[Harp-L] Low and High Pass Filter to fight feeback?

[Mike Fugazzi <mikefugazzi@xxxxxxxxx>]

Anyone ever use these?  If so, at what frequencies?  I am assuming a
decent amount of bass and high end feedback rings at frequencies that
actually don't matter to the sound of the harmonica.  In otherwords,
when played, the harmonica doesn't even reach that low or high of a
sound.

Thanks!