My client says when she turns on the ceiling fan for the patio, the subwoofer thumps. This switch is about 30-40ft away. The breaker box is about 15 ft (as the crow flys)from where the sub is. My client tried other outlets throughout the house and it continued to happen. Then he left the sub woofer unplugged and it still happens(should of tried that first).
The pre-wire was done by the infamous alarm company. Oh, the sub is connected via 4 conductor speaker wire. My guess is the romex going to that switch is running next to the speaker wire for the sub. I know the best thing to do is to bypass the prewire cables and run new ones and that will diagnos it. I'd just like to hear some other ideas before I go out there.
Thanks,
CMack

First thing I would do is instal a new Fan switch. Certainly seems to me that that should NOT happen... I'm sure Larry may have another idea....

Moi? Oh, okay.

When you say, "he left the sub woofer unplugged", I hope you mean the speaker wires. (I can't imagine a sub thumping without power!) Meanwhile, try a substitute wire, even if just laid on the floor. Use a process of elimination, and make only one change at a time.

Motors are inductive loads, and thus are known to cause contact arcing. Is the thump dependent on fan speed setting (capacitors) and/or is there a wall switch/speed control, or just operated with pull-chains?

Larry
www.fineelectricco.com (temporarily down)

Larry,
The sub was unplugged from the power oulet and the speaker wires were still plugged in and the thump still happened.
The client is no big hurry to get this resolved so I'll wait for more info before I get back there.
The client stated it happened regardless of fan speed.
There is a regular light switch that passes power to the fan and the speed is regulated at the fan via a pull string.
CMack

Is the preamp that the sub is attached to being powered on via a switched outlet?

Matt,
No.

CMack

Any other thoughts?
CMack

So I'm assuming that the fan and the Preamp/Receiver are on the same circuit/phase. Try running an extension cord to an outlet not on the same circuit, or phase, that the fan is connected to. See what happens....

There is another tack to try on this one: see if the subwoofer thumps when it has been taken to another room. Or even county. I mean, disconnect the subwoofer and move it completely away, then stand where the subwoofer was and see if there is a thump under the same circumstances.

I had a customer complain about hum from his sub, hum that was not always there. He had tried everything he could think of, and it hummed even when unplugged the sub. Same scenario.

I went out there and verified it. So I disconnected the speaker wire. It still hummed. I walked around a bit and discovered the subwoofer was on the other side of a wall from his refrigerator. The refrigerator was humming. It had always hummed, but here is the key: once there was a subwoofer, HIS ATTENTION WAS ON LOW FREQUENCY SOUND FOR THE FIRST TIME IN HIS LIFE and he heard the refrigerator. Since the subwoofer was a new element in the room, he assumed the sub was the source. It made no sense that the sub hummed when unplugged, so he called me.

Which brings me to a little rule I have for such things: Don't be too quick to believe that your customer has accurately described the problem. My customer said that his subwoofer was humming and he did not like it. His problem was that he could hear hum and he did not like it. He assumed the sub caused the hum, and therein was the confusion for me as well as for him.

I learned this lesson most thoroughly when a customer told me that some channels did not work on one DSS reciver, and some other channels did not work on a different receiver. Talk about confusing! I verified it, but then found that one polarity of signal was absent. HE DID NOT USE THE TWO RECEIVERS FOR THE SAME SETS OF CHANNELS, so he did not realize that they both could not get the same channels. Again, confusion.

confusion is right, You (Ernie) have me confused to all ends on that last paragraph about the channels... please explain cuz this is going to drive me nuts.

He said that one polarity of the satellite signal was out. Either left-hand or right-hand polarity. Meaning certain channels were not available because of it.