Running 2 audio lines with a shared ground

[calforhelp]

I am making a multi pin interface with a 8 pin Neutrik Speakon connector. The problem I am having is that I have 5 things to run through it (10 wires).

-12vdc .5A power
-Incoming mono line level from Mac
-Incoming mic level microphone
-Outgoing mono audio to one 8W monitor speaker
-Outgoing mono audio to another 8W monitor speaker

The two monitor speakers are going to have individually controlled volume at their separate amps.

So is there any way some of these lines of audio can share a negative contact? I need to turn their 10 leads into 8 somehow.

Thanks guys!

[JohnRoberts]

I'd be nervous... sound quality and maybe even stability if speakers and mic talk to each other...

[LeeYoo]

+1
Maybe the speakers can share a common ground pin.
And the mic/line shield on a shared pin.

[Matt Syson]

Hi
I would count this as 11 lines anyway as the mic level must be treated as balanced if you don't want it to oscillate.
Presumably you are making this cable up as a 'composite' snake as you cannot use a bit of old multicore you have lying around.
There are many ways this is a bad idea.
boosting and balancing the line and mic signals 'at source' and sending them at low impedance balanced stands some chance of wirking but again you need a 'composite' cable.
Having a common ground for the 2 speakers is 'OK' (as long as the amplifier is happy) but will crosstalk a bit, depending on cable length and resistance.
Matt S