Dual Speaker Cable Runs

[citizenX]

I've never done this but heard some folks talking about it for higher-power applications...might be the pro-industry standard but what do I know. FYI my sub runs are 12 gauge with speakons, less than 40'.

Live sound......when needing to couple two sub boxes together to run off one side of an amp, would it be better to run two separate cables from the amp channel or just the traditional one cable with a short daisy-chain jumper at the boxes? Seems like the dual cable method would mean double the effective wire gauge but not sure how critical/beneficial this would be for a shorter 12 gauge run.

[Sydney]

Re: Dual Speaker Cable Runs

Distro with individuals runs is what I've seen.

[citizenX]

Re: Dual Speaker Cable Runs

Yeah I guess I've seen that too now that I think about but still wasn't sure if they were daisy-chaining at the other end. What about for shorter runs though, you think it makes much difference for say 25'?

[Sydney]

Re: Dual Speaker Cable Runs

Not much of a difference:
"Our" reasons for "home runs" was clarity of setup and flexibility.
All cables were long to allow for the widely varying layout requirements - running behind and around objects gobbles up length.

[billfitzmaurice]

Re: Dual Speaker Cable Runs

Seems like the dual cable method would mean double the effective wire gauge but not sure how critical/beneficial this would be for a shorter 12 gauge run.

Use this to figure out the gauge you need. If a single 12ga is adequate then there's no reason not to run just one to the first sub and daisy chain to the second.

http://www.bcae1.com/images/swfs/speakerwireselectorassistant.swf

[citizenX]

Re: Dual Speaker Cable Runs

Use this to figure out the gauge you need. If a single 12ga is adequate then there's no reason not to run just one to the first sub and daisy chain to the second.
http://www.bcae1.com/images/swfs/spe...rassistant.swf

Thanks that's a cool resource but I have a question. My run is 50' on a 12 gauge wire with 2500 watts @4 ohms (two 8ohm subs daisy-chained). The calculator says the decibel loss is ok inaudible @ .34 for my given run but the 300 circular mils per amp thing says my wire is too small? If I instead run two 12 gauge lines 50' at 1250 watts each at 8 ohms (one line to each sub) then the 300 circular mils thing goes away and of course the db loss drops to .17

What is the 300 circular mils per amp thing and is that really even a factor if my db loss only .34 to begin with? Is a single 12 gauge line then not adequate for this run?

[billfitzmaurice]

Re: Dual Speaker Cable Runs

What is the 300 circular mils per amp thing

That is current capacity. It indicates the wire could overheat. However, this assumes that your subs can actually handle 2500 watts. Chances are they cannot. What is their displacement limited power handling? That's what matters, not thermal. Also, even if they can handle 2500w I doubt you're actually running them at 2500w constant power, 250w with 10dB peaks is more likely.

[Sydney]

Re: Dual Speaker Cable Runs

...What is the 300 circular mils per amp thing and is that really even a factor ...

It is analogous to cross sectional area.
In Electronic intro - the analogy is often water flow. With current ( amperage ) being flow volume.
So like a pipe - increased cross-sectional area has less friction loss and allows more flow.
In industrial electronics the loss can be calculated as a percentage and determinations made on acceptable voltage drop.
For example:

http://www.genuinedealz.com/voltage-drop-calculator

[citizenX]

Re: Dual Speaker Cable Runs

Thanks guys. The drivers are rated at 1000rms/2000peak per so they can take some power. My new sub amp is pretty beefy wattage wise 2500/4ohm per channel but that's a 1k rating so real power is obviously much lower and obviously not continuous so I think I'll stick with the single 12 gauge line for this weekend and see how it goes. Might do an A/B comparison with single/dual runs and see if it makes any audible difference.

[billfitzmaurice]

Re: Dual Speaker Cable Runs

Thanks guys. The drivers are rated at 1000rms/2000peak per so they can take some power.

That's thermal. When you modeled the driver/enclosure what was the maximum power? WinISD Pro for one calculates that using the Pe rating and maximum excursion, whichever is less. And that is what you should be using to determine the voltage for limiting and power for cable requirements.

[Sydney]

Re: Dual Speaker Cable Runs

...The drivers are rated at 1000rms/2000peak per so they can take some power. ,,,

Remember that as more power is applied to the relatively small VC wire - the more heat is generated.
Those power levels are reserved for very brief peaks, not continuous duty cycle.
The more the voice coil temperature rises, the greater is the reduction in sound output
See page 74 of Loudspeaker and Headphone Handbook edited by John Borwick
page 453 of Sound Reproduction: Loudspeakers and Rooms By Floyd E. Toole
page 122 of Audio Engineering for Sound Reinforcement By John Eargle, Chris Foreman
And
Heat Dissipation and Power Compression in Loudspeakers by Douglas J. Button

[citizenX]

Re: Dual Speaker Cable Runs

That's thermal. When you modeled the driver/enclosure what was the maximum power? WinISD Pro for one calculates that using the Pe rating and maximum excursion, whichever is less. And that is what you should be using to determine the voltage for limiting and power for cable requirements.

Well, I was using WinISD beta so it didn't show me as much data as Pro does. I have since installed WinISD Pro and using the same modeling, if I am interpreting things correctly, I can drive my subs up to 800 watts (single 8ohm sub) before I hit full Xmax (10mm) around 55hz. That said, according to that wire calculator, a single 50' 12 gauge line is more than adequate @ 4 ohms (daisy-chaining two subs) even considering the higher output from the amp. Looks like I'm good, Again, that is if I am interpreting the data correctly.