Exciter is also known as bodyshaker, Audio Exciter is just basically a loud speaker without a membrane, and it consists of voice coil , oscillating mass and mounting ring/plate. If the audio/music signal is applied to the contact pins of the voice coil, the oscillating mass starts shaking with the frequency of the applied music, the oscillation is transmitted to the mounting ring and from there on to the surface the exciter sticks to, thus the excited surface emits the music signal.
For testing the audio exciter I did built a small opamp based amplifier which delivers 2Watts rms at 6ohms impedance
This amplifier circuit is nothing new. and you can find a better one here (discrete transistor amp)