If I remember correctly there was a fortran program written by Angelo Farina 
that could recover a ambisonic signal in 2 dimensions from a 5 microphone  X 
setup.
I mic in center and 4 mics in a square around that.

I guess we could use just omni 4 mic's in a cross to get the needed information 
for creating horizontal XY signals. 

The closer the mics are to each other the higher the frequency resololution, 
and the longer they are from each other the better for recovering low frequency 
direectivity info - this is my theory.

There have been figure of 8 mics created by using 2 capsules besides each other 
to extract the differential preassure gradient.

BR Bo-Erik

-----Original Message-----
From: Sursound [mailto:sursound-boun...@music.vt.edu] On Behalf Of Curtis Alcock
Sent: den 13 maj 2015 07:24
To: Surround Sound discussion group
Subject: Re: [Sursound] Sursound Digest, Vol 82, Issue 2


>> It's still a dreadful mike, after using plenty of ressources to 
>> "design" a non-optimized WXY mike.
> 
> Yes, the positions of the mics are really suboptimal to put it mildly. 
> Many of them will just produce redundant information.
> 
>> Maybe it is only me, but what was/is the < motivation > to do things 
>> in that way?


I suspect the motivation WAS to (deliberately) provide redundant information. 
The author writes that "distance between microphones being 5 cm and the largest 
being 21.8 cm." 

So perhaps the goal is NOT to use all the information at any one time, but to 
provide enough versatility within the (library of) material for (random 
unknown) developers of noise reduction algorithms to test various scenarios 
specific to their needs. The algorithm developer could test differing 
beam-forming options that best met their own application by choosing which 
subset of the 16 microphones channels to use, depending on how great a distance 
they wanted between the (presumedly omnidirectional) mic ports, for example. 
And for developers to explore which combination of two (or more) mic ports 
provides optimal signal enhancement.

But I'm just reading between the lines as unfortunately the website does not 
appear to explain any further.

Which means that it's probably not necessary for me to use all 16 channels to 
convert to a B format file? 

Perhaps I only need to take a subset of the channels and use a matrix 
convolution software (I'm on Mac)?
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