``Mario Schenberg'' is a spherical resonant-mass gravitational wave (GW) detector that is expected to be part of a GW detection array of two detectors. Another one is been built in The Netherlands. Their resonant frequencies will be around 3 kHz with a bandwidth of about 200 Hz. This range of frequencies is new in a field where the typical frequencies lay below 1 kHz, making the transducer development much more complex. Some studies indicated that the use of low mass mechanical resonators (used for impedance matching to the parametric transducer, in a cold damping regime) allows the detector to reach the standard quantum limit. In this work we describe the study of a new shape for the impedance matching resonator used to obtain a better coupling between the sphere and the transducers and a better use of the space inside the experimental chamber.