Stumped by question about speaker cables - need help

For as long as I can remember I've always ran 12 AWG to speakers at lengths of 20 ft or more based on "advice" from whatever gurus I could find.
Here's my problem, I was helping set up a friend's HT room in his house last night. He accidentally grabbed 2 rolls of 14 AWG instead of 12 AWG for his rear speakers. I told him point blank he's going to want to go back and get 12 AWG for the surround speakers that are further away (26 feet or so). He of course replies "Why isn't 14 AWG good enough?"
I couldn't give an answer better than "Because that's what I've always read and been told".

My understanding is 12 gauge was always recommended for lenghts in excess of 20 ft or so, because anything smaller would cause the sound to deteriorate along the way.

Could this not be compensated for by adjusting the level from the amplifier? Or does he have to make a trip back to the store to grab the right stuff?

What's actually happening to the signal at lengths greater than 20 to 25 feet in say a 16 AWG cable or 14 AWG that a 12 AWG eliminates? What goes on in that 19th foot that screws everything up in skinny cables???

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Originally Posted by kexodusc

For as long as I can remember I've always ran 12 AWG to speakers at lengths of 20 ft or more based on "advice" from whatever gurus I could find.

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Oh Ken - poor Ken - your dilemma is easily solved.
Those "gurus" - while well-intentioned I'm sure, are guilty of some gross exaggeration of what starts out as a kernel of troot and easily escalates into the absurd.

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My understanding is 12 gauge was always recommended for lenghts in excess of 20 ft or so, because anything smaller would cause the sound to deteriorate along the way.

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Of course there's a loss of efficiency - not sound quality but efficiency which, as you pose in your next question, can be easily rectified by merely increasing the gain to compensate for whatever losses might occur.

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Could this not be compensated for by adjusting the level from the amplifier?

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Yes!

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What's actually happening to the signal at lengths greater than 20 to 25 feet in say a 16 AWG cable or 14 AWG that a 12 AWG eliminates? What goes on in that 19th foot that screws everything up in skinny cables???

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That's my whole point, Ken ... nothing, absolutely, positively nothing gets screwed up (or down either). There will be no loss of sonic quality involved ... only a loss of efficiency, that's all there is to it. If the run was gonna be 150' or 100' or possibly even 50' then it might make sense to use the 12ga. Or, if the amp was being stressed by the length of cable to those surround speakers (a situation that I have a bit of difficulty even considering - then, it might make sense to use the 12ga. wire. But in nearly every situation that I've ever encountered, the "need" to use 12ga. wire simply doesn't exist.

Hope this settles your mind on the entire matter.

Ah, Woodman...how'd I know you were going to tell me that.
Then my suspicions were right. If I ever find myself in this situation again I'll know how to answer.
Thanks

Well, that solves one of my mysteries. A couple of years ago I moved my whole system to a larger room with the speakers much further apart and the only difference was that my receiver was running noticeably hotter. Didn't know why, and thinking back, I was using brand-name (i.e. thicker) speaker cables in the small room and cheaper higher gauge home depot zip cord in the larger room. Thanks for clearing that up.

Roger Russel, who is a real audio expert, gives a table for speaker wire gauges vs. length in the linked article.

http://www.roger-russell.com/wire/wire.htm

Unless your friend's speakers are very low impedance, then 14 gauge should be just fine. Rear speakers aren't so critical, anyway.