> 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 ?
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 _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
