Second thought. Are you sure that is a ground and not a sense line for the UX processor?

As to how to physically do this, the obvious way is through a multicore, maybe time to restore the socapex connectors which will obviously have enough available contacts.

 

Electricly "Earth" is a term used to describe a low resistance path of equal potential as "neutral" vs "live"  ,basically neutral and earth are the same thing.

In passive speakers there is no such situation , there is just positive and negative.

"Grounding" anything such as a hifi ,a generator or even a stage with a spike into the earth can create all sorts of unforseen effects too numerous to go into here.(see excellent and scarry generator thread)

 The negative speaker outputs of most "single ended"amplifiers are already connected to chassis earth/ground .  IF you ground/earth  any part of your  crossover and use a bridged amplifier (one that uses both possitive terminals and some amps are internally bridged these days)  you will have a VERY unhappy amplifier.(a direct short to zero volt of the PSU)

Im pretty certain if  your speaker sounds different then its not wired up correctly reguardless of "ground" ,"earth" or whatever were calling "it"here.

As Tinnitus Rex says, on most conventional amps that aren't in bridge mode the negative terminal is the power supply return/ground which is often (or can be) linked to mains/chassis earth. Sometimes there is a small value resistor between mains earth and the chassis - if you try to return a lot of current through that, it is likely to evaporate.

I can not for the life of me imagine why they would make the wiring more complicated than it needs to be. I would imagine the crossover could be modified to eliminate the earth wire and make it like a stock KF750.

Dupe...

Ill try switching them over, I've been having a right nightmare with it, I did the same as you and linked the 12"s together to make a 4 ohm cab and then ran them on the +1/-1 of the NL4, and then linked what I thought was the +/- of the x-over to the +2/-2 of the NL4...

So with the black and the yellow of the x-over connected the speakers seem really muffled and the HF seems to be coming from the mid driver which isnt right, and when I was trying to sort it out I put the white into the same terminal on the nl4 as the yellow to see what would happen and then seemed to get a tonne of HF out of the HF driver but absolutely no mid from the 10", when I put the white onto the same terminal as the black I got nothing, so after looking at the wiring diagrams I thought it must be an earth problem, ill try swapping over and leaving the yellow unconnected and see how I get on..

I think the best thing you could do is not use the words "live, neutral and earth" at all when working on or discussing a passive speaker.

The panel clearly says "monitor"on pin 7 , why are you calling it "earth"? your just confusing yourself and others.

I suspect you should ignore the diagram, I actually wrote down the wiring colours I used but I'm 200 miles away from the boxes and can't confirm whether this is wiring I attached or wiring from the box. I think its the wiring already in there as we have Yellow. I also did some tests to check I had the correct phases but I can't remember what. Anyway -> 

Good advice, brain wasn't functioning correctly after stressing out about the whole thing for a fairly long period of time, and getting lots of different people tell me very different things!