Subwoofer humming

[Sir BoD]

Not that kind of hum.

It's been happening for some years now and I suppose I ought to get new speakers. The strange thing is, if I tap the woofer, the hum goes away temporarily. Then, v-e-r-y slowly, it starts to come back, sometimes taking 20 minutes to get up to full pelt.

I've done a bit of research (Googling) and I've read about ground loop hum, but wouldn't it just hum all the time regardless of whether I've given it a good hiding?

I've disconnected the other speakers, put the volume down and made sure the woofer is away from other cables and interference, but it still does the same thing.

Any ideas? Cheers.

 

[John Marwood]

Sony Walkman

You heard it here first

 

[Gramaisc]

Does it have an internal power supply?

Are you sure it is the speaker cone that is humming - or could it be a 'mechanical' hum from a transformer mounting issue?

 

[Sir BoD]

Does it have an internal power supply?

Are you sure it is the speaker cone that is humming - or could it be a 'mechanical' hum from a transformer mounting issue?

I really don't think it is a speaker hum. It sounds like it's coming at the top of the casing near the front where there controls are for the volume, mute and bass boost.

 

[Gramaisc]

Does it have a mains lead?

 

[Sir BoD]

Yes it does. Shall I cut it in half?

 

[Gramaisc]

I suspect that you may have a transformer hum - do you have access to the insides?

 

[Gramaisc]

I suspect that you may have a transformer hum - do you have access to the insides?

You may find something like this - the four screws in the corners serve to clamp the core laminations together - looseness can cause buzzing.

Also, the mounting screws/nuts need to be tight - and what they're mounted to needs to be solid, ad infinitum.

Low frequencies are good at loosening things.

Obviously, do this whilst it's unplugged, and give it half a minute for any capacitors to drop.

 

[Sir BoD]

You may find something like this - the four screws in the corners serve to clamp the core laminations together - looseness can cause buzzing.

Also, the mounting screws/nuts need to be tight - and what they're mounted to needs to be solid, ad infinitum.

Low frequencies are good at loosening things.

Obviously, do this whilst it's unplugged, and give it half a minute for any capacitors to drop.

Cheers Gram. If I'm not back in 1/2 hour you can have my Peters and Lee LPs.

 

[Sir BoD]

Right, early days yet, but there is only a slight low hum now, which I suspect is because they're old speakers old and is not the same hum as was before. I'll give it another 20 minutes before I'll be convinced that the other more pronounced hum isn't coming back.

I'll thank you anyway Gram, even if it doesn't end up working just for taking the time to reply.

 

[Gramaisc]

The actual speaker itself shouldn't ever hum, unless it is being told to, no matter how old it is. Sometimes, the suspension can degrade, allowing the coil to grate on the magnet, but that's not really going to give a sound that anyone would call a hum.

The hum will either be a spurious signal to the speaker or a power supply issue, almost certainly.

if the hum changes at all when the case is knocked, it more than likely a 'mechanical' issue.