Porous lead magnesium niobate-lead titanate (PMN-PT 90:10) relaxors were impregnated with water to provide a model conductor-insulator mixture, to study their power law frequency dependency of ac conductivity, permittivity and phase angle. Relaxor materials with a range of open porosity filled with water created composites with conductor volume fractions ranging from 8.2% to 22.2%. The use of a high relative permittivity PMN-PT ( 8000) enabled the power law dispersion to be observed at relatively low frequencies ( 2 kHz). Good agreement was obtained between experimental data and predicted results based on a logarithmic mixing rule with a strong correlation between the power law exponent and conductor-insulator fraction. The model and numerical methods presented are considered a simple approach to interpret and predict and the frequency dependent properties of materials which similar heterogeneity.