Exciters are also used to synthesize harmonics of low frequency signals to simulate deep bass in smaller speakers.
Originally made in valve (tube) based equipment, they are now implemented as part of a digital signal processor, often trying to emulate analogue exciters.
The aural exciter adds phase shift and musically related synthesized harmonics to audio signals.
Aphex released in 2001[1] the Model 204 Aural Exciter and Optical Big Bottom, yet another refinement of the original unit.
The BBE Sonic Maximiser uses a similar process of frequency-dependent phase shifting, as do other brands to a varying extent.