Subwoofer cable question. - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 25 Old 04-11-2017, 07:07 AM - Thread Starter
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Subwoofer cable question.

I am trying to move the subwoofer to the back of the room and planning on dragging cable through a conduit under the house from the receiver up front. My question is for sub cable, can I run plain 16g speaker cable as I will for the rear speakers, and cap it with RCA plugs, or should I just buy a 25-30ft sub cable and run that?

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post #2 of 25 Old 04-11-2017, 07:33 AM
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I would buy a rca cable. Plain speaker wire is not shielded and my allow other sounds to leak in.

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post #3 of 25 Old 04-11-2017, 07:38 AM
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Unbalanced cable is good for 15-20ft runs. If your AVR/sub have the proper connections, run balanced lines instead to avoid the possibility of coupled noise.

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post #4 of 25 Old 04-11-2017, 07:47 AM
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post #5 of 25 Old 04-11-2017, 07:50 AM
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^^^ I'd probably splurge for the $7 CL-2 version in this application. https://www.monoprice.com/product?c_...seq=1&format=2

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post #6 of 25 Old 04-11-2017, 09:00 AM
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An XLR balanced interconnect system is often a better choice than RCA unbalanced interconnects.
But it's seldom available. So for long RCA interconnects the best choice is the Blue Jeans Cable LC-1.

http://www.bluejeanscable.com/store/subwoofer/index.htm

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post #7 of 25 Old 04-11-2017, 09:43 AM
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What does balanced/ unbalanced cable mean? Do I need to pay attention to this for a 10-15 ft run under a rug?
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post #8 of 25 Old 04-11-2017, 09:58 AM
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Originally Posted by VizYamaha View Post
What does balanced/ unbalanced cable mean? Do I need to pay attention to this for a 10-15 ft run under a rug?
Just do a search, balanced vs. unbalanced audio for explanations. Balanced cables have superior noise rejection from interference or grounding issues.

But no, you likely don't need to worry about this for your situation unless you're getting unwanted noise or hum on your sub - in which case if your receiver and sub have balanced (XLR) connections, you could try that as a possible fix.

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post #9 of 25 Old 04-11-2017, 10:02 AM
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One thing you might want to try now is to get an extension cord for the power cable and plug it in at the back where you plan to set the sub. If it creates a ground loop it might be nice to know now so you can order a signal power power line isolator and have it ready.

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post #10 of 25 Old 04-11-2017, 10:02 AM
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Originally Posted by 1_sufferin_mind View Post
Unbalanced cable is good for 15-20ft runs. If your AVR/sub have the proper connections, run balanced lines instead to avoid the possibility of coupled noise.
Within the subwoofer pass band there's no reason to run balanced with less than 100 foot runs, minimum. There's also the matter of not being able to use balanced cable if the AVR doesn't have a balanced line driver and the sub doesn't have balanced input. If they do I'd go balanced, on the basis that it might not help, but can't hurt. But if they don't I wouldn't be concerned.
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post #11 of 25 Old 04-11-2017, 10:45 AM
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Quote:
Originally Posted by 1_sufferin_mind View Post
Unbalanced cable is good for 15-20ft runs. If your AVR/sub have the proper connections,...
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Originally Posted by Bill Fitzmaurice View Post
There's also the matter of not being able to use balanced cable if the AVR doesn't have a balanced line driver and the sub doesn't have balanced input
Guess I shouldn't have buried that bit of info.

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post #12 of 25 Old 04-11-2017, 11:08 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
Within the subwoofer pass band there's no reason to run balanced with less than 100 foot runs, minimum. There's also the matter of not being able to use balanced cable if the AVR doesn't have a balanced line driver and the sub doesn't have balanced input. If they do I'd go balanced, on the basis that it might not help, but can't hurt. But if they don't I wouldn't be concerned.
100 feet!!! , I can put subs in my neighbors house.
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post #13 of 25 Old 04-11-2017, 01:57 PM - Thread Starter
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Thanks everyone. Appreciate the responses.

A long (25 foot) sub cable seems cheap enough that I should not have to worry about it. I will try the long extension cord to make sure there are no ground loops though.
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post #14 of 25 Old 04-11-2017, 05:11 PM
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With balanced cables it's not just the cables, it's a complete balanced interconnect system.

Balanced output stage >> balanced cable >> balanced input stage.
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post #15 of 25 Old 04-11-2017, 05:19 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
Within the subwoofer pass band there's no reason to run balanced with less than 100 foot runs, minimum.
Well there is a big problem with long unbalanced cable runs. In thise case long is well over 20 feet and it's worse if 2 AC circuits are involved. It's not about the audio signal it's self, it's about background noise due to common impedance coupling. Long RCA cables require a coax with a heavy braided shield (see my earlier post).

