Numerical and physical modelling of heterogeneous magnetic media in the quasistatic range (where eddy currents have to be taken into account) show that an Effective Medium Theory devoted to the description of these materials is pertaining to the behaviour of an effective particle, size of which is a function of the load in magnetic matter. The particles clustering in the whole concentration range (including the constitution of a conducting path throughout the actual material) seems to be quite well accounted for by this EMT.