[Elecraft] K3 - speaker buzz

[Paul at N4LCD.com]

>A month or so ago there was a flurry of posts about buzz in the 
>speaker.  On poster replaced fiber washers used to mount the 
>speakers with neoprene and reported good results.
>
>With my sidetone level set at about 45, I heard pronounced buzzing 
>at 350 and 400 Hz sidetones.  (Adjust your sidetone level with MON, 
>then go to PITCH and adjust the sidetone pitch throughout its range.)
>
>Since I had to pop the top to install my back ordered 6kHz filter, I 
>took the opportunity to replace the fiber washers with improvised 
>ones made from small grommets sliced in half.  I did get some improvement.
>Now the major buzz is limited to 350 Hz.  In putting some slight 
>finger pressure at various places on the top cover, I see that the 
>speaker isn't at fault but that the top plate has some 
>resonances.  I'm thinking of putting some kind of resonance killers 
>on the underside, maybe some globs or beads of RTV or similar, so as 
>to avoid any kind of permanent change to the rig.

Car stereo installers use a thin but heavy black mat with adhesive on 
one side to dampen resonances in door panels.
It's also used on the inside walls of computer cases to dampen fan noise.
A few of their throw-away scraps stuck on the inside of the cover 
would probably fix you right up.