Does MMHR require shielded cable?

If MMHR is balanced, they will likely be configured as 4 sets of balanced twisted pairs.

What then would act as ground? I'm asking as I don't know.

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).