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Suggestions for earthing EAW crossover

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Requiem View Drop Down
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    Posted: 11 July 2021 at 2:24pm
Hi guys, looking for suggestions on the best way to earth a load of mid-tops,

Basically they are EAW KF750PX de-installed from Wembley stadium and whilst renovating them I removed the Socoplex connector on the back and wired them to run bi-amp on an NL4 (the mid & HF are on a passive x-over).

So there are 3 cables going into the passive crossover, the positive, neutral and earth..
Ive already installed and wired up the NL4 inputs  and I have a trailing cable inside the cab ready to attach to an earth point ,

Been looking online for suitable bits to use but not coming up with much, I'm wanting something like a push connector as these are being retrofitted from install to touring cabs, dont fancy having to screw a cable on each time, was going to drill through and attach the earth point next to where the NL4's are, but cant seem to find much that seems suitable, basically looking for a singular heavy duty push terminal or something like that... google / ebay isnt helping much

any suggestions / links appreciated!

EDIT: On completion I was planning to link the earths on all cabs then down to a ground stake for outdoor events or wired to the earth terminal on a household plug and plug it in for indoor events (testing the plug beforehand with a plug tester to make sure the ground is ok), can anyone see an issue with this? Never had to ground a passive cab before!

Edited by Requiem - 11 July 2021 at 2:27pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote VECTORDJ Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2021 at 3:04pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2021 at 3:44pm
Cut the ground wires off the crossover and forget about it, NOBODY earth grounds a passive speaker and doing so outside a fixed install application will cause more problems than it cures.

Second thought. Are you sure that is a ground and not a sense line for the UX processor?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Requiem Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2021 at 12:02pm
Originally posted by Conanski Conanski wrote:

Cut the ground wires off the crossover and forget about it, NOBODY earth grounds a passive speaker and doing so outside a fixed install application will cause more problems than it cures.

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


That was my original plan, but the cabs sound real dodgy without the earth connected, and EAW have stated they need to be earthed. 

Have studied the wiring diagrams from EAW and it is 100% an earth. I cant post them on here though as had to sign an NDA to receive them.

These were one-off builds for wembley stadium, not the production model.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2021 at 1:21pm
If the ground is required as some part of a return circuit can you not ground them back to the amp rack? This should be earthed.

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.

 



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Post Options Post Options   Thanks (0) Thanks(0)   Quote fat_brstd Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2021 at 1:33pm
Can you bin off the crossover entirely and just go 3 way active? Sounds like an easier way to go about it as you should be able to get rid of the earth.

I've never heard of a box that needed to be grounded for a crossover to work. As above I would have thought sense wires and some bullshit proprietary controller but I'm still not sure exactly how the earth could work.

Any chance its something to do with 100V line runs or the drivers are a weird high impedance so they can daisy chain lots of them?

I really want more info on these boxes

Edited by fat_brstd - 12 July 2021 at 1:38pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tinnitus Rex Quote  Post ReplyReply Direct Link To This Post Posted: 12 July 2021 at 3:19pm
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.


Edited by Tinnitus Rex - 13 July 2021 at 8:54pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 13 July 2021 at 2:09pm
Hrrmmmm, without those wiring diagrams this is a difficult problem to solve...Have you tried linking the earth to the negative line to see what happens? 
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smoore Quote  Post ReplyReply Direct Link To This Post Posted: 13 July 2021 at 7:35pm
Freddy, I got 4 of the same cabs from Ollie with the same passive X-over inside and they sound fine without any extra grounding? I can't remember if I read it or worked out that the extra signal cable going into the IP connectors is an over-ride signal / alarm / emergency thing they needed for when there was a fire or some such thing in the stadium..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smoore Quote  Post ReplyReply Direct Link To This Post Posted: 13 July 2021 at 7:42pm
Here we go. I wired NL4's into mine and just run the 12"s in parallel. The yellow cable was just left wrapped in tape. They sound great!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote DJ-Dulux Quote  Post ReplyReply Direct Link To This Post Posted: 14 July 2021 at 7:37am
A voice evacuation system would be present in the venue most likely, Pin 7 will be the way the Mid / high drivers are monitored to ensure its working. We used to have units that sent 20kHz test signal around the drivers, if it dropped the system would fault. This looks like an alternative to that.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Requiem Quote  Post ReplyReply Direct Link To This Post Posted: 14 July 2021 at 12:08pm
Originally posted by smoore smoore wrote:

Here we go. I wired NL4's into mine and just run the 12"s in parallel. The yellow cable was just left wrapped in tape. They sound great!



Yeah I binned these panels haha, so the yellow cable was the earth and the white cable is the neutral for the x-over? Are you sure? This might be where I'm muddling things up, I was using the yellow cable as the neutral and leaving the white cable off thinking it was ground, 

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..
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