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Discussion Starter · #1 ·
Hi everyone.


In two days, I will be running speaker wires with in-line volume controls though my house. I want to know if it will be okay to run the speaker wire along-side electric. Or do they need to be spaced?


I will have 3 pairs of speakers, each with their own volume control. I plan on running in a home run manner. Most of the impedence matching controls I have come across work with even number pairs of speakers... will the fact that I have 3 speaker pairs matter?


Lastly, does anyone have any tips on this install? I know to zig-zag the wires. Am I missing anything? Any knowledge would be appreciated!


thanks
 

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I am assuming you are going to run speaker cables through the walls and attic or basement. First be aware that if you are in the U.S.A. in all likelihood you need to comply with some flavor of the National Electric Code (NEC). Most jurisdictions have electrical codes based on some year's version of this code, not necessarily the most recent one, along with their own specific requirements. You may or may not require a permit. Check with your local building inspector before starting. Even if you are not legally required to comply with the NEC, you should. It represents industry best practice for safety.


The problem with running speaker cables close to electrical cables is that speaker cables can pick up hum and noise from electrical cables through induction. The closer to parallel, and the closer together, the cables are, the more the speaker cables will pick up. The way to minimize this pick up is to place the cables as far apart as possible and cross as close to 90 degrees as possible when they have to cross. For all practical purposes, keeping speaker cables 6" from the electrical cables should be sufficient. The hum/noise should be inaudible. Using twisted-pair cable will help, too.


There is no reason to not run speaker cables in the same space as electrical cables as long as they are far enough apart.


The NEC has lots of restrictions on what you can do. You may not run the speaker cable through the same hole in a stud or plate as the electrical wiring. The speaker cable may not be supported by the electrical cable. The speaker cable may not come into the same box as an electrical cable unless there is an approved divider to keep them apart. The speaker cable used must have a UL CL2 or CL3 rating (applicable rating depending on maximum voltage). This cable has a jacket around the wires that helps protect the wires from damage as they are pulled through stubs, conduit, etc during installation, and will not easily propagate a fire. Installation must be done in a workman like manner (cannot just drop cable untidily on the rafters in the attic). And there are many more.


Architectural cable with a CL2 or CL3 rating may not be readily available locally. You can get it on-line at places like PartsExpress. They have 12 ga. twisted-pair architectural cable for about $.20/ft. Or you can by the equivalent Monster branded stuff locally or on-line for $1/ft. or more. FWIW there is not enough difference in geometry, materials and construction between brands in this stuff for any audible difference in the same gauge.


Now for volume controls...


If by impedance matching volume control you mean one that simply presents a constant impednace to the amplifier, regardless of the volume the speakers are playing at, you have a problem, the same as if you just wired the speakers direct to your amp. Assume you have 3 identical speakers with 8 ohm nominal impedance. You can wire them to the same speaker terminal in three ways: series, parallel, or two in parallel in series with the third one. The first two ways will result in all the speakers playing at the same volume. The third way will result in two speakers playing at the same volume and the third speaker playing much louder. So, we probably want to wire in one of the first two ways. Wiring in series will result in the amp seeing an impedance of 24 ohms. This won't damage anything. But the amp probably won't be able to put out full power into a load like this. Wiring in parallel will result in the amp seeing an impedance of 2.67 ohms. Most amps aren't designed to safely drive speakers with impedance this low. And the actual impedance will dip lower than this a some frequencies.


However, some volume controls can do more than just present a a constant impedance load to the amplifier. They can make the speaker look to the amplifier to have a different impedance than it really does. For example, if we make the speakers look like they are 24 ohms each, then connecting them is parallel produces a 8 ohm load for the amp. And some volume controls can do just that. Check out the Russound website or similar.
 

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Discussion Starter · #4 ·
Thanks for all the info!


Colm, I am working directly with the builder (my uncle). I am also talking to the electrician to look out for all respective codes and regulations. I posted on here so I would be loaded with info for my talk. Thank you for all points you brought up! I did not know about the rule against running speaker through the same hole as electric. It sounds like I wouldn't want to do it anyway, as it would be running parallel too often.


I won't be going into the garage, as I don't want to deal with firewall and special wrapped wire requirements.


Lastly, for the volume control: would this work?
http://www.hometech.com/audio/volume.html#VC5ADWI
 

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I cannot tell how this "automatic" impedance matching works from the literature. I do know it is possible to make the Russound products work by jumpering them for your environment.
 

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I wouldn't spend the extra $ on the automatic impedance matching....Use something cheaper, like:

http://www.smarthome.com/8262.HTML


As for doing the math, use the simple formula 1/R = 1/R1 + 1/R2 + 1/R3....etc.


You don't need a 3x setting to get 8 ohms with three speakers. Set two of the speakers to 4x (32 ohms) and one to 2x (16 ohms). 1/R = 1/32 + 1/32 + 1/16 yields R = 8 ohms.


Also, for general whole house audio, 12 awg speaker wire is overkill. 14 awg is more than sufficient, and less than 50', 16 awg is fine.


Robert
 

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Thanks for all great info, but what about running cables of the same category together. Can signal cables disturb each other? What about speaker cables?
 

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If you're referring to RG6 (video), Cat5 (phone/network) and speaker, then yes, you can run them together. The RG6 if dual or quad shield has sufficient shielding to resist any noise and the signals themselves won't generate any. Cat5 with its twisted pair construction will resist noise, and the digital info of data certainly won't produce any noise. Normal phone stuff generates some higher voltages for the ring, but still shouldn't induce any noise.


Robert
 

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Signal cables, low level interconnects, can be run together and even bundled together. They don't put out enough energy to cause a problem. Also, wires between amp and unpowered speaker will not pick up enough field effect energy from nearby power wires to be audible. You can test this by attaching a wire to a speaker and running it next to a length of equipment power cord. You won't hear a thing. Don't get overconcerned about such runs as long as code issues are met.


Do be careful with power lines and low level interconnects. For example, a signal line to a powered subwoofer that has an inaudible power line buzz on it will connect to the sub's amplifier. The amplification could make the buzz audible.
 

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Ok, then the signals should be ok. But I'm afraid that I was a bit tight-fisted when it came to speaker cables så I bought these. Am I doomed?


Edit: Sorry too fast on the submit button there... The speaker cables are 4 mm2 and unshielded.
 

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You'll be perfectly fine. Hardly anyone uses shielded or even twisted pair speaker cables.


Robert
 

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Ok, thx, the ht is very much under construction, but I promise that I will post some images when I'm done (hopefully sometime before christmas [some year ;)])
 
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