What can make a speaker vibrate (buzz)?

[RMutt]

Thanks for taking the time to do that Geoff. if I can find some time I'll have a go this weekend.

[alphaGT]

I've worked on a few old speakers, and once I had a sudden vibration, loud flapping sound, and come to find out a shim of cardboard had fallen into the bottom of the cabinet. Just laying in the bottom. Where it came from I have no idea, probably glued in a corner or something? But just a loose piece of cardboard. And I've also had to deal with speaker wire touching something, I tacked it with glue every foot or so to the inside corner, but it was vibrating at a certain frequency, so I had to run a bead of caulk over the entire wire to quiet it down. And a loose screw, an over tightened screw that would not tighten up well, vibrated at a fairly high frequency. It could be a very low tech problem.


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[RMutt]

A couple of people have now mentioned other sources of vibration like loose braces, wires etc. Does the sound from these transfer to the driver? When I put my ear to the cone the sound definitely comes from there. Given the previous trouble I had and what Geoff, Dennis, Danilo, et al have suggested l have to think it is a cone/voice coil issue. Thanks everyone for their suggestions. AOS at its best.

[anthonyTD]

Sometimes the actual speechcoil wire can become loose on the former [Due to excesive heat, or just age] and it can cause the sound your refering to.
The glue, or resin holding the wire to the former can just deteriorate natuarly over time.
I have also had speakers where the speechcoil former has become partialy detached from the cone, again, where either the glue has broken down, cracked etc.
The glue holding the pig tails to the cone can also crack, and allow the pigtail wires to resonate at certain frequencies too.
These are all common faults I have seen over the years.
Of course, there may be nothing wrong with the speaker, and it could just be that the amplifier, and speaker combination are borderline stable, and at certain frequencies, they become unstable, causing a distortion.
Either way; Hope you get it sorted.
A...

[alphaGT]

A couple of people have now mentioned other sources of vibration like loose braces, wires etc. Does the sound from these transfer to the driver? When I put my ear to the cone the sound definitely comes from there. Given the previous trouble I had and what Geoff, Dennis, Danilo, et al have suggested l have to think it is a cone/voice coil issue. Thanks everyone for their suggestions. AOS at its best.

The short answer is yes. When that loose cardboard was in the cabinet, I could have sworn it was a bad driver. But removing the driver from the cabinet proved that it wasn't. The noise did not follow the driver, away from the cabinet. But it had me fooled until I did.


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