the idea is to run an eight-way symmetric audio
multicore (shielded
pairs and an outer foil shield as well) along with 4x cat5 s/stp
cables carrying 10/100/1000baseTX ethernet in the same cable duct
over a length of about 15-20 meters.
The only thing I'd have to add is that multicore is not actually
designed to be used with microphones and mixers - it's a bit flimsy
for that, as an XLR plug is designed for a much fatter individual
cables. It's actually designed for those rectangular multiway plugs
with lots of pins.
If I was rebuilding my studio from scratch, I'd use full sized cable
with braided shielding for all the looms. (The multicore was already
installed by the time I moved in). It might need bigger ducting, but
I suspect the interference rejection once the loom has been split
into individual wires would be much greater.
You don't need to have the wires outside of the outer shielding with a
multiway plug, but if you have a mixer with XLRs or a patch panel...
Cheers
Daniel