Film-Tech Forum ARCHIVE: Speaker wire gauge

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Posted by Tom Wienholt (Member # 1510) on 01-15-2003, 12:21 AM:

I just got done reading old topiics about proper speaker wire gauge. Is there a chart somewhere that gives this information. Basically, i need to know what gauge speaker wire to use for an auditrum that is 50 feet long. Each wire will be at most 100 feet in length. Any help would be appreciated.

Posted by Jean-Michel Grin (Member # 1360) on 01-15-2003, 02:16 AM:

Hi,

In ours Theaters we use at least for short distance, 16 AWG ty cable (almost 1.5 square milimeter for HF) and 14 AWG (almost 2.5 square milimeter for LF and Sub)
For very big auditiorums, i mean that 14 AWG must be sufficient or better for LF use 12 AWG.

Good Luck !

Jean-Michel

Posted by Tim Reed (Member # 137) on 01-15-2003, 03:05 AM:

I always used #12 for stage channels, #10 for subwoofers, and #14 for surrounds. In a small house, you can probably get by with a size smaller on each. All conductors 600v, THHN stranded, and make sure the electrician either numbers or runs different colors for each. I also have them pull an extra conductor or two while they're at it, you never know what lies ahead.

Posted by Jon Bartow (Member # 241) on 01-15-2003, 07:34 AM:

I'm with Tim: #12 for stage (unless it's a big triamp system then the LF will have #10) #10 for sub and #14 for surrounds (a home run to the booth for every speaker) I allways have the electricians pull extra wires for the stage and for the back wall if no rear surrounds are originally installed.
For the stage I usually have them pull 6 pair #12 for the three stage channels (bi-amped) and two pair #10 for the subs and a spare pair of each , just in case. And I have them leave a string or two in the conduit for the future.
Jonathan

Posted by Scott Norwood (Member # 30) on 01-15-2003, 08:03 AM:

For what it's worth, John F. Allen had an article on this topic in a recent issue of Boxoffice magazine.

Posted by Don E. Nelson (Member # 1049) on 01-15-2003, 03:20 PM:

Tom,
In order to ensure the best possible sound out of your theatre sound system, I would recommend you research this speaker wire subject throughly before buying just any old gauge of speaker wire from the local hdwe. store. Years ago, (1974) my roommate at the time realized that interfacing the amplifier to the speaker system on any type of sound system was the most overlooked component. He researched the cable industry and did some electronic/physics research and started buying samples of specially produced wire from Japan. From this humble begining ,he started a company called The Monster Cable Co in San Francisco. He is now the "head monster", and his name is Noel Lee.
It is critical that the signal from the amplifier to the speaker system is not limited in any way by the connection wire. That is why a lot of concert sound companies do away with speaker wire completely by physically locating the amps aon back of the sound cabinets. (directly coupled)
To make a long story, not quite so long,
Noel found that there are three basic electrical properties which combine to form the total impedance of a wire: resistance, capacitance, and inductance . The capacitance effects the high frequencies that travel on the outside of the wire. Resistance (resistive impedance, measured in Ohms) is usually not a problem, even with inexpensive electrical cables. The real culprits in cable transmission are capacitance, measured in picofarads ) per foot, and inductance, measured in microhenrys (µH).
The damping control of the amp is critical to controling the speaker cone movement accurately. The types of wire connectors you use at both ends are also critical.

Now this may sound like info that only an audiophile, with a high end system, has to worry about t but if you don't think of you theatre sound sytem as a really good stereo system, your in big trouble and it will just sound like a PA. system . I believe something as simple as speaker wire is the reason some theaters sound "great " with good stereo imaging, presence and dynamic range while others are just (ho hum)average. Best of luck.

Posted by Kenneth Wuepper (Member # 1174) on 01-15-2003, 06:38 PM:

Avoid at all cost the temptation to use multi-conductor cable for the amp to speaker connection. Additional coupling of the signals from one amplifier output into the others in a multi cable will cause some very queer problems.

