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Author Topic: Speaker wire gauge Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 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.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 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  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 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  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 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  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 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  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 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.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 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  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 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 !! Mark @ CLACO www.clacoequipment.com  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-18-2003 01:14 PM                     Mark, No problem...whom do I send the bill to Steve  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 01-18-2003 03:23 PM                    And if you don't twist them and pull them as straight runs?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 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  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 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?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 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  |  IP: Logged Scott Balko Expert Film Handler Posts: 136 From: Redwood Falls, Minnesota, USA Registered: Apr 2000 posted 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?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 01-19-2003 09:34 PM                     If they are twisted (usually 6 twists per foot) they all can run in the same conduit  |  IP: Logged

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