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Title: THHN
Post by: Roger Talkov 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
Title: Re: THHN
Post by: Cailen Waddell 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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Title: Re: THHN
Post by: Roger Talkov 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? 
Title: Re: THHN
Post by: Rob Spence 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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Title: Re: THHN
Post by: Hal Bissinger/COMSYSTEC 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
Title: Re: THHN
Post by: Ron Hebbard 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!
Ron Hebbard.
Title: Re: THHN
Post by: Ron Hebbard 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!
Ron Hebbard.
Title: Re: THHN
Post by: Ivan Beaver 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.
Title: Re: THHN
Post by: Roger Talkov 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. 
Title: Re: THHN
Post by: Ivan Beaver 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.
Title: Re: THHN
Post by: Roger Talkov on December 05, 2016, 03:07:54 pm
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.

Agreed.  Makes perfect sense to me.
Title: Re: THHN
Post by: Kevin Graf on December 06, 2016, 08:58:37 am
Twisting a speaker wire pair has two advantages:
a] Reduces the self-inductance of the pair. High self-inductance on a long run can reduce treble response.
b] In rare cases, it can inhibit the speaker pair from acting as a interference antenna.
Title: Re: THHN
Post by: Ivan Beaver on December 06, 2016, 12:39:09 pm
Twisting a speaker wire pair has two advantages:
a] Reduces the self-inductance of the pair. High self-inductance on a long run can reduce treble response.
b] In rare cases, it can inhibit the speaker pair from acting as a interference antenna.
But the longer length will add capacitance-which will also reduce the HF.

I am not sure how much each would add or reduce to affect the overall response.

Of course it will greatly depend on a lot of factors, the twist ratio, the impedance of the load, the length of the run, the size of the insulation of the wire, the ga of the wire and so forth.

There is no "easy simple" answer, unless you know all of the details involved.  And even then you have to do some calculations in order to get a usable answer.
Title: Re: THHN
Post by: Rob Spence on December 06, 2016, 12:54:33 pm
At least with a loose twist, everyone will know they are paired and even electricians should know a twisted red/black isn't power.


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Title: Re: THHN
Post by: Kevin Graf on December 06, 2016, 02:58:57 pm
But the longer length will add capacitance-which will also reduce the HF.
In a loudspeaker system, the added capacitance will be trivial with regards to high frequency response.
But the added capacitance might make some legacy and boutique amplifiers unhappy.
Heck, running speaker cables in metal conduits or near metal beams can make some modern amplifiers unhappy.
Title: Re: THHN
Post by: Hal Bissinger/COMSYSTEC on December 06, 2016, 08:28:21 pm
But the longer length will add capacitance-which will also reduce the HF.

I am not sure how much each would add or reduce to affect the overall response.

Of course it will greatly depend on a lot of factors, the twist ratio, the impedance of the load, the length of the run, the size of the insulation of the wire, the ga of the wire and so forth.

There is no "easy simple" answer, unless you know all of the details involved.  And even then you have to do some calculations in order to get a usable answer.

How much shunt capacitance would make a noticeable difference in the HF response of an 8 ohm speaker? Now, I don't know what the capacitance per foot of a twisted pair of #10 THHN is but consider that the capacitance for a twisted pair of 24 ga outside plant telephone cable is .076 mfd per mile.

The only time I found twisting to be beneficial in speaker wiring was when I had to run individual runs to several 70 volt speakers that were tapped at 1/8 watt. Each speaker was individually switched back at the source and without twisted pairs, when a speaker switch was open there was still discernible sound from the speaker. Individual twisting took care of that together with a switch that would short the pair when open and off.

But like I said, I like to twist because it's easier to pull and identify, not because it needs to be twisted.

-Hal
Title: Re: THHN
Post by: Ivan Beaver on December 06, 2016, 09:12:52 pm
How much shunt capacitance would make a noticeable difference in the HF response of an 8 ohm speaker? Now, I don't know what the capacitance per foot of a twisted pair of #10 THHN is but consider that the capacitance for a twisted pair of 24 ga outside plant telephone cable is .076 mfd per mile.


Notice that I said it would affect the HF.

I DID NOT say how much or at what freq----------------

As with many other things, it is real easy to get "hung up" on things that don't make a difference in the intended performance range of the device.
Title: Re: THHN
Post by: Hal Bissinger/COMSYSTEC on December 07, 2016, 01:01:24 am
Notice that I said it would affect the HF.

I DID NOT say how much or at what freq----------------


And neither did I. My question was rhetorical.

-Hal
Title: Re: THHN
Post by: Ivan Beaver on December 07, 2016, 07:35:27 am
And neither did I. My question was rhetorical.

-Hal
Agreed

As with many things, it is easy to make a statement, and it may be true, but DOES IT MATTER?

For example.  I can go to the local lake and pee in it.

Then I could claim that I made the lake level rise because I peed into it.

While that is true, it does not make any REALIZABLE difference in the actual outcome.

But there are lots of products that love to make useless claims-and they are not lying-but they are not making a useful statement.