In one occasion, the amplifiers were running very warm and the signal was sort of fuzzy. The volume was not sufficient to have caused amplifier overload yet the sound was second rate. A scope check of the outputs from the amplifiers showed that there was an oscillation at pitches above human hearing range and these signals were overloading the power amplifiers. Sound amplifiers with negative feedback compensation for achieving good frequency response are most likely to have this problem. Amplifiers without transformers in the output circuits also are susceptible to ultrasonic oscillations. Capacitive coupling in bundled cabled wires is greater than in open wires or even wires in counduit.

The idea of locating the power amplifiers back stage and feeding them input signal with balanced and shielded cables is a sound one. (Pun Intended)

KEN

Posted by Mark Gulbrandsen (Member # 72) on 01-15-2003, 07:54 PM:

Also when your electrician does the wire install be sure that he twists EACH PAIR by either using a drill, or by getting the wire pre-twisted. The Drill is LOTS CHEAPER to do though. Expect pre-twisted wire to be AT LEAST double in price!! Yes, you have to up-size the conduit as well! Twisting the pairs will eliminate mutual coupling between channels, and cancle out any RF that may want to feed back down the speaker runs to the booth. The picture is of a large install job we did last September. Each run was about 200' long and we used #10 wire. The system was Quad-amped so the electricians installed a 4" couduit run for us and pulled in two extra strings as well.

Notice that one roll has the wire comming off the top and the other off the bottom. This helps the wire twist together better and also makes the wire relax a bit better. Ya have to let off slowly to relax it...run the drill backwards a bit or else it'll turn into a tangled mess, or might whip back at you...no joke [Eek!]

. Use an eyebolt in the drill and have a seciond person keep some back tension on the rolls of wire, or you'll tangle!. Use stranded wire, THHN insulated(double insulated). Stranded is lots easier to work with and sounds much, much better than solid because of skin effect.

Definately the longest rune I've ever twisted in the field...ok parking lot. Only took about 5 hours to do all the twisting...we had great weather for it.....
Mark @ CLACO

Posted by Michael Schaffer (Member # 1204) on 01-17-2003, 10:42 AM:

quote:
Noel found that there are three basic electrical properties which combine to form the total impedance of a wire: resistance, capacitance, and inductance

Wow! I would have thought that that was already known by the 70s. Your friend is a pioneer of electrotechnics! Is there a unit named after him?

Posted by Jack Ondracek (Member # 1466) on 01-17-2003, 12:37 PM:

Nothing negative intended toward Noel... but I found one product of Monster Cable to be a bit over the top... probably rampant marketing at its "best"...

Monster sells a short piece of telephone cable with modular connectors on each end... intended to patch between a modem and the wall jack. The product description highlighted how super wire and gold connectors could "help" raise data rates and reduce errors.

I guess you weren't supposed to wonder about all the wire going between the other side of the wall and the central office... [Roll Eyes]

Posted by Gordon McLeod (Member # 33) on 01-17-2003, 12:58 PM:

Specialty speaker cables are vastly overated

Posted by John Pytlak (Member # 331) on 01-17-2003, 02:45 PM:

Some articles about speaker wire and damping factor:

http://www.tnt-audio.com/clinica/cat5questions_e.html

http://www.canare.com/cat10pdf/p31.pdf

http://www.procosound.com/downloads/guides/htc_speaker.pdf

http://www.procosound.com/downloads/speaker_guide.pdf

http://www.sweetwater.com/insync/word/dampingfactor

Posted by Steve Guttag (Member # 268) on 01-17-2003, 07:30 PM:

As always, I never recommend to use a drill to twist wires into cables...it increases the stress on the individual conductors, and ultimately the individual strands. A proper lay will not add any rotation to the individual conductors and will have zero spring to the cable (without having to go backwards).

