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Topic: Question about speaker lines

Richard Hamilton
Phenomenal Film Handler

Posts: 1341
From: Evansville, Indiana
Registered: Jan 2000

posted 10-03-2010 10:58 AM

quote: Randy Stankey
When you are making up XLR audio/mic cables

Randy, I was going through some old files and this is a good read on making cables. RANE It has very good drawings on the last 2 pages. Luckily it's still online, I printed it quite a few years ago.
Rick

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 10-03-2010 01:58 PM

Okay...so I've been contacted about a response to my post...I have not been on line too much this past couple of weeks due to a heavy work load...

quote: Sam D. Chavez
Oh Piffle, this is just anal retentention to an extreme

Not really...it is just getting the concept of not adding additional rotations to a conductor. You are trying to twist the pairs relative to each other, not unto itself.

quote: Sam D. Chavez
We don't really know how Belden twists them do we

I can not say that I've been in the Belden cable plant...this is true...but I can guarantee you, they don't do it via a drill. In fact, no cable machine in commercial use (that I've searched for) uses a drill or drill like apparatus.

Quite frankly, the notion is plain stupid, in a mechanical sense. One would have to to know the metallurgy of the cable to know just what forces may be exerted upon it. Cable manufacturers will provide bend radius and possibly tinsel strength. They don't provide "over-twist amount" as one is NOT supposed to add additional twists to cable. That is the cable manufacturer's job.

quote: Tony Bandiera Jr
Steve, FYI the FACTORY makes its twisted pairs using a method just like using a drill but on a bigger scale, which BTW would be MORE likely to damage the wire.

Tony, you don't have a clue as to what you are talking about, on this one. They don't use drills and they don't add twists to the individual conductor as they make twisted pair cable. It is only your perception that they do. A cable manufacturer can add a twist if they know what the effects are as they can tightly control the twist-per-inch of the final product. They also have the information on the metallurgy of the conductors that you and I do not have to know if/when the limits are reached. Heck, the making of the conductors often is from the stretching, pressing...etc of larger material.

quote: Tony Bandiera Jr
Unless you're a gorilla and keep twisting beyond tight there is ABSOLUTELY NO WAY you're gonna even come close to damaging the inner stranding of THHN 14 or 12ga wire.

Again, you speak knowledge that you do not have.

quote: Tony Bandiera Jr
And like I said before, any damage you would cause would be visible.

Wrong again...and there is a visible damage to the drillers out there...the springy ends they end up with that most cut off...the rest is sprung but usually less so.

quote: Tony Bandiera Jr
I have done literally hundreds of installs over the years with that method and NEVER had a line fail.

You've done it WRONG hundreds of times and I suspect you will continue to do so...no matter how many times you do it wrong, it doesn't make it right.

quote: Sam D. Chavez
The real issue is whether the twist does any real good.

It is good for noise (not necessarily hum) immunity. The noise is often inductance from its neighbor wire running in close proximity on a long run in a parallel fashion (in conduit). I've witnessed where two theatres shared a common conduit (electrical ran one large conduit and T-ed off at the screen end)...one theatre's sound played out of the other theatre's speakers (at a reduced level, of course). While it is a completely different discussion about the stupidity of using th single conduit, it does show that one will get crosstalk between channels within the same theatre if non-twisted cable is used. You are MUCH less likely to pick that off since if the center speaker is playing loudly, you are much less likely to hear some minor crosstalk in the Left, Right or Sub channels. Twisted cable will likely stop that.

Twisted cable gets its noise immunity by increasing the likelihood of any "noise" impressing itself on BOTH conductors about identically...thus the potential difference between the two conductors, with respect to the noise, is approximately zero. In long parallel runs, it also increases the spacing between conductors, further reducing the chance of inductance between adjacent cables.

quote: Randy Stankey
When you are making up XLR audio/mic cables, if you run the cable the right direction, when you are cutting and soldering, the black, white and shield conductors will line up with Pin-2, Pin-3 and Pin-1 respectively and you won't have to untwist them in order to make the joint.

