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4mm cable VS serious power

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msoundsystem View Drop Down
Young Croc
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    Posted: 10 June 2021 at 7:20pm
Hi guys. Il Keep it kinda short. 

Im using crown vz5000 amps in bridge mode. Yes insaine amounts of real power.., im running 25m legnths  of 4mm cable from the bridged amp into one speaker box then linked to another speaker box with a 1m link 4mm lead, making it a 4ohm load on the amp. 

My question is, would it be better to run single 4mm cables to each cab from the amp rather than using a link to get two boxes together with that amount of power? I can link the 2x 4mm cables at the amp end... 

It just had me thinking it may be the weakest link in the chain considering i give my amps a propper 32a stiff supply, soon to be upgraded to 63a 3phase. 

The subs move your organs and break your teeth. So there is nothing wrong, just thinking of upgrading the cable side of things.


Cheers 


Edited by msoundsystem - 10 June 2021 at 8:15pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billso Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2021 at 7:36pm
Yes of course doubling up your cable from 4mm to 8mm is going to be better.
Is it worth it ? Well that really depends on the length of the runs.
Remember 5m of 2.5mm will be better that 10m of 4mm.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote msoundsystem Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2021 at 8:14pm
Forgot to say i use 25m legnths! 

Didnt know if it was worth it hence the question...
I guess more can't hurt 😉
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billso Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2021 at 8:31pm
With cables that long at I would definitely double them at the very least.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2021 at 9:15pm
Move the amps nearer the speakers?

And regarding the mains, if you are not taking out breakers at 32A, it wont get any louder at 63/3...
“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
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Post Options Post Options   Thanks (0) Thanks(0)   Quote msoundsystem Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2021 at 9:18pm
Reason for distro upgrade is i have popped breaker 

I will have  x12 vz5000 in bridge next summer so it will be needed.
I need the 25m for what  i do. I do have shorter lengths but im talking about the long runs..

Will double up cable, instead of linking cabs il send separate 4mm to each cab from one amp..

Thanks 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Contour Quote  Post ReplyReply Direct Link To This Post Posted: 11 June 2021 at 10:10am
As stated above, place amplifier closer to the speaker. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 11 June 2021 at 11:12am
That's a hell of a lot of extra copper to carry. Are your cables already 4-core? If so then why not just make a pin-flip cable to act as the 1-metre link between boxes?

That way each box is getting a 4 mm pair, just the same as running a second 2-core connection, but you're transporting, uncoiling and recoiling less stuff in the mud each show.

If you really, really want to maximise the CSA, then you can use 4x 4 mm to each box and join the cores inside the cabinet and amp end to have an effective 2x 8 mm each run.

But it's up to you, because right now you're losing no more than -0.24 dB to a 25 metre 4mm cable run (based on 4.36 Ω/km resistance). More of that will be lost as the drivers get warm...

The maths, if you'd like to check the difference for yourself:


Where d is the decibel loss, L is the cable length, r is the cable resistance per km, and z is the loudspeaker nominal impedance.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 11 June 2021 at 2:25pm
if you a really lugging around 6*25m of 4*4mm just to power your subs you should really think about getting several smaller amp racks and some XLRs to link them together
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Post Options Post Options   Thanks (0) Thanks(0)   Quote msoundsystem Quote  Post ReplyReply Direct Link To This Post Posted: 11 June 2021 at 6:19pm
They are 2 core 4mm cable! Not 4 core.. the reason for single 2 core cables is i can change stack configuration as needed for the event. My tops are bi amped 4 core thats ok no issue there.. 

My amps are individually cased so stack as many as i need for the show, 
Im aware im not losing alot. But iv spent so much on the system i want to upgrade the cables,  i have an army of 2x4mm cables so thats no issue. 

I have full crew and all cables in cable trunk so no issue. Cable weight is nothing compared to the stack.. 

All il do is run individual 2 core 4mm cable to each box rather than 2 box on one cable. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 11 June 2021 at 8:23pm
I’m not really sure how using two core cables benefits changing your stack configuration, since using four core everywhere would be way more flexible but each to their own.

At best, your ‘upgrade’ will give a 0.1 dB boost. In total. It’s way, way below the just noticeable difference for volume level change.

Edited by toastyghost - 11 June 2021 at 8:23pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aman Gebru Quote  Post ReplyReply Direct Link To This Post Posted: 12 June 2021 at 4:11pm
Your problem is damping factor and power handling of the cable.

The total system damping factor of a VZ5000 driven 2 ohms per channel on a single 4mm2 cable will be 19, which is ridiculously low. I wouldn't even go near an amp/speaker combo with a damping factor of less than 50, and ideally 100.

Even if you doubled up the 4mm2 cable DF would only get to around 34.

Power reaching the speaker on a single run of 4mm2 would be 4504 watts, so you've lost 500 watts.

Max power handling for the single cable would be 1600 watts.

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