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From: reid@glacier.ARPA (Brian Reid)
Newsgroups: net.audio
Subject: Re: wiring house for speakers
Message-ID: <3072@glacier.ARPA>
Date: Fri, 10-Jan-86 22:25:22 EST
Article-I.D.: glacier.3072
Posted: Fri Jan 10 22:25:22 1986
Date-Received: Sun, 12-Jan-86 07:43:13 EST
References: <2782@ut-ngp.UUCP>
Reply-To: reid@glacier.UUCP (Brian Reid)
Distribution: na
Organization: Stanford University, Computer Systems Lab
Lines: 74

A few years ago I wired my house for audio, and I learned a few things.

>Our system is by no means a high end audiophile system... , the system is
>quite satisfactory for us (although, as a regular reader of this net.group
>I am well aware that it is far from state-of-the-art!)

Your house will last a lot longer than your stereo. There is no reason not
to wire the house as if your stereo were the best; perhaps someday you might
change your mind or want to sell the house. As long as you're going to go
the trouble of doing it at all you might as well do it right.

>      I'm thinking of using something
>like 14 ga. or 12 ga. solid copper Romex.  Is this a reasonable choice 
>which will perform satisfactorily for *this* system?

I used 12-ga. Romex, 3-wire, and have never been sorry. It is a few cents a
foot more expensive and a bit more difficult to route through joist holes,
but it will handle anything. Because speaker voltages are lower than
household voltages, you actually need thicker wire to carry the same power
load.

Monster Cable doesn't work any better than 12-gauge Romex, but it is a
lot prettier, so if you are going to run a cable through the middle of your
living room you will probably want to use Monster Cable. As long as you have
the luxury of running the cable through the walls, then use Romex.

>Second, for those runs where the wire has to go a distance inside a long
>wall (as opposed to running in between ceiling joists) it would be convenient
>for me to simply use the same holes through the studs that the electrician
>would be making for his AC wiring in that room, thus saving me a 
>significant amount of time drilling separate holes for the speaker wiring.  

Because speaker wires are paired and power wires are also paired, the
inductive pickup at that impedance will be negligibly small (though
measurable). However, you might have some code problems if you aren't
careful.  According to my copy of the National Electrical Code, 1984
edition, Article 725, if you want to run speaker wires "in the same
enclosure, cable, or raceway" with power wires, then they must be considered
"Class 1 circuits".  This means that they must meet various fuse,
insulation, and transformer guidelines, and in general must be approved by
the electrical inspector.  Here in Palo Alto I talked to one electrical
inspector who said that if he signed off on my speaker wires as Class 1
wiring that would require me to have a re-inspection if I bought a new power
amplifier. I'm not sure that is true (the wording of the electrical code is
somewhat vague). I ran them as Class 2 wiring (more stringent requirements)
just to be safe.

If you don't want the stereo to have to meet Class 1 requirements, then they
are going to be called "Class 2 and Inherently current-limited". The code
for this kind of wire says "Conductors of Class 2 ... circuits shall be
separated at least 2 inches from conductors of any electric light, power, or
Class 1 circuits".

Summary recommendations, based on having done this and then lived with the
results for 3 years:

 * Run only the best wire. Your house is more permanent than your stereo.
   12-gauge Romex is good enough.
 * Run wires to more places than you think you will want. You won't have the
   opportunity to change your mind later, and you might want to move your
   speakers.
 * Use knurled binding posts, rather than RCA plugs or phone plugs, for the
   connection. The speaker wires will wiggle loose from the other kinds of
   connectors.
 * Use a different color Romex for the speaker wires than you use for 
   other house wires. At some time in the future you might want to cut into
   a wall to install a new speaker outlet, and it's nice to be able to tell
   the identity of the wires without cutting into them and measuring
   voltages.
 * While you're running wires, run 75-ohm coaxial cable lines into every
   room that has speakers. It's good for TV, FM radio, etc.
-- 
	Brian Reid	decwrl!glacier!reid
	Stanford	reid@SU-Glacier.ARPA