[Elecraft] K3 Speaker buzz - But which external speaker ?

[g4sgx at justfans.co.uk]

Hello,
Well after 18 months the buzzing of the K3 internal speaker has  
reached annoying proportions.
For a while it faded after switching on for 10 mins but now its a  
constant resonance at 580 Hz. Great for CW! (not)
Because of the above I am sure its because the coil has shifted in the  
speaker slightly rather than any sympathetic resonances from the case.

I'm not complaining, I understand if I contacted Elecraft I am likely  
to get a replacement speaker sent out, (Its a well documented 'extra  
feature') but really haven't got round to it, nor am i likely too,  
well down the list of priorities!
Will probably order it along with a set of CW filters when I need them.

I'm REALLY after recommendations for an external shack speaker, or is  
any good HiFi speaker good enough? I would assume some RF shielding  
and good high end sensitivity was more of an issue.

Yours.
Iain G4SGX.
Happy K3 Owner :)