Quote:
There's also the matter of not being able to use balanced cable if the AVR doesn't have a balanced line driver and the sub doesn't have balanced input. If they do I'd go balanced, on the basis that it might not help, but can't hurt. But if they don't I wouldn't be concerned.
Yep!
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post #16 of 25 Old 04-11-2017, 06:07 PM
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Originally Posted by Speedskater View Post
Well there is a big problem with long unbalanced cable runs. In thise case long is well over 20 feet and it's worse if 2 AC circuits are involved. It's not about the audio signal it's self, it's about background noise due to common impedance coupling.
If what you're getting at is ground loop noise then you're correct, the longer the wire the greater the noise potential, while balanced connections properly done eliminate the possibility of a ground loop. That's why I recommend against the use of on-board amps with subs, keeping all of the electronics in one place.

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post #17 of 25 Old 04-15-2017, 12:34 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
If what you're getting at is ground loop noise then you're correct, the longer the wire the greater the noise potential, while balanced connections properly done eliminate the possibility of a ground loop. That's why I recommend against the use of on-board amps with subs, keeping all of the electronics in one place.
Agreed but there's an equally opposing argument. Sub woofers eat a lot of power. So you need heavy speaker wire to go the distance. Also it's also just not practical to put a 300watt sub woofer amp in an average AV receiver.

Me? I run balanced to a pro Yamaha 350wpc amp up by the subs. Then 10-15 foot #10s to each sub.
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post #18 of 25 Old 04-16-2017, 06:52 PM
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Agreed but there's an equally opposing argument. Sub woofers eat a lot of power. So you need heavy speaker wire to go the distance.
It would be the very rare occasion that more than 14 gauge wire is required. I've never used 10 gauge for anything, including stadium sized pro-sound systems. That's because in a pro-sound system the amps should be placed close to the speakers, because pro-sound uses all balanced connections that remove ground loop noise as a consideration. But we're not talking about a pro-sound system here.
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Also it's also just not practical to put a 300watt sub woofer amp in an average AV receiver.
It's not all that difficult to put it on the same shelf.

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post #19 of 25 Old 04-16-2017, 07:10 PM
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I have 0 gauge in my car, only downside I see is the cost. so if cost isnt a factor? who the freak cares about 10 gauge vs 14 gauge? whats the price diff again? 5 cents a foot or something?

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post #20 of 25 Old 04-17-2017, 04:26 PM
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With long loudspeaker cables, it's not a question of audio power, even a 16 or 18AWG can handle with the current. It's a question of cable end-to-end resistance with respect to the loudspeaker's impedance curve.

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post #21 of 25 Old 04-17-2017, 06:57 PM
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A 16 ga. cable is only good for 8.5 amperes, an 18 ga. 5.5 amperes, irrespective of length. Both current capacity and resistance must be considered.

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post #22 of 25 Old 04-17-2017, 07:23 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
A 16 ga. cable is only good for 8.5 amperes, an 18 ga. 5.5 amperes, irrespective of length. Both current capacity and resistance must be considered.
What spec are you referencing for those #s?

NEC's NFPA 70 says 3.7 amps, but that's multiple conductors in a wall, raceway, plenum, etc and not open air. If you've only got two conductors in open air, 1 Watt/meter dissipation for AWG #16 would be around 16 amps...?

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post #23 of 25 Old 04-18-2017, 05:28 AM
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What spec are you referencing for those #s?
300 circular mils per amp of current.
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If you've only got two conductors in open air
Are your cables suspended? Better safe than sorry.

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post #24 of 25 Old 04-18-2017, 12:11 PM
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300 circular mils per amp of current.
OK-- that seems a reasonable # to estimate for medium runs.

I gather that NEC is using 700 mils per amp for their current capacity recommendations, but there are a bunch of criteria lurking behind ampacity charts.

Quote:
Are your cables suspended? Better safe than sorry.
Mine aren't, but peak current from a 200W/channel amp into 4 ohm speakers would be ~7 A at a bit under 30 V.

I'm using AWG #14 wire; I've never noticed signs of the speaker cables getting warm.
Of course, I don't listen at anywhere near max volume, either....

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post #25 of 25 Old Today, 10:16 AM
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Late getting back to this.
Those are continuous current ratings of 3 hours or more with a large safety factor.
14AWG is rated for 15 Amps but in fact is good for 27 Amps continuous.
Music and movies are far from continuous.

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