Randy is correct again. Furthermore...when making up electrical plugs...getting the lay right will also have the conductors line up with their respective terminals...easier than making one conductor pull tightly over and stressing the whole connection.

quote: Louis Bornwasser
I use thhn stranded, do not twist any wire, and not only never have hum "issues," but usually get the appropriate curve within 2 db without touching a single third octave control.

See above...if you use grounded conduit...you are less likely to get hum issues...but you do have measurable crosstalk. Frequency response has little to do with stranding or twist at audio frequencies. If your cable is too small such that resistance becomes a factor...aside from heating up the cable, you will get bass anomalies from under-damping.

-Steve

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Tony Bandiera Jr
Film God

Posts: 3067
From: Moreland Idaho
Registered: Apr 2004

posted 10-03-2010 03:04 PM

quote: Steve Guttag
Tony, you don't have a clue as to what you are talking about, on this one. They don't use drills and they don't add twists to the individual conductor as they make twisted pair cable. It is only your perception that they do. A cable manufacturer can add a twist if they know what the effects are as they can tightly control the twist-per-inch of the final product. They also have the information on the metallurgy of the conductors that you and I do not have to know if/when the limits are reached. Heck, the making of the conductors often is from the stretching, pressing...etc of larger material.

Steve, I resent your attitude in your responses...you HAVE NO CLUE what my experiences are, just as I have NO CLUE what YOUR experiences are.

I have seen first-hand how twisted pair wire is made and the machine that does it (more like a lathe than a drill I will concede) puts no more or less twist force than one could do by hand carefully. It has the advantage of course of maintaining a constant rate of twist and tension.

And by clamping BOTH conductors into a drill you are NOT adding individual twists to each conductor within the twist.

Finally we are not talking about adding a twist to a twisted pair.

quote: Tony Bandiera Jr
Unless you're a gorilla and keep twisting beyond tight there is ABSOLUTELY NO WAY you're gonna even come close to damaging the inner stranding of THHN 14 or 12ga wire.

quote: Steve Guttag
Again, you speak knowledge that you do not have.

Attitude again...how do you know that? I have been doing this for 29 years and have been working for electrical contractors as well during that same time frame. We have done our own tests to PROVE that unless you make a VISIBLE overtwist you are NOT harming the inner conductor in any way.

quote: Tony Bandiera Jr
And like I said before, any damage you would cause would be visible.

quote: Steve Guttag
Wrong again...and there is a visible damage to the drillers out there...the springy ends they end up with that most cut off...the rest is sprung but usually less so.

The rest is NOT sprung to any degree that would cause damage. Again, I and various EC's I have worked with have done tests to prove it. Of course the ends do get overtightened which is why they get cut off.

quote: Tony Bandiera Jr
I have done literally hundreds of installs over the years with that method and NEVER had a line fail.

quote: Steve Guttag
You've done it WRONG hundreds of times and I suspect you will continue to do so...no matter how many times you do it wrong, it doesn't make it right.

Then I was also taught the wrong way by a very well-known tech who I am sure you wouldn't dare challenge publically like you're doing here.

Just because someone doesn't do it YOUR way doesn't make it wrong (or worse or better than) your way.

On a lighter note, Richard, thank you for that link. Very handy information in that document. [beer]

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 10-03-2010 03:12 PM

Tony...sorry you are offended...you and ANY tech...no matter how publically known, I would challenge...it is just plain wrong...you can get around the physics of it.

Again...put a line on any conductor such that it is on the same side for its length...when you are done with the twisting...that line better not spiral. If it does, you have stressed the cable, period. With a drill, you are going to spiral the cable.

With a proper machine, you are not.

Believe what you want...there are a lot of guys that coil up cable by coiling up over their shoulder and hand...and don't see the harm either.

Sorry again, that you are upset...but it makes you no less wrong.

