[Asterisk-Users] Should echo cancellation be a "science" or an "art"?

[Ken D'Ambrosio]

Perhaps 90% of my calls -- over a Uniden and a Grandstream -- are fine.
The other 10% get some nasty echoes.  Is there some magic something I
should be tweaking?  I kind of thought that echo cancellation was
static, rather than dynamic, and that it's difficult to be able to cope
with something like this.  Am I (hopefully) mistaken?  Any pointers on
what to do about echo cancellation would be much appreciated...

Thanks,

-Ken