Electrical receptacles for my home theatre - what should I install? - Page 2 - AVS Forum
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post #31 of 52 Old 07-30-2012, 09:14 AM - Thread Starter
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Hey folks,

I really need some advice now on audio/video cables... so all of my AC receptacles were wired up and positioned directly behind where my system rack and subwoofer will end being placed (that's the idea right? put it behind and out of sight). The dilemma now is all the in wall AV cables I need to run. I wanted to have wall mounted binding posts for the front 3 speakers and an RCA line out wall plate for the sub. I went out and bought already a nice 7.1 dual wall plate which all the in-wall speaker and sub cable will tie into directly behind the system rack. Everything will look nice & sharp. Well my issue now is where do I place the 7.1 audio plate (for the amp) and the line out for the sub? I never gave it much thought but I had intended to place these plates right next to all the AC receptacles I have. Last night I started to wire up the sub - I placed a receptacle box on the other side of the same stud that has the AC receptacle (for the stub). The RG6 I ran is in parallel to the AC cable - there's nothing I can do about that - but i made sure to separate them by a good 1.5 feet. I didn't finish this run b/c I'm having doubts about where to place the receptacle for the 7.1 mater wall plate. I've got 4 AC oulets fasted to the same wood stud behind my component rack - two on one side and two on the other (yes I should have used a double or triple box). Anways I'm looking at where I was going to place the box for the 7.1 plate just above these AC outlets and am thinking how am I going to avoid crossing my audio, cable, and sub wires with all the AC lines & boxes that are already there? Also, how much distance should I or do I need between AC receptacles and other wall receptacles for cable (video) or speaker wire? Can they be at the same level on opposite sides of the same stud, or above or below each other on the same side of one stud?

I was reading some other threads about "code violations" (I presume in the U.S) for running high voltage and low voltage wires to close to each other... I think. I don't quite understand the exact requirements and am trying to determine the codes up here in Ontario/Canada... but how the heck do other people plan their positions for