Hi, I know what I need to do - I just want to find out why Im doing it. The components were not expensive at all - the mic is already built and working fine. I am now just writing the encoding software in max . Phase inverting one channel is not rocket science neither is normalisation. Sphercal harmonics is way outside my field of expertise and I do not have the maths to be able to understand it yet (though I may learn) , however the PHD ambisonics students next door did give me an explanation to do with cosine being on the opposite side with the capsule facing away - he wasnt entirely sure but he didnt mention about spherical harmonics - I have also had a couple of explanations but am just trying to get as many as possible so I can do further research - so if you have time to give a full response please dont oversimplify your replies - its up to me to go and do the research afterwards and heres plenty of people here at the university that can point me in the right direction...
> > A detailed explanation would be a spherical harmonic one > ... and possibly not what you want ... > > A simplistic one is that 'W' is a sum, whereas 'X', 'Y', 'Z' are > differences. > So (ignoring any misgivings about using six capsules, and > presuming their directional sensitivities are such that this > will work, ....): > W = Xf + Xb + Yl + Yr > X = Xf - Xb > Y = Yl - Yr > (I am also ignoring normalisation, and dropping 'Z' to keep > it simple.) > ( f,b,l,r = front, back, left, right) > > So to feed a 'front' loudspeaker: > F = W + X > and a 'back' > B = W -X > or > F = 2Xf + Yl + Yr > B = 2Xb + Yl + Yr > > This is hideously over-simplified, but with all its errors > I hope it demonstrates how using a sum (W) and > differences (X,Y,..) allows reconstitution. > > For a better (accurate) appreciation, you need to tackle spherical > harmonics. > > Michael > > > > > ------------------------------ > > Message: 3 > Date: Thu, 24 May 2012 12:53:10 +0200 > From: J?rn Nettingsmeier <netti...@stackingdwarves.net> > Subject: Re: [Sursound] Why do you invert the phase of one channel of > multi capsule microphones ? > To: Surround Sound discussion group <sursound@music.vt.edu> > Message-ID: <4fbe1316.1030...@stackingdwarves.net> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > On 05/24/2012 11:57 AM, Augustine Leudar wrote: > > Hello all, > > I am building a six capsule ambisonic microphone. I have been told > > that with the opposite capsules (ie up/down, left/right, > > forward/backwards) I should invert the phase of one of the channels > > and then add them to get the X,Y,Z for the ambisonic b format. I've > > been struggling to find a good explanation - I was wondering if > > anyone could explain why this is in detail ? > > if this is not obvious to you, then i'd recommend to do some more > research before you spend lots of money on parts and lots of time on > assembling the mike. > > what you are trying to do sounds like a "native" b-format microphone, > but made from individual cardioid capsules. to get a figure-of-eight > (which has one in-phase lobe and another with inverted polarity), you > can subtract two back-to-back cardioids, which is just the same as > adding them with one of the capsules inverted. > > best, > > > j?rn > > > > > > -- > J?rn Nettingsmeier > Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487 > > Meister f?r Veranstaltungstechnik (B?hne/Studio) > Tonmeister VDT > > http://stackingdwarves.net > > > > ------------------------------ > > Message: 4 > Date: Thu, 24 May 2012 16:43:10 +0530 > From: umashankar mantravadi <umasha...@hotmail.com> > Subject: Re: [Sursound] Why do you invert the phase of one channel of > multi capsule microphones ? > To: <sursound@music.vt.edu> > Message-ID: <col122-w369ffc49bef410c956456cba...@phx.gbl> > Content-Type: text/plain; charset="iso-8859-1" > > > dear augustine > > x y and z represent three figure of eight microphones. the way to generate > a figure of eight microphone out of two opposed cardioids is to invert the > phase of one, and sum them. > > umashankar > > i have published my poems. read (or buy) at > http://stores.lulu.com/umashankar > > > > Date: Thu, 24 May 2012 10:57:35 +0100 > > From: augustineleu...@gmail.com > > To: sursound@music.vt.edu > > Subject: [Sursound] Why do you invert the phase of one channel of multi > capsule microphones ? > > > > Hello all, > > I am building a six capsule ambisonic microphone. I have been told > > that with the opposite capsules (ie up/down, left/right, > > forward/backwards) I should invert the phase of one of the channels > > and then add them to get the X,Y,Z for the ambisonic b format. I've > > been struggling to find a good explanation - I was wondering if > > anyone could explain why this is in detail ? > > _______________________________________________ > > Sursound mailing list > > Sursound@music.vt.edu > > https://mail.music.vt.edu/mailman/listinfo/sursound > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > https://mail.music.vt.edu/mailman/private/sursound/attachments/20120524/5f618a65/attachment.html > > > > > ------------------------------ > > Message: 5 > Date: Thu, 24 May 2012 07:48:02 -0500 > From: "Michael Graves" <mgra...@mstvp.com> > Subject: [Sursound] Dev-Audio MicroCone > To: "Surround Sound discussion group" <sursound@music.vt.edu> > Message-ID: > <201205241248.q4oclxjm024...@mail155c8.megamailservers.com> > Content-Type: text/plain; charset="iso-8859-1" > > Hello All, > > I'm delurking for a moment to see if anyone here has any knowledge of > Dev-Audio's Microcone? > > http://www.dev-audio.com/ > > They have some marketing language that describes it as a 3D microphone > for simple recording applications. It records four streams to their > recording application (Mac only.) > > They seem to have six capsules internall, but record four streams. > Could it be derived from something Ambisonics based? > > I've emailed them to inquire about the specifics of the microphone > capsules. > > Michael > > -- > Michael Graves > mgraves<at>mstvp.com > http://www.mgraves.org > o713-861-4005 > c713-201-1262 > sip:mjgra...@pixelpower.onsip.com > skype mjgraves > Twitter mjgraves > > > > > > ------------------------------ > > Message: 6 > Date: Thu, 24 May 2012 14:27:26 +0100 > From: "Rev Tony Newnham" <revtonynewn...@blueyonder.co.uk> > Subject: Re: [Sursound] Dev-Audio MicroCone > To: "'Surround Sound discussion group'" <sursound@music.vt.edu> > Message-ID: <004e01cd39b0$f631f970$e295ec50$@co.uk> > Content-Type: text/plain; charset="us-ascii" > > Hi > > The specs on http://www.dev-audio.com/products/microcone/ show that the > device appears to use 7 omni-capsules and some sort of "custom" DSP to > obtain the requisite 6 channels (for group discussions) from them. > > They're mraketting it for voice recording. > > Every Blessing > > Tony > > > -----Original Message----- > > From: sursound-boun...@music.vt.edu [mailto: > sursound-boun...@music.vt.edu] > On > > Behalf Of Michael Graves > > Sent: 24 May 2012 13:48 > > To: Surround Sound discussion group > > Subject: [Sursound] Dev-Audio MicroCone > > > > Hello All, > > > > I'm delurking for a moment to see if anyone here has any knowledge of > Dev- > > Audio's Microcone? > > > > http://www.dev-audio.com/ > > > > > > > > ------------------------------ > > _______________________________________________ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound > > > End of Sursound Digest, Vol 46, Issue 6 > *************************************** > -------------- next part -------------- An HTML attachment was scrubbed... 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