofer has just chosen this time to give up the ghost.
posted by Chuckles at 7:16 PM on November 1, 2006

thanks for all of the replies.
i should have made more clear the fact that I'm not too concerned about the monitor -- I've caused my own monitors similar grief and never suffered for it. I only mentioned it because I thought there might be some issue with magnetic leakage or something equally magical...

the subwoofer makes the noise with no inputs plugged into it, and with or without the satellite speakers plugged in.

The subwoofer is made by A Open and actually has it's own internal power supply (a sign of some quality, I think). It connects to the power strip via a polarized two-prong plug.

I'm inclined to agree that it's toast, that it's just a coincidence that it up and died at this point in time (it is at least five years old, actually, it came with her previous PC)...I just need to do "due diligence" for her and ask around before she'd accept the pronouncement.

thanks for your help and suggestions.

peace,
posted by I, Credulous at 5:05 PM on November 2, 2006