Loose magnet on woofer?

[speaker dave]

It happens in the box, but not out of the box, so that excludes loose dustcaps and surrounds and pig tail leads.

Clearly the box is resonating when the buzz happens, as he can feel the vibration and it goes away with a light touch of the magnet.

 

[Brian Oshman]

Out of the box the basket is not rigidly mounted thus counterforce is reduced. Try running some epoxy around the magnet/basket joint then dum dum it up with the duct seal.

 

[Brian Oshman]

What is that first one?

It is like a clay substance used to seal electrical conduit so condensation doesn't form when passing through walls of different temperature extremes. It stays pliable and is dense and conforms to any shape. Very useful for damping vibrations in audio applications too on irregular shapes.

 

[davidgale]

"If I apply some pressure with my fingers to the back of the magnet of the woofer the buzz disappears (however it is strange that there is no buzz when I pull the woofer out of the enclosure " How is this accomplished when the speaker is still in the box ? Big port access?
It is most likely if the cone is polypropylene that you simply have a loose dust cap , run a thin blade at the dust cap and cone junction to see if it lifts. You havn't mentioned a brand name so if they are elcheapo's a good squirt of PVA wood glue to all internal box junctions wouldnt be wasted.

Yes, I reach the back of the woofer through a vent.
Wouldn't it be the case that if the problem were loose dustcap the ill effect of it would be more obvious, throughout the whole effective frequency range not only on some certain freqs? Visually I can't detect anything wrong with the dustcap, the joint is firm and tight.

 

[davidgale]

Today I've got some spare time and inspected the woofer more thoroughly. As you can see in the first picture, there is some serious gap between the basket and the magnet. I believe it should have been filled completely with glue (and actually there is some deeper in the gap; I also inspected the midrange driver, that gap indeed is sealed with glue). What I did was try to stick some rubber pieces in that gap. And guess what, the buzz significantly reduced. Is it safe to fill that gap completely with glue?
Also as you can see in the second picture, there are gaps between the spider and the cone. Should i fill them with glue?

 

[speaker dave]

The gap alone doesn't mean that there is movement or buzzing, but if some rubber in the gap (between magnet and frame) made a difference then go ahead and add a good bead of glue. I'd recommend a rubber or contact cement, or perhaps a wood glue that stays somewhat soft. Don't use something runny like super glue that might run in and get on the voice coil.

I would not add glue to the woofer cone.

David S.

 

[servasol]

1st answer

The fault may lie in the alignment of the coil to pole , a slight offset coupled with a small blister on the coil former will be enough to cause a poling effect. Check to see if there is a slight warping of the baffle or speaker basket , reinstall the driver with new foam sealant tape but dont over tighten the securing screws then slowly tighten the screws to see where the poling ocurrs when you apply a contant 120Hz. When you have the driver out being tested apply downward force on the out basket rim to see if you can replicate the poling , if there is a is poling lift the upper suspension of the basket and reset/realign for best clearance and reglue. An application of epoxy between the magnet and frame may help if the alignment is correct. However with a problem like this if it is an expensive speaker then fully recone or lesser product replace.

😀

My first answer was correct re application of expoxy between frame and magnet . It appears to be a plastic basket which are notorius in coming loose if the box has been dropped