[Boatanchors] [AMRadio] Dreaded D-104

[David C. Hallam]

I have never had anyone comment one way or the other about the "quality" 
of my signal.  I operate only boat anchor SSB and have several 
microphones of  two different types.  One type one is the Turner 22X 
crystal microphone, and the other is the Turner 95D high impedance 
dynamic microphone.  The 95D is the microphone Collins called the SM-1.

David
KW4DH

On 10/6/2011 11:43 AM, Richard Knoppow wrote:

  The "tinnyness" is typical of crystal and ceramic microphones. They 
look like capacitors; the impedance seen by microphone acts like an RC 
high pass filter so the input must be very high if the low end is not to 
be attenuated. OTOH, research by Bell Labs into speech characteristics 
some eighty years ago, and confirmed many times since, shows that most 
of the power in male speech lies below 500hz but contributes only about 
2% to articulation. where bandwidth or power is limited the low end 
should be rolled off. The most important frequency range for 
intelligibility is between about 1khz and about 3khz. Microphones 
designed for high intelligibility speech generally boost this range and 
roll off the low end. Naturalness requires more of the low end which is 
why Bell System transmitted down to about 250hz for telephone service. I 
am puzzled as to why an EV 664 would sound muffled, it actually has a 
slight rise in the intelligibility range. The 77D and DX have a 
frequency response which varies with the directional setting; for 
bi-directional it drifts down toward the high end, for non-directional 
it has a definite peak around 4500hz and in unidirectional the two 
combine to a curve with a slight rise at 4500. If you use the mic in 
non-dirctional and set the roll off switch on the bottom for 2 you will 
get a pretty good communicaions type response. I was trained on RCA mics 
by the head of microphone production at Camden and know the 77 series 
pretty well. They should not sound muffled and should not need 
equalization. If your mic doesn't sound smooth and fairly wide range the 
ribbon may have been damaged (easy to do) or not installed correctly. 
The 77D/DX was never my favorite for music recording but is a good voice 
mic. -- Richard Knoppow Los Angeles WB6KBL dickburk at ix.netcom.com 
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"There are two means of refuge from the miseries of life.  Music and cats." ~ Albert Schweitzer ~