In this paper, the effective radiation area (Sd) is obtained (theoretically and experimentally) for different loudspeakers. For this purpose, is considered a near field approach. This method is theoretically based in previous works that use the geometrical properties of different axisymmetric pistons and calculate the effective radiation area by positioning the pistons in an infinite baffle. In the case of loudspeakers, the calculations are redefined with the new geometrical conditions, in order to increase the precision of the results. Finally, these results are compared with the listed effective radiation area of the loudspeakers data sheets, and other techniques, in order to set the accuracy of the measurement.