[Elecraft] My KX3 desk microphone project

[Harry Yingst via Elecraft]

Anything Specific to just the actual elements being in parallel?
I do now there is one commercial mic doing this and is supposed to have good reviews.



      From: Walter Underwood <wunder at wunderwood.org>
 To: Harry Yingst <hlyingst at yahoo.com>; "elecraft at mailman.qth.net" <elecraft at mailman.qth.net> 
 Sent: Sunday, January 25, 2015 3:57 PM
 Subject: Re: [Elecraft] My KX3 desk microphone project
   
You could start with these two, read “close miking” in the Wikipedia article. The second article is about speech recording for oral historians, so that is fairly applicable to voice communications. Neither article even mentions using multiple microphones for one person. The Wikipedia article section on stereo recording gives a hint of some of the strange things that can happen with multiple mics.

http://en.wikipedia.org/wiki/Microphone_practice
http://ohda.matrix.msu.edu/2012/06/understanding-microphones/

Multiple microphones act very similar to phased arrays of antennas. They have directionality and nulls that change with frequency. With a source in one position, they can have a frequency response with a number of peaks and nulls. This is called “comb filtering”.

This article goes over that, including the 3-to-1 rule: "There is a popular microphone placement adage that is known as the 3 to 1 Rule. The 3 to 1 Rule says that if multiple microphones can hear the same source, then no other microphone should be less than 3 times the distance to the source for the microphone nearest the source. In other words, if a person is talking into a microphone that is one foot away from them, then no other microphone in the room should be closer than 3 feet away from that person in order to minimize comb filtering."

http://support.biamp.com/Tesira/Miscellaneous/Comb_filters

wunder
K6WRU
CM87wj
http://observer.wunderwood.org/



On Jan 25, 2015, at 12:31 PM, Harry Yingst via Elecraft <elecraft at mailman.qth.net> wrote:

> Can you please provide a reference for this?
> 
> 
>      From: Jim Brown <jim at audiosystemsgroup.com>
> To: elecraft at mailman.qth.net 
> Sent: Sunday, January 25, 2015 12:48 PM
> Subject: Re: [Elecraft] My KX3 desk microphone project
> 
> On Sun,1/25/2015 5:20 AM, Gary - NC3Z wrote:
>> In my opinion much, much better words should of been choose than 
>> "seriously misguided", they have connotations that one is an idiot. 
>> Seriously misguided would be trying to run a 12V device off 120V. 
> 
> Why? If an idea is seriously misguided, saying so is entirely 
> appropriate. I did not expand on the advice because this is an email 
> reflector dedicated to Elecraft radios, not microphones.
> 
> There are (at least) three reasons why an array of microphones is a 
> really bad idea. First, really good sounding mics to work with our 
> radios are widely available cheap. Second, a microphone is an 
> electroacoustic device -- it collects sound at a point in space and 
> converts it to voltage. A microphone at a different point in space 
> collects different sound -- there is a difference in time between those 
> sounds, which results in a difference in phase. The difference in phase 
> results in peaks and dips in the frequency response, which in the audio 
> world is called comb filtering. Third, one mic loads another 
> electrically, degrading the performance of each.
> 
> Third, those of us working in pro audio learned a long time ago that one 
> mic feeding a single channel is always better than one for picking up a 
> single sound source like the human voice. Putting more of them in 
> parallel does not make them work better.
> 
> When you see two mics on either side of a podium, it's an indication 
> that whoever put them there didn't understand that. As the talker moves 
> side to side, the sound of his/her voice changes due to the 
> cancellation. Almost 40 years ago, I did a couple of big outdoor sound 
> reinforcement gigs for the President, and the White House sound 
> engineers DID understand that -- they studied at the same workshops that 
> I did. They had Shure build a special mic for them with three capsules 
> in it, each coming out on their own shielded twisted pair. Two went to 
> me, the second was for redundancy -- in case wiring for the first one 
> failed. Each went to a different input of my mix console. The third went 
> to them for their recording.
> 
> 73, Jim K9YC
> 
> 
> 
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