One set of gains that works is
0.2357 0.2357 0.2357 0.2357 0.2357 0.2357
1.0000 -1.0000 0.0000 0.0000 0.0000 0.0000
0.0000 0.0000 1.0000 -1.0000 0.0000 0.0000
0 0 0 0 1.0000 -1.0000
I put a write up on how to derive those at:
http://www.ai.sri.com/ajh/ambisonics/umashankar_velan.html
--
Aaron (hel...@ai.sri.com)
Menlo Park, CA US
On Sat, May 26, 2012 at 12:41 PM, umashankar mantravadi
<umasha...@hotmail.com> wrote:
>
> assuming all six capsules have same gain, and all are contributing to W, how
> much should be the attenuation? umashankar
>
> i have published my poems. read (or buy) at http://stores.lulu.com/umashankar
> > Date: Sat, 26 May 2012 18:25:04 +0200
>> From: netti...@stackingdwarves.net
>> To: sursound@music.vt.edu
>> Subject: Re: [Sursound] microphone epiphany ?
>>
>> On 05/26/2012 04:51 PM, Augustine Leudar wrote:
>> >> Hi Michael,
>> >> thanks for the reply - there is no doubt Ive missed something !
>> >> I am aware of the need for W coordinate and have included it in my encoder
>> >> as instructed although I have to admit I am still not clear on its
>> >> function - but my question specifically relates to the information gained
>> >> from the 3 fig of eight patterns gained form a mic design such as this
>> >> one :
>> >>
>> >> http://www.shapeways.com/model/143678/velan-140-internals.html
>> >>
>> >> Am I right in thinking the W component gives you enhanced distance
>> >> information for a given sound source ?
>>
>> we cannot hear absolute phase, so if you are listening to a figure of
>> eight microphone, there is no way to tell whether the sound you're
>> hearing was coming into the (positive) frontal lobe or the (inverted)
>> rear lobe. hence, the only information we can get from a lonely fig8 is
>> "it's obviously not coming from the side".
>>
>> now if you add an omni to the equation, all of a sudden you have the
>> possibilty to discern between the two lobes of the fig8: one is in-phase
>> with the omni, the other isn't.
>>
>> thus, the 0th order component helps you resolve the ambiguities of all
>> the 1st order signals.
>>
>> btw, if you move to second order, the situation is the same: with a
>> cloverleaf directivity, you only know "it's either coming from
>> front-or-back, or from left-or-right". only with the first-order
>> information, the ambiguity can be resolved.
>>
>> W also has a subtle role in distance coding, but its main job is really
>> to help us make sense of the fig8s.
>>
>>
>> to wrap up, three real fig8s won't ever give you ambisonics. but if you
>> obtain the fig8s by subtracting two back-to-back cardioids, you can also
>> add them, which then gives you a nice omnidirectional component. note
>> that you will have to attenuate the resulting omni signal according to
>> the number of capsules you used.
>>
>>
>> best,
>>
>>
>> jörn
>>
>>
>>
>> --
>> Jörn Nettingsmeier
>> Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
>>
>> Meister für Veranstaltungstechnik (Bühne/Studio)
>> Tonmeister VDT
>>
>> http://stackingdwarves.net
>>
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