Axiom Home Page Forums General Discussion Home Theater Sub woofer hum

I had a concern a while back about sub woofer hum. I just thought I would let everyone know what the fix was.

It was a ground loop which was only audible when the rogers cable was hooked up. I ran a wire from the chassis of the amp and touched one of the screws on the back of the sub and the noise went away. So I ran the wire from the amp the the electrical outlet ground. Problem fixed.

glad to hear that

did you notice it was especially bad when listening to the radio? i had the same problem (which i fixed soon because i had a feeling it was a grounding issue), but when listening to the radio the sub hummed even more then normal.

could someone explain the physics behind grounding a speaker? i always wonered why you would need to ground a speaker. it seems to me like the audio signal would be separate from any interference.

He's not grounding the speaker; he's grounding the subwoofer amp. I think (going out on a limb here) that since speakers are DC, they are already "grounded" as a part of the circuit.

I didnt notice any difference when the radio was on. The sub would not go into stand by while I had this problem. As for the ground issue with speakers dont forget the sub has its own amp.

Thats correct about grounding the amp.

Hi kcarlile,

A slight correction: the audio signal from your amplifier or receiver's output that drives your loudspeakers is an AC signal, not DC. The push-pull action of a speaker driver--a cycle of compression where the cone pushes outward and compresses the air molecules, then reverses itself, moving in the opposite direction, creating a rarefaction (an expansion) only works with an alternating signal. It is the alternating signal through the voice coil within the fixed magnetic poles of the speaker magnet that make the speaker driver what it is--a reciprocating electro-magnetic motor.

DC is the last thing you want to enter a loudspeaker. That's exactly what happens when an amplifier goes into overload and "clips" off the tops and bottoms of the AC audio signal, sending a DC signal into the driver voice coils, causing them to melt, fuse and burn out.

Regards,

My bad. Should have remembered that. Dur.