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Author Topic: Speaker wire gauge question Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 04-11-2010 08:40 PM                     I usually use 10 gauge wire for Subs. I am upgrading an auditorium that previously had no subs but has one extra pair of 12 gauge wire running from the booth to the stage. The auditorium is 55 feet long so the wire run is about 75 feet. I will be using two 18" subs hooked in parallel. Can I get away with using the one pair of 12 gauge wire? Or should I go ahead and run a new line?  |  IP: Logged Mike Blakesley Film God Posts: 12767 From: Forsyth, Montana Registered: Jun 99 posted 04-12-2010 10:57 AM                        We have dual 18" subs and all our wires are 12 gauge (as recommended by Mark G.) and we have had no problems. We have one set of 12 gauge running both of the subs.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 04-12-2010 02:26 PM                        The bigger the better. If you run at low volume, it may be OK. At high level, you could be drawing signifiant current on the speaker wiring. I would view 2 18" on one pair of #12 as a bit skinny. Typically, I use #10 and put one 8 ohm, 18" on 2 wires, the other one on another pair. The issue here is damping factor; how the speaker talks back to the amplifier. Safety/fire are not a concern. Louis  |  IP: Logged Robert Minichino Master Film Handler Posts: 350 From: Haskell, NJ, USA Registered: Dec 2005 posted 04-12-2010 03:09 PM                        A higher damping factor just causes the speaker's effective Q to rise a little, resulting a slightly raised response around resonance. This is a minimum-phase phenomenon, so it can be corrected with equalization.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 04-12-2010 06:35 PM                     Isn't this a bit silly? Tom has #12, he should try it and see if it works effectively for him. Does anyone think differently? --jhawk  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 04-12-2010 07:22 PM                        If it doesnt work out for him then maybe he could use the 12 gauge wire to pull in the new 10 gauge through the conduit.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 04-12-2010 08:49 PM                     I'm a bit more pragmatic about it. How long is the room...lets presume 50-feet, for now though that may be a bit long given the estimated 75-foot cable run. But given a 50-foot room, one needs over 2000-watts to drive a double 18" subwoofer (typical) to the required level for digital (113dB). Doing the math, one finds that while the subwoofer is being driven to such a power, into 4-Ohms (presuming the 18" drivers are wired paralleled), you need 22.69A on that #12awg cable during that moment in time. Bzzzt...it is a bad design. Now, it can be argued a great many things. The 22.69 is a VERY rare occurrence as most sub tracks do not hit the max and when they do, it is not sustained. The next question is, is the volume running at 7.0 on a properly calibrated system? Odds again are probably no. Lastly, is the amplifer in this system actually capable of the required 2060-watts and if the answer to that is "yes" are the subs capable of handling that power...the answer is likely "no." Now, if you are not running digital audio (film or DCinema), then things get much easier and 12awg is fine for the current load. For digital, I would say that 10awg should be the minimum in this set up or two pairs of 12awg. -Steve  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 04-13-2010 04:46 PM                     I'm with Steve. It is hard to say "let's try and see if there is any problem" since it may work for a while and then fail. Or it may work without breaking but without the best result that sometimes is not easy to identify by ear. Someone could say "if I do not notice by ear, why bother?". I would say "since we are doing it, let's do it properly". Cheers Marco  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 04-13-2010 10:37 PM                     Marco, I would agree...I'd rather do it right the first time. Thanks everyone for your suggestions.  |  IP: Logged

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