Steve

Posted by Mark Gulbrandsen (Member # 72) on 01-17-2003, 08:07 PM:

Steve,
I don't dispute that you will be ading at least some stress tothe twisted pair....Twisting wire yourself however is sometimes the only way to make deadlines and keep within budget most of the time. I've also used alot of pre-twisted pair as well. Try getting that much thhn #10 twisted pair sometime...good luck! Has to be custom done even here in SLC where there are almost 60 electrical supply houses. None of them have proper equipment to twist wire. Also pre-twisted wire will normally at least double in price and sometimes be triple. Myself, and and I also know Gord have always twisted wire with only excellent results from doing so. Have yet to have any sort of problems in 20 years from the slight stress that twisting might add to the conductors. Copper is one of the most resilient of the metals and is quite good at taking the small stress added. Perhaps though you have had problems from doing it this way...but I have yet to.
Mark @ CLACO
www.clacoequipment.com

Posted by Mark Gulbrandsen (Member # 72) on 01-17-2003, 08:19 PM:

Gord said,
"Specialty speaker cables are vastly overated"
___________________________________________________________________

Sorry Gord,
You're a bit off with that statement. First, you have to have quipment with high enough resolution before you can hear the differences. Few, if any theatres, or dubbing stages fall into the high resolution catagory. There are alot of things that affect how a cable sounds, some of these differences can even be measured, and some cannot. Capacitance plays a big factor, how much resistance, and how much reactance the cables introduce will also cause differences in overall sound. Moleculuar structuire of the copper, or what ever metal is another big factor. Different amplifiers and different speakers all behave differently with differing amount of capacitance, reactance and resistance....ya can't deny that!

Just don't expect to be able to hear huge differences, usually they are slight. Another thing that does have effect on sound is the braid of the conductors, and how the cable is braded together. There is alot more to it but these are just some of the reasons. If ya want to know more research it........
Mark @ CLACO
www.clacoequipment.com

Posted by Tim Reed (Member # 137) on 01-17-2003, 08:22 PM:

quote:
I believe something as simple as speaker wire is the reason some theaters sound "great " with good stereo imaging, presence and dynamic range while others are just (ho hum)average.

Hi Don, I believe the differences you notice have more to do with auditorium acoustics than with speaker wires. I like the Monster Cable concept -- and all your points are valid -- but I think the reactive components of stranded THHN wire simply do not amount to that much at audio frequencies. It's enough to render solid wire useless, as Mark noted, but regular ol' stranded wire is more than adequate, in my experience. Sure, there are differences, but it would indeed take a golden ear to hear it (if at all).

I'd be willing to bet much of the claimed subjective differences come from simply knowing there is special cable in use.

Posted by Mark Gulbrandsen (Member # 72) on 01-17-2003, 08:28 PM:

Tim, If you understand the basics of Skin effect I believe you'd agree that its the primary reason that theatres with solid core wire usually sound worse, given the same speakers,room, etc, than theatres wired with stranded wire.....That has always been my experience anyway.....
Found this a couple of days ago and is quite easy for anyone to understand......
______________________________________________________________________
skin effect: The tendency of alternating current to flow near the surface of a conductor, thereby restricting the current to a small part of the total cross-sectional area and increasing the resistance to the flow of current. Note: The skin effect is caused by the self-inductance of the conductor, which causes an increase in the inductive reactance at high frequencies, thus forcing the carriers, i.e., electrons, toward the surface of the conductor. At high frequencies, the circumference is the preferred criterion for predicting resistance than is the cross-sectional area. The depth of penetration of current can be very small compared to the diameter.
Mark @ CLACO
www.clacoequipment.com

Posted by Mark Gulbrandsen (Member # 72) on 01-17-2003, 09:28 PM:

Owwwweeee Steve,
I forgot to ask in the last post I made as you said....
"As always, I never recommend to use a drill to twist wires into cables..."

