Re: [Harp-L] what makes a mic prone to feedback?

[Grbullets2@xxxxxxx]

In a message dated 1/6/2006 8:49:19 PM Eastern Standard Time, 
garry@xxxxxxxxxxxx writes:
in the recent discussions of mics, several people commented
on this mic or that being resistant to feedback.  that got me 
curious as to what aspects of a mic's design contribute to this.
impedance?  shape?  pickup pattern (omni vs. cardioid)?  
element type?  is it all black magic, or is this well understood?
if the latter, what are the tradeoffs a designer makes?   i.e. what
does he give up for feedback resistance, or what does he get
that would be worth a feedback prone mic?

         All of these things actually are involved,but for the most part,it's 
the very strong signals that the mics have.The high gain mics that most of us 
use have an input signal thats much stronger than a guitar signal.That,along 
with the high gain of the preamp of most GUITAR amps causes the amp to squeel 
like a pig.Some mics are much stronger than others and will feed back more 
than the lower gain mics.Shielding the mic element helps if you have a wood or 
plastic mic.The mics pickup pattern also affects feedback.Most mics that are 
less prone to feedback are the ones with weaker input signals.I'm sure you'll be 
hearing alot on this subject.It's just something that harp players have to 
work around finding the right mic and preamp tube combo.There are also amp mods 
that can be done which usually will affect the amps tone in one way or another.