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 10-03-2010 04:03 PM

There exists NO tech that is right about everything. Also age and number of years doing the job has nothing to do with whether that person is doing a job the best way or not. Sometimes that boils down to opinion, other times it is flat out wrong. I know of some techs who have been doing this sort of work since forever, and yet I will see them do completely bonehead things. All I can do is turn my head the other way and pretend I didn't see what they just did because there comes a point when someone has been doing a job for a long time...particularly their entire life...that you cannot tell them they are wrong, no matter how badly they are fucking up.

Steve is technically correct here. I say technically because I've never seen it affect (at least to what I have seen) the performance of the wire, but then again I've also never bothered to do any critical testing. That being said, my installations use pre-twisted wire.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 10-03-2010 05:01 PM

quote: Tony Bandiera Jr
And by clamping BOTH conductors into a drill you are NOT adding individual twists to each conductor within the twist.

I think that is where you are missing the point and the physics of the problem. You are clamping, effectively, both ends. It is the clamping in the drill where you get into the problem.

To prove the point...take the other conductor out of the drill and leave just the one...all else the same...turn the drill on with just the one conductor...and then examine what you are doing...you are merely twisting the one conductor tighter than the factory. The addition of the second conductor didn't change that...it only added an additional dynamic of the conductor interaction.

If you MUST use a drill...you can fake what a professional twisting machine does by making a mandrel and plate. Use the bar stock included with most any Potts/Strong platter. Cut it so it is about 6-inches long. Drill three holes. One in the middle and one near either end but evenly spaced off of the middle. On the middle hole, either tap it for a proper mandrel or use a screw and nut. On the outer holes polish them smooth and chamfer them so the wire will not chafe going through. Chuck this up in your drill. Feed each wire through its respective hole. and tie a knot in each so that the wire can not come back through the hole.

Now, since each wire is allow to rotate freely as it is coiled and is not held in the chuck, it will greatly reduce the amount of extra twisting that is done along its length. Again, a proper twisting machine will add no extra twists to the individual wires but this will will approximate it (depends on the stiffness of the individual wires. The stress will be less as you get near the end (with the drill) as the "fixed" point (Where the twisting is occurring) gets closer to the apparatus, the wire will more easily be able to untwist.

Steve

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Eric Robinson
Jedi Master Film Handler

Posts: 538
From: Santa Rosa, CA
Registered: Jan 2005

posted 10-03-2010 05:09 PM

quote: Brad Miller
There exists NO tech that is right about everything.

Yes...true...just when I think I've mastered something, I learn something new about it that had not anticipated. It's more beneficial to be open and listen and ask about things.

That of course is just my opnion, and I am right about everything, so you should believe it [Big Grin]

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003

posted 10-03-2010 05:12 PM

Steve is always technically correct and he has a lot of science behind him, but the relative importance of some of what he is correct about varies a lot, as in "much ado about nothing". Tony and others like me have common sense on our side and have been known to do pretty good work over a long period of time.

As a practical matter, it is very difficult to damage wire typically used for speakers to any degree worth mentioning. It is made to be pulled thru a pipe with a winch after all, and should save our ammo to discuss something of some importance.

There is the issue of assuming the wire making companies use good science in the making of copper cable. They do a pretty good job of torturing the wire in the making of it and the welded joints are not always perfect I'm sure. About on a par with lab splices I would guess. We are talking about wire that sells for $50.00/1000 Ft. retail. How good can it really be?

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 10-03-2010 05:23 PM

Sam,

It is the common sense that is failing here, in my opinion. It is clear that the wire is being stressed or it wouldn't "spring" at any end.

Wire is indeed designed to be pulled and has a rated tensile strength for that...which is diminished if improperly twisted as you will have used some of that by torturing it in your drill.

I'm just amazed that some will see a cable get all sprung and also watch how the cable twists using the typical drill method and not think anything is wrong there. Common sense should dictate otherwise.

As I said, I don't think I'm going to sway a person that thinks there is no problem...but there is right and wrong...give a choice, do it right.

As a side note...I'm not always technically correct...but I will admit when I'm wrong...sometimes my own "common sense" will get the best of me. I do, generally, try to think things out.

