The interpenetrating three fluid models are presented to study the composition dependence of the sound velocity, diffusion coefficient and ionic conductivity in the liquid Ag-Cu-Se system. The model predicts that the sound velocity exhibits an extremal value at intermediate cationic composition. It is also shown that the obtained behavior of the ionic conductivity agrees qualitatively with that observed experimentally in the superionic: phase. (C) 2008 Elsevier B.V. All rights reserved.