Help with weird buzz

[davman]

I note that in #1 you say this problem occurs with speaker unpowered & bass coming from another source.
I noted a similar hi-pitched buzz today, coming from a VOX pathfinder combo when playing a test tone (100Hz) at fairly high level, thru its speaker.

The fault was traced to the plasticsed fabric on the front of the speaker (which was vibrating quite strongly). The buzz disappeared when I put my finger gently on the centre of the fabric .
The fabric was in perfect condition & fairly new, but I suspect the plastic weave threads were resonating & hitting each other - giving the nasty buzz.
This effect disappeared when the level was reduced.


Possibly your problem too?

[Richard]

How are you going to fix this? Are you talking about the surround?

[Cretins]

Hi davman, thanks, I noticed the other day that my buzz was returning after being eliminated by removing the old gasket. The buzz was gone for two days and then it returned albeit not as bad as before but it sure as hell is there. Mine's not really a high pitched buzz as it's only noticeable when playing D and lower notes. And my speaker cone actually vibrates, with no power to the speaker, playing another amp in the room, I can see it vibrating, I can touch the cone lightly with my finger tip (while a bass note is played on another amp) and it will stop with pressure from my finger but when I release my finger the buzz returns again, and again , and again for as long as the note sustains. So it's back to the drawing board for me, unfortunately I'm too busy with other projects at the moment and so I just retired this Blue to the back room til I can find some time to delve a little deeper into this mystery.

[davman]

How are you going to fix this? Are you talking about the surround?

No, not the surround.
In my case, the buzz was coming from the speaker grille fabric (buzz stopped when I touched the centre of fabric) - and you could see the grille cloth resonating!
If it was soft cloth, maybe it wouldn't buzz, but I suspect the woven threads were of a harder material, hence the problem.

Admittedly, this was a cheap practice amp which had a new speaker fitted. The buzz from the grille only happened at very high volume levels, so would not normally be a problem.

I suppose it could be fixed by gluing a small weight (coin?) to the inside-centre of the grille cloth -to restrict movement.

[davman]

Hi Cretins! Mine produces its hi-pitched buzz when I put a 100Hz tone into the speaker.
If you are actually putting your finger on the cone rather than the grille cloth, then it sounds like there may be a split in the cone - maybe where it attaches to the voice-coil.
Good luck.

[rjb]

Something akin to the 'laying on of hands' mentioned by RJB in this thread.
http://music-electronics-forum.com/t29623/

I thought I felt my ears burning.
To save readers from sifting through the entire thread (entertaining as it may be), here is a direct link to the mentioned post.
http://music-electronics-forum.com/t29623-5/#post261921

-rb

[rjb]

It's called "troubleshooting". Ya did all right

How come when I do it, it's called "dumb luck"?