Re: Mic question.

[Mike Curtis <wd6ehr@xxxxxxxxxx>]

> 
> On Mon, 27 Mar 1995 elliott@xxxxxxxxxxxxxxxxxxxxxxxx wrote:
> 
> >  The crystal mic elements are fragile.  Like several other people have
> > said, my JT-30 has taken a few minor drops w/o any problems.
> >  However, extreme heat will kill a crystal.  I learned the hard way
> > after leaving a mic in a car on a hot summer day in South Carolina.
> >  I try to give my JT-30 as much TLC as possible.
> 
>  I've rigged up a case for my mics. I took a zip-up cloth portable 
> cassette case (available in most record stores for less than $10) and 
> lined it with foam rubber packaging material on both sides. The result - 
> a case that holds two bullets and a vocal mic firmly. It is waterproof, 
> shock resistant and provides insulation from heat and cold.

The Green Bullet uses a controlled magnetic cartridge, which is a lot more
rugged than a crystal.  The Controlled Magnetic has a magnet and coil with
a movable center.  This may or may not be magnetized, depending on the
specific design - a separate magnet would permit higher flux density and
therefore higher output.  This movable center ("armature") is connected to
a piece of fairly thick wire (maybe 19 AWG???), which is connected to the
microphone diaphragm.  Because of the mass of the moving parts, treble is
all but totally eliminated.  Also, because of the stiffness of the
diaphragm, the element has little bass response.  It's inherently a very
midrangey design, which sounds good for amplified harmonica. 

Controlled magnetics used to be very popular in voice communications 
applications.  They have been all but completely replaced with dynamic 
and electret based microphones, although certain crystal and ceramic 
microphones still enjoy great popularity.  A prime example is the Astatic 
D-104, nicknamed "the Lollipop" because of its resemblance to a large 
chrome lollipop.


 -- mike