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Author Topic: THHN  (Read 4093 times)

Roger Talkov

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THHN
« on: December 01, 2016, 11:19:17 am »

All:
I'd like to get a feel for how many people use 10 gauge THHN for speaker wire when you have conduits in place. Use of this has come up with some clients due to its much less cost.  We have used it in the past out of necessity for some stadium type installs but it seems like it hasn't come up on this list much and I'd like to know others thoughts.

Regards to the list,
Roger
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Cailen Waddell

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Re: THHN
« Reply #1 on: December 01, 2016, 11:25:06 am »

Stranded THHN should be fine for speaker wire in my opinion.  The only concern I would have is the AHJ not understanding it is for a low voltage load and question a jbox with a panel that had line and speaker connections but no high/low divider.


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Roger Talkov

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Re: THHN
« Reply #2 on: December 01, 2016, 02:20:11 pm »

Ideally do the pairs need to be twisted together or can lets say 8 wires be pulled through one conduit without a problem? 
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Rob Spence

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Re: THHN
« Reply #3 on: December 01, 2016, 06:29:33 pm »

All:
I'd like to get a feel for how many people use 10 gauge THHN for speaker wire when you have conduits in place. Use of this has come up with some clients due to its much less cost.  We have used it in the past out of necessity for some stadium type installs but it seems like it hasn't come up on this list much and I'd like to know others thoughts.

Regards to the list,
Roger

Much less cost than what?


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rob at lynxaudioservices dot com

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Hal Bissinger/COMSYSTEC

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Re: THHN
« Reply #4 on: December 01, 2016, 07:47:41 pm »

Stranded THHN should be fine for speaker wire in my opinion.  The only concern I would have is the AHJ not understanding it is for a low voltage load and question a jbox with a panel that had line and speaker connections but no high/low divider.


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Are you saying that an inspector could mistake THHN used for speaker wiring for line voltage wiring? No. Any inspector should be competent enough to know that THHN is used for more than line voltage. Of course there would be no question as long as the speaker wiring is properly installed as low voltage and not mixed with line voltage conductors as required by the NEC.

One time I had several thousand feet of TFFN  twisted up for a 70 volt Class 1 system run in conduit. Red and black 18 ga (16 and 18 ga can only be had in TFFN fixture wire).  When you see the twisted red&black you automatically know that it's not line voltage.

It's quite common in movie theater installations to use THHN for the speaker wiring. I like to have the pairs twisted if just for ease of identification and installation. THHN and TFFN has to be a lot cheaper than the Belden alternatives and is the only way to install anything requiring Class 1 wiring.  I believe it was Power and Tel Supply (the old Clifford of Vermont) that was happy to twist up whatever I needed and provide it on reels.

Also, I would suggest that you get to know NEC article 725 at least as it pertains to Class1, CL3 and CL2 wiring which will cover all speaker wiring.

-Hal
« Last Edit: December 01, 2016, 07:50:49 pm by Hal Bissinger/COMSYSTEC »
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Ron Hebbard

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Re: THHN
« Reply #5 on: December 04, 2016, 09:40:37 am »

All:
I'd like to get a feel for how many people use 10 gauge THHN for speaker wire when you have conduits in place. Use of this has come up with some clients due to its much less cost.  We have used it in the past out of necessity for some stadium type installs but it seems like it hasn't come up on this list much and I'd like to know others thoughts.

Regards to the list,
Roger
Used it a lot.  Have it twisted up in Red and Black for low impedance speaker runs and have even done parallel pairs as parallel feeds for higher power and / or more distant loads.  Whether IBEW electricians are from an electrical or electronic mindset they can always agree when they get to an amp output, or a speaker input, black goes with black and red goes with red.  No more debates about whether the white conductor goes on the red terminal or the black one.
Toodleoo!
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Ron Hebbard

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Re: THHN
« Reply #6 on: December 04, 2016, 09:46:41 am »

Ideally do the pairs need to be twisted together or can lets say 8 wires be pulled through one conduit without a problem?
From a cross-talk perspective, you're better off with the pairs twisted but realize they'll occupy more pipe space when they're twisted.  I've done both using twisted pairs wherever I've had room and dropping back to untwisted THHN wherever I was too tight for space.
Toodleoo!
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Ivan Beaver

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Re: THHN
« Reply #7 on: December 04, 2016, 10:59:20 am »

From a cross-talk perspective, you're better off with the pairs twisted but realize they'll occupy more pipe space when they're twisted.  I've done both using twisted pairs wherever I've had room and dropping back to untwisted THHN wherever I was too tight for space.
Toodleoo!
Ron Hebbard.
Twisting only really helps in signal cable in which there is an amplifier at the end of the cable.  There is no real advantage to twisting speaker cable in terms of signal quality.

This is the common mode rejection ratio and is important when the next stage is an amplifier.

In the case of speakers, the next stage is a loudspeaker, which is actually a "non amplifier" and loses energy in the conversion process.
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Ivan Beaver
Danley Sound Labs

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Roger Talkov

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Re: THHN
« Reply #8 on: December 05, 2016, 12:40:17 pm »

Thank you all.  So, in summary, if THHN is used, Twist it if you want and can afford the space in the pipe. Don't bother twisting if you need the space in the pipe- but either way, quality (crosstalk or common mode etc) of the signal should not be an issue when used in reasonable lengths v gauge. 
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Ivan Beaver

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Re: THHN
« Reply #9 on: December 05, 2016, 01:09:08 pm »

Thank you all.  So, in summary, if THHN is used, Twist it if you want and can afford the space in the pipe. Don't bother twisting if you need the space in the pipe- but either way, quality (crosstalk or common mode etc) of the signal should not be an issue when used in reasonable lengths v gauge.
Think of it this way.

If cross talk in speaker wires in conduit was an issue, would it not be MORE of an issue in multi core speaker cable?  Where the conductors are forced to be very close to each other?

I have never heard of anybody complaining about crosstalk in a NL8 or socopex speaker cable.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!
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