So other than buying it already twisted what DO you reccomend to twist a wire pair? I'm sure alot of others here would also be interested to know your way of doing it....and does your way eliminate all the stress?
Thanks,
Mark @ CLACO
www.clacoequipment.com

Posted by Gordon McLeod (Member # 33) on 01-17-2003, 10:02 PM:

mark In a large room even with accepatble NC25 and RT60 the speaker cable is more of an issue of losses due to reistance than anything else
Skin effect is only an issue well above the audio spectrum.
If it was such an issue then PCB's would not be able to work as they are by nature solid conductors dealing with much higher gains

Posted by Mark Gulbrandsen (Member # 72) on 01-18-2003, 12:45 AM:

Gord,
I agree that resistance is the main issue in a theatre, or any really long run for that matter...no dispute there. I was inferring a high resolution type situation where one can hear every slight change between cabling. There are sometimes very stark differences between cables. Thats why I said that in a theatre application you may hear only very subtle difference. In my experience though stranded wire has always had a much nicer high end, and sounds cleaner overall than solid wire does. I think you'd be surprised to find out how soon skin effect really comes into play...even in the audio band. I'll have a look around for some papers I read a while back and post them here. There are wire designs based on the skin effect at audio frequencys
Also, PCB's don't have any gain by themselves....like wire they offer resistance, capacitance and even some inductance.......not quite sure what you meant there. I do know that in computers PCB's are nearing the limit of operating at all with extreme high frequency CPU's, and rarely will you see any PCB's in a microwave transmitter...except perhaps in the power supply, or control circuits. They simply cannot handle that exteme high of frequency very well. I wonder what PC manufacturers will go to when they reach the hf limit of modern PCB's?
Mark

Posted by Tim Reed (Member # 137) on 01-18-2003, 01:35 AM:

Mark, I'm fully in agreement with you on the solid wires. When I mentioned hearing a difference, I was referring to Monster Cable vs. THHN stranded. Sorry, I should've made that clearer.

Amen to skin effect. For the uninitiated, the closer you get to RF, the more it becomes a problem. The reason it's not a problem on PCB's is because the runs are so short -- millimeters, and flat (lots of surface area). Look at a television xmtr transmission line, those are big hollow pipes, because the energy travels along the outside.

In the early 80s, General Cinema had some brain in the home office that decided they'd save money by spec-ing solid wires for all conductors in new installations, throughout the building. They were blowing amps like no tomorrow, most of the surround speakers didn't work because of poor connections on the solid conductors. That's another thing; it's darned near impossible to get a good connection to the speakers with solid wire.

It nearly took an act of Congress to get this changed on subsequent plans, but I finally got them to.

Posted by Steve Guttag (Member # 268) on 01-18-2003, 08:38 AM:

For twisted wire...I either buy it as twisted wire (for common sources, Carol has it down to 12awg in red-black, WPW has it down to 10awg in white-black) or for shorter runs twist it myself.

It isn't glamerous to twist it but I do it by hand and don't take too long with it. If it is a long run it is a two person job to keep the free end from getting tangled as lay is formed.

Sure, I'd much prefer to make a machine to do it. My idea is to have the wire spools on a "ferris-wheel" like contraption which is attached to a disc (mandrel) with enough holes in it to align with the feed spools for the number of conductors in the cable (often only just two since speaker wire is the primary thing). You would thread the wire from the spools through the holes in the disc. From there the wire would be feed to a take up spool. The speed relationship of the take up spool to the "ferris wheel" will set the turns/inch. In this way you are twisting the conductors together without rotating them and stressing them.

I don't doubt that you haven't had any known problems (though I'lll wager there are measureable stresses in the cable now that affect its performance). Most techs I know use the drill method...with battery powered ones...it is just too easy to pass up. But it is wrong none the less. I can't endorse such a thing anymore than endorsing throwing film on the floor as a matter of threading up.

