On Mon, Apr 25, 2011 at 04:24:36PM -0400, Lee Byrd wrote: > Can anyone enlighten me or point me to materials which explain the workings > of the Dominance control variable in first order ambisionics decoding? > > I have a decent conceptual understanding of the matrixies involved in > soundfield rotations and the derivation of virtual microphone patterns and > vectors, as well as emprical experience with the use and practical limits of > the Dominance variable as realized in the 'Zoom' control function in VVMic > for Tetramic. However I'm looking for a deeper understanding of what the > Dominance control is doing.
The basic idea is to modify W into a directional pattern rather than an omni, and adjust the others to match. Using standard encoding (i.e. W is 3dB below X for a forward source), dominance in the forward X direction means: W' = W + (a / m) * X X' = X + (a * m) * W Y' = b * Y Z' = b * Z with m = sqrt(2), a in the range [0..1] and b = sqrt(1 - a^2) This preserves the relation between the gains 2 * W^2 = X^2 + Y^2 + Z^2 on the modified encoding W',X',Y',Z'. The result is somewhat contradictory: for a > 0 gain in the forward direction is increased (as if the mic were closer), but at the same time the image becomes narrower (as if the mic were more distant). In the limit case a = 1 both W and X become a forward facing cardioid, Y and Z are zero, and everything collapses into the forward X direction. For any other direction, first rotate so the dominance direction becomes X, apply the transformation, rotate back. Ciao, -- FA _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound
