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Bass Speaker Wire issue

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taurusty View Drop Down
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    Posted: 24 February 2017 at 1:20pm
Lost a RAM BUX 2.0 over the weekend over what I assume is as shorting 40' 4 core 2.5mm spkr cable that has NL 4's at each end. fault light was on at the time with gentle clip light activity.

On returning to base checked the cable with a Neutrik tester; all 4 terminations good. Removed both NL 4's and metered the wires individually against each of the other 3 and no shorts detected.

Replaced NL 4's with BNIB units and tried again, on a Crown iTech 6000, clip lights on both channels come on when turned up moderately, it even tripped a relay within.

Have visually inspected the sheath from one end to other, nothing amiss externally.



Any ideas?

Edited by taurusty - 24 February 2017 at 1:23pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2017 at 1:31pm
arcing at the nl4 terminals? 2.5mm on those terminals is a bit iffy especially if you have another parallel connection off it as well. I solder and put a big blob of of silicone around the terminals and wires.
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taurusty View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote taurusty Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2017 at 1:34pm
I had changed the NL4's for brand new ones.
Is it possible the insulation in the cable is breaking down at higher power levels?
Personally, have never seen that but at a real loss this time...

I have three cables of the same guage; 1 longer, other same length. Have been using them maybe 3 times a year for the past 7, this is the 1st I've encountered this...

Edited by taurusty - 24 February 2017 at 1:36pm
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odc04r View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2017 at 1:49pm
When you have 4 wires, there are 4! (4x3x2x1) = 12 potential pairs of wire combinations to fault between. Did you measure every single possible pair combination or did you just do 1-1, 1-2, 1-3, 1-4?

It is possible that a voltage being present is exacerbating a breakdown, but I find it unlikely.

Internal faults in cables can be some of the hardest to detect and find reliably. Sometimes the cable needs to be coiled in a certain place etc to make them known.

Edit, I am a dumbass and there are actually 6 total pair combinations to check. Make sure you've done them all before you start looking at more complex causes. Also test with the cable coiled and uncoiled, and perhaps make a continiuity test from same pin at each end of the cable when coiled and uncoiled. Higher resistance here could mean damage in one wire and that might cause localised heated in the cable under use and upset it further

If all else fails, you could hire a HV tester and see where the insulation breaks down between pairs of cables. One capable of a few hundred V in 10V steps should do nicely. Usual warnings apply, don't put it on your tongue or testicles etc. Use your mates instead.


Edited by odc04r - 24 February 2017 at 2:01pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BJtheDJ Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2017 at 2:01pm
Originally posted by taurusty taurusty wrote:

Lost a RAM BUX 2.0 over the weekend over what I assume is as shorting 40' 4 core 2.5mm spkr cable that has NL 4's at each end. fault light was on at the time with gentle clip light activity.

On returning to base checked the cable with a Neutrik tester; all 4 terminations good. Removed both NL 4's and metered the wires individually against each of the other 3 and no shorts detected.

Replaced NL 4's with BNIB units and tried again, on a Crown iTech 6000, clip lights on both channels come on when turned up moderately, it even tripped a relay within.

Have visually inspected the sheath from one end to other, nothing amiss externally.
Any ideas?


Were you clipping the amps with the cable plugged into the speakers??  Did you try connecting the cable to the amp and running without having speakers plugged in ??

The fault may lie inside a speakerbox.

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taurusty View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote taurusty Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2017 at 3:08pm
yes ODC04r, checked each wire against the rest w a tester for continuity, not resistance. All these tests are done with the cable only, no spkrs boxes or other cables attached to the test amp as I narrowed it down fr the venue. I even changed around the pairs ( fr red/ Blk to Grn/wht, then grn/red etc) with no change in the amp behavior. I'm thinking bin it!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote BJtheDJ Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2017 at 3:15pm
Originally posted by odc04r odc04r wrote:

Usual warnings apply, don't put it on your tongue or testicles etc. Use your mates instead.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote cravings Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2017 at 3:26pm
why are you so sure the problem was with the cable?

have you tried the amp since the gig?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dylan-penguinmedia Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2017 at 4:10pm
Do you have a mate who's an electrician? Borrow an insulation resistance tester and use that to see if it's the cable.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2017 at 5:23pm
Originally posted by dylan-penguinmedia dylan-penguinmedia wrote:

Do you have a mate who's an electrician? Borrow an insulation resistance tester and use that to see if it's the cable.


You can pick up an insulation tester for silly money these days:

http://www.ebay.com/itm/BM500A-Digital-Insulation-Resistance-1999M-1000V-Tester-Meter-Megohmmeter-Nice-/381235442908?hash=item58c36734dc:g:J-QAAOSw5VFWHbRm


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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2017 at 8:34pm
Gut feeling would be that the cable is fine and there cause of the fault was somewhere else.

Why do you think it was a cable fault?

Edit: ok, could be a cable manufacturing fault. Have you tried using the cable tester and working your way down the cable, flexing it as you go? If there is an insulation fault you might be able to stimulate it.

Edited by ceharden - 24 February 2017 at 8:37pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shagnasty Quote  Post ReplyReply Direct Link To This Post Posted: 25 February 2017 at 5:32am
In real terms, speaker leads don't "break-down" under voltages an amp can produce let alone "arc over" unless you have mashed section of lead (which you have ruled out) I would be looking elsewhere for faults (like in the cabs for "fastons" and other non-PA related junk!
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