Mechanical energy harvesters ensure an important electromechanical coupling when their natural frequency matches the input frequency. Nevertheless, in many situations the driving frequency is not known or it might change over time. In that case, the output power falls dramatically when the input frequency is not equal to the natural frequency of the harvester. It would be more advantageous to design a system able to operate over a wide bandwidth. The aim of our work is to broaden the peak resonance of the resonator. We propose to do this by introducing an additional process allowing more transfer of mechanical energy from the source to the converter. The amplification of the transferred energy ensured by this process is achieved by gathering the resonance phenomenon conditions.