The end result is "does it matter", "can you easily hear the difference" etc

This is not saying it is meaningless, but a lot of "statements" lead people on paths that don't make a difference, while they completely ignore the ones that DO make a difference.

All to often people like to get hung up on the little things.

As the saying goes, "Choking on a gnat while swallowing a camel".
Title: Re: THHN
Post by: Hayden J. Nebus on December 07, 2016, 12:12:51 pm
Here's crosstalk across a roughly 25' run of parallel, untwisted, tight bundled #10 THHN. In the neighborhood of -30dB, it is audble in the high end.

This cable run, 36 amp channels for a 3 channel mains system, exits the rack bundled, and runs together across a tray for about 20 ft before breaking into individual runs of EMT per hang (L,R,C) .

Blue trace is one box driven in the R hang, on ax, in the nearfield. In the purple trace the mic hasn't moved, but L side is now driven.

(https://s23.postimg.org/p21z6hckr/crosstalk.jpg)   
Title: Re: THHN
Post by: Ivan Beaver on December 07, 2016, 01:08:27 pm
Here's crosstalk across a roughly 25' run of parallel, untwisted, tight bundled #10 THHN. In the neighborhood of -30dB, it is audble in the high end.

This cable run, 36 amp channels for a 3 channel mains system, exits the rack bundled, and runs together across a tray for about 20 ft before breaking into individual runs of EMT per hang (L,R,C) .

Blue trace is one box driven in the R hang, on ax, in the nearfield. In the purple trace the mic hasn't moved, but L side is now driven.

(https://s23.postimg.org/p21z6hckr/crosstalk.jpg)
Maybe I am missing something, but I am not sure that proves crosstalk.

Title: Re: THHN
Post by: Hayden J. Nebus on December 07, 2016, 02:07:27 pm
Maybe I am missing something, but I am not sure that proves crosstalk.

The blue trace is a normal electroacoustic transfer function. In the purple trace, there was one change to measurement conditions: input signal was removed from the amplifier connected to the loudspeaker under test, and applied to another amp.

So an amplifier which is not circuited to the loudspeaker creates acoustic output at the loudspeaker.
Title: Re: THHN
Post by: Hal Bissinger/COMSYSTEC on December 08, 2016, 12:33:41 pm
The blue trace is a normal electroacoustic transfer function. In the purple trace, there was one change to measurement conditions: input signal was removed from the amplifier connected to the loudspeaker under test, and applied to another amp.

So an amplifier which is not circuited to the loudspeaker creates acoustic output at the loudspeaker.

To do an accurate test- did you replace the driven speaker (L) with a dummy load so as to eliminate any possibility of the mic picking up sound from the driven speaker?

-Hal
Title: Re: THHN
Post by: Hayden J. Nebus on December 08, 2016, 01:26:07 pm
To do an accurate test- did you replace the driven speaker (L) with a dummy load so as to eliminate any possibility of the mic picking up sound from the driven speaker?

-Hal

Yes IIRC the test was repeated with the driven speaker both in and out of circuit.  Geometry and windowing were also on our side.

On site RMS voltage measurements with a quality DMM on the speaker conductors themselves corroborate this @ ~ -30dB crosstalk, and was replicated at the shop with a similar length bundle of multiple THHN pairs, resistive  load banks and an HP analyzer. Twisting the pairs at the shop bought a crosstalk reduction upwards of 10dB .  I suspect you could repeat this experiment and see similar results.

Judging by the HPF-iness of the coherence mask, I suspect the mechanism in this case is capacitive in nature.
Title: Re: THHN
Post by: Hal Bissinger/COMSYSTEC on December 09, 2016, 10:22:23 am
Yes IIRC the test was repeated with the driven speaker both in and out of circuit.  Geometry and windowing were also on our side.

On site RMS voltage measurements with a quality DMM on the speaker conductors themselves corroborate this @ ~ -30dB crosstalk, and was replicated at the shop with a similar length bundle of multiple THHN pairs, resistive  load banks and an HP analyzer. Twisting the pairs at the shop bought a crosstalk reduction upwards of 10dB .  I suspect you could repeat this experiment and see similar results.

Judging by the HPF-iness of the coherence mask, I suspect the mechanism in this case is capacitive in nature.

Yes it would be. It would be interesting to measure the capacitance between two parallel runs then substitute the equivalent capacitor in series with a speaker to see if you get similar results.

-Hal
Title: Re: THHN
Post by: Hayden J. Nebus on December 09, 2016, 04:37:14 pm
Yes it would be. It would be interesting to measure the capacitance between two parallel runs then substitute the equivalent capacitor in series with a speaker to see if you get similar results.

-Hal

I'd be interested to see if something like XHHW, which is available for near the price of THHN but has a jacket with different dialectric properties, would have measurably better performance than the THHN.

Belden 8477 #12 UTP is around $1.50 a ft. #12 THHN comes in around $.60/ft for a pair, XHHW is maybe 0.10 more per ft depending on where/how you buy it.



Title: Re: THHN
Post by: Hal Bissinger/COMSYSTEC on December 10, 2016, 12:16:18 pm
I have no experience with XHHW, it's a new product in the 14, 12 and 10ga sizes and only comes in stranded. Stranding is not a problem here but electricians like solid because you can wrap it around a screw. So I don't think XHHW is going to be widely stocked when THHN is available. But if you can get your hands on like 50' as a sample give it a try.

I suspect with parallel runs of Belden 8477 the crosstalk problem would be further minimized because of the twisting and the additional spacing due to the outer jacket.

-Hal
Title: Re: THHN
Post by: Jean-Pierre Coetzee on January 14, 2017, 03:51:17 am
I have no experience with XHHW, it's a new product in the 14, 12 and 10ga sizes and only comes in stranded. Stranding is not a problem here but electricians like solid because you can wrap it around a screw. So I don't think XHHW is going to be widely stocked when THHN is available. But if you can get your hands on like 50' as a sample give it a try.

I suspect with parallel runs of Belden 8477 the crosstalk problem would be further minimized because of the twisting and the additional spacing due to the outer jacket.

-Hal

I don't think skin effect has too much bearing on speaker cable runs but I can't see that an electrical inspector would prefer solid to stranded on electrical runs considering the added harmonics present in electrical systems these days. Electrical code here in South Africa calls for stranded at the very least on the neutral but if I remember right on all cables, would need to confirm with electrician though.
Title: Re: THHN
Post by: Hal Bissinger/COMSYSTEC on January 14, 2017, 03:22:45 pm
I don't think skin effect has too much bearing on speaker cable runs but I can't see that an electrical inspector would prefer solid to stranded on electrical runs considering the added harmonics present in electrical systems these days. Electrical code here in South Africa calls for stranded at the very least on the neutral but if I remember right on all cables, would need to confirm with electrician though.

Here in the US if there are harmonics we upsize the neutral. That was common years ago with offices full of computers for instance. But it would be unusual these days to see such inefficient power supplies. All wire can be had in either solid or stranded with the exception of #6AWG and above. That can only be had in stranded. Only reason being who would want to bend solid?

-Hal
Title: Re: THHN
Post by: Adam Kane on January 17, 2017, 10:20:32 am
Here in the US if there are harmonics we upsize the neutral. That was common years ago with offices full of computers for instance. But it would be unusual these days to see such inefficient power supplies. All wire can be had in either solid or stranded with the exception of #6AWG and above. That can only be had in stranded. Only reason being who would want to bend solid?

-Hal

You can still get solid bare ground wire in 6awg and 4awg. Horrible to work with.

Friend of mine was selling a house and the home inspector called out grounding issues with rods/piping etc. I told him what to buy and I came to fix everything. I show up and there's a coil of #4 solid by the panel. Had to use linesman pliers and every bit of muscle I had to bend it into lugs in the panel and into ground clamps. He paid me in pizza though...so I guess it was kinda worth it...?
Title: Re: THHN
Post by: Hal Bissinger/COMSYSTEC on January 18, 2017, 07:55:07 pm
You can still get solid bare ground wire in 6awg and 4awg. Horrible to work with.

I know you can get #6 solid (I have some) that's sold to the telecom industry for grounding. Gray PVC jacket. It's not UL listed per NEC so it can only be used for communications grounding. I've never heard of #4 solid (where the hell did he find that, probably Ebay right?) but it is the same case- not listed so it can't be used in an electrical installation though utilities can use anything they want since they don't come under the NEC.

-Hal
Title: Re: THHN
Post by: Stephen Swaffer on January 23, 2017, 12:56:52 pm
http://www.cesco.com/b2c/product/Copper-Building-Wire-Bare-Cable/603925

I've used it before for grounding and the AHJ passed it.  I'm not sure what testing UL is going to do on a 100% copper solid bare conductor? 

For that matter, since a ground can be "bare, covered, or insulated", other than smoke producing properties (a concern no matter the use), the only reason I see for the gray not being acceptable is the color-which needs to be green or green with a yellow stripe.

Thought you might find the description interesting-bare cooper for overhead transmission wiring. I've ran into some recently-I honestly didn't know the #4 bare was marketed for such use!
Title: Re: THHN
Post by: Hal Bissinger/COMSYSTEC on January 24, 2017, 12:33:48 am
http://www.cesco.com/b2c/product/Copper-Building-Wire-Bare-Cable/603925 (http://www.cesco.com/b2c/product/Copper-Building-Wire-Bare-Cable/603925)

I've used it before for grounding and the AHJ passed it.  I'm not sure what testing UL is going to do on a 100% copper solid bare conductor? 

For that matter, since a ground can be "bare, covered, or insulated", other than smoke producing properties (a concern no matter the use), the only reason I see for the gray not being acceptable is the color-which needs to be green or green with a yellow stripe.

Thought you might find the description interesting-bare cooper for overhead transmission wiring. I've ran into some recently-I honestly didn't know the #4 bare was marketed for such use!

I stand corrected. Obviously #4 bare is available and as such can be used for grounding and bonding.

-Hal