Steve

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 10-03-2010 10:19 PM

This conversation really reminds me that being a theater technician really has very little to do with having specific knowledge on how a piece of equipment works or, in this case, things like how to hook up wires. It's really more about how to look at a certain situation and make a decision how is the best way to get the results you are looking for.

Your employer isn't paying you to know that the flux capacitor needs 1.21 gigawatts of electricity to function. He's paying you for your experience and your ability to size up a situation and come up with an answer to solve his problem.

Example... For years I soldered microphone cables together whichever way the cable happened to end up. Then, one day, I was making up a bunch of XLR cables and discovered that the cables were a lot easier to solder together if I ran the wire one way versus the other. Now, I always make them up the same way. I don't know which way is the right way from memory. I just know that I need to check the lay of the conductors and put the ends on in the right order.

This is not something that a lot of people know. Those who do know it probably don't know exactly when and where they learned that unless they were taught as part of a technical course. To be honest, there aren't a lot of technical courses in theater technology. Yes, there are some but not a lot.

So, the bottom line is that it is the technician's job to decide whether things like cable twist are important to the task at hand and how much time and trouble are necessary to deal with the problem. At minimum, I would certainly consider it as a factor.

On the other hand, there are so many things I have done in the past that have come back to bite me in the ass later on, even if it's only a minor inconvenience.

An example that I use often is wrapping microphone cables for storage. Most people think I'm being picky about wrapping cables in "over/under" fashion but I don't know how many times I have had to set up a microphone at the last minute before a show and had to struggle with a tangled cable or troubleshoot twisted, broken conductors. As far as I am concerned, that extra 30 seconds it takes to wrap a cable properly for storage will be more than made up for in time saved troubleshooting later on.

Even though I don't think twisting wires in a drill will cause the end of the world, I'll certainly file that in my "mental Rolodex" and consider it the next time I have to wire up some speakers.

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003

posted 10-04-2010 09:19 AM

The reason ordinary #14 or 12 wire was used back in the day is cost and ease of pulling thru a pipe. Wrapped and/or twisted Belden takes more space in a pipe and costs more. So we go back to twisting to keep track of channel pairs. This is important as I have come across the +/- pair being misidentified and causing some strange problems trouble shooting systems.

It all falls into the category of practical.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 10-04-2010 12:20 PM

I've definitely seen the wrong identified pairs. Particularly on the "black" as most amplifiers use a common "-" terminal and it is often referenced to ground in solid-state amps. It having the wrong black wire will often work but, as Sam states, odd results can ensue...especially if an amplifier is pulled for repairs...you may "think" you still have Center connected!

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Robert Minichino
Master Film Handler

Posts: 350
From: Haskell, NJ, USA
Registered: Dec 2005

posted 10-04-2010 01:17 PM

You can buy pre-twisted THHN without an overall jacket. The jacketed stuff is nicer to work with (finer strands, plus it's easier to identify), but it's way more expensive and eats into conduit fill. Regardless, my time is worth too much to bother twisting it myself, although I doubt the drill method is going to hurt the wire too much.

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Louis Bornwasser
Film God

Posts: 4441
From: prospect ky usa
Registered: Mar 2005

posted 10-04-2010 01:52 PM

The ONLY wire I've ever twisted is small diameter solid hookup wire to avoid cable ties. The drill is common with this. I see no point to twisting stranded cable.

I have seen Belden video showing cable twisting. The system is similar to the system that weaves a woven shield on better cables like #8412, the reference standard heavy duty microphone cable (no Beld-foil). Louis

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003

posted 10-04-2010 01:56 PM

I never pull jacketed speaker cable through a pipe as it's a waste of money and a real hassle to pull without wire lubricant AKA, "love butter".

Also, the jacket tends to stick to the conduit and it's a real pain if you ever need to add more wire or pull it back out of the pipe. I've actually had jacketed audio wire stick so bad it broke off somewhere inside the pipe leaving me up the creek.

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