I know DSP's are available for loudspeaker frequency response
compensation, typically combined with a non-time-coherent "room
correction" function.

Is anything similar available for treating loudspeaker distortion?
(actually whole-of-system distortion, but measured as what comes out
of the speaker and hopefully dominated by the speaker's distortion
contribution).

I don't mean a research tool for speaker designers. I mean something
that can be used in the home or studio to reduce distortion from
existing systems.

Stand-alone or PC-based.

I imagine something that fits in the audio chain between the sound
source and the amplifier. It might generate its own test signals and
analyse the speaker output through a microphone. It could treat
harmonic distortion by mapping a number of harmonics of measured
distortion against signal amplitude against signal frequency. It could
then generate a compensating map of out-of-phase harmonics. Then when
playing music through the system, it could apply the compensating map
real-time to the incoming music signal.

Of course it would be sensible to combine such a function in the same
DSP as is used for frequency response compensation.

Am I dreaming, or describing a real product?

Grant