I have found that on most installations, the differences in cost of items like wire, are insignificant compared to labor costs. If I spent the better part of a day twisting cable, it would have probably been cheaper to have it done a facility with the proper equipment and had me working on something else.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 01-18-2003, 09:51 AM:

Steve,
Next time I need 24 - 200' runs of #10 twisted, we'll farm it out to you to have it done by hand [Big Grin]

!!
Mark @ CLACO
www.clacoequipment.com

Posted by Steve Guttag (Member # 268) on 01-18-2003, 01:14 PM:

Mark,

No problem...whom do I send the bill to [Big Grin]

Steve

Posted by Steve Kraus (Member # 476) on 01-18-2003, 03:23 PM:

And if you don't twist them and pull them as straight runs?

Posted by Steve Guttag (Member # 268) on 01-18-2003, 09:33 PM:

Steve K,

Like every good practice, twisting isn't necessary for a successful installation...I have often not twisted the wire pairs and never had the slightest problem, noise oscillation or otherwise. However, that doesn't make it right or the correct way. Given the choice, I'll use twisted wire every time. However...I am a stickler about it MUST be in grounded conduit so as to avoid picking up interference.

Steve

Posted by Steve Kraus (Member # 476) on 01-18-2003, 11:16 PM:

I'm just curious what anomoly you might expect to find. Twisting wire pairs carrying low level signals to cancel out crosstalk is a given. (That is actually done with different twist lengths among the various pairs.) I'm just not sure what could happen with power level audio frequencies. One thing is simply that twisting keeps the two wires together so I suppose we could consider three separate possibilities: (1)Twisted together; (2) held together in a pair but not twisted (say, bound with electrical tape every few feet; (3) just a bunch of wires in a conduit with no particular association between the wires that form a pair. What are the possible ramifications of each?

Posted by Gordon McLeod (Member # 33) on 01-19-2003, 11:12 AM:

The orginal purepose of twisting was to prevent the speaker lines acting like a giant antenna and the out put transitors becomeing a crystal radio set

Posted by Scott Balko (Member # 438) on 01-19-2003, 02:53 PM:

So just how many twists per foot is nominal? Speaking in terms a general 5 channel 1 sub system, do you want all the pairs to have a different twist rate? Can you run all speaker cables in the same conduit or should they all have a distance apart based on the output of the system?

Posted by Gordon McLeod (Member # 33) on 01-19-2003, 09:34 PM:

If they are twisted (usually 6 twists per foot) they all can run in the same conduit

Posted by Michael Schaffer (Member # 1204) on 01-19-2003, 10:21 PM:

Do you usually twist in pairs or would you twist all speaker wires into a thick bundle?

Posted by Daryl C. W. O'Shea (Member # 1303) on 01-19-2003, 10:24 PM:

Pairs.

Posted by Don E. Nelson (Member # 1049) on 01-21-2003, 02:50 PM:

An old friend who introduced me originally to Noel Lee, e-mailed me today and told me what my old room mates company , (Monster Cable) is worth.

$400 million. [Roll Eyes]

I guess somebody must be buying his wire! over-rated ot not.

He does at least let me buy his specialty cable by the 250 foot roll at his cost. [thumbsup]

]

Posted by Mark Gulbrandsen (Member # 72) on 01-21-2003, 07:47 PM:

Regardless of what a couple of people here might think is wrong, I will continue to twist wire the same way I have for the last 20 years. Those couple of people failed to provide any positive proof anyway, and they are obviously only going on their assumptions. Should any real proof be shown I might consider building a machine to twist it.....but it would certainly have to be pretty good proof. My twisting wire habit is based on the consistently good results that I, and alot of others have gotten from doing it.

Don, You also have to look at how much Monster spends on marketing....like McDonalds! Its a large amount of money, and their marketing department could market the Brooklyn Bridge and sell loads of them....gee, it would be a handy bridge to have around, and the Monster Bridge would always have smoother, more highly defined roadways too...... Monster stuff is ok, but there is actually alot better high grade cable out there available for much less money if you know where to look. It is good though that you are into using higher grade cabling. It can never hurt!!
Mark @ CLACO
www.clacoequipment.com