mic body and grille effect on sound

seavote

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i've seen a few comments on this subject in the mic meta,but not
much. can anyone relate some basic rules of thumb? theoretical ideal
body and grille?best materials to use? i just obtained about 15 feet
of 2" copper pipe and would like to design and build some different
bodies with various grill designs and materials. thx
 

adamasd

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The grill acts as a filter, the opening in it alter the sound. The mic element itself is in the shadow of the the body, the sound waves can not approach the mic from those directions. Sound waves can also reflect off of any hard surfaces in the mic creating ringing and artificats. There is an article in the mic meta, I think it is the BBC ribbon mic document, it covers alot of the grill and body stuff. There are also a few articles on building condensers, they cover some of this as well. Just download and read all of the old articles on mic building in the meta, there are quite a few, they should answer alot of your questions, if not they will at least allow you to ask a more direct question that is easier to answer.

adam
 

MATTI

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Here is U 47 grille
http://mixguides.com/microphones/vintage_products/audio_vintage_microphones_part/
 

Marik

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[quote author="seavote"]theoretical ideal
body and grille?best materials to use? i just obtained about 15 feet
of 2" copper pipe and would like to design and build some different
bodies with various grill designs and materials. thx[/quote]

Theoretically, the ideal body and grill is no body or grill. Practically, look at the Gefell bodies--it will give you a clue.
I highly doubt somebody would tell you a rule of thumb--every design is just a different set of compromises. It also very much depends on the sound you are looking for. Don't forget, very often for a good microphone designer the grill construction is a complimenting part of other mic components.

Search the forum for "mic grill", read Stephen Paul's article, and experiment a lot.

As an encouraging note, it took me half a year of experiments to build a grill I wanted... and still working...
 

Gus

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One thing to try.

Build two as close to identical circuits as you can. I built two fet ones with two fets picked from a bag of 1000 that are matched.

The Mxl 32mm capsules seem to be fairly close to each other.

I have the circuits mounted in two different body grills. They sound very different. I can even move the capsule and it follows the body. A few lab member heard them.

You just need to build/test a lot. Then measure things and take notes.

I don't think anyone that does all this work will post it on the web.

As Marik posted look close at the Gefells. Do you want that? maybe not.
 

seavote

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thanks. adamsd, i'll check out that meta. i'm not planning on building a ribbon so i didnt make it to those threads. U47 article looks good. as to the no grille or body theory, i was thinking the same thing myself. then again in the real world a grille that compliments the mic is ideal. but to just blindly try different designs, adjusting and improving could take years. (ok i know you would learn as you went so eventually your designs would not be blind) to build the least intrusive body and grill seems more practical as it could most likely be used with different circuits and capsules. i'll be recieving 2 g7 pcb sets and ive sized up some bodies according to the original article(2" copper pipe).in the photos it looks as if a 1/4" rib is left on the top of the mic and dividing the two openings to the capsule. i'm going to go with 1/8 or 7/64s if i can make it happen. grille wise tim campbells design seems like it would affect the sound less.i'll give that a go too.
wish me luck
 

seavote

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marik, thanks the gefell web site has a great deal of info on the subject as well as info on mic design in general. i'll definitly try a "geffell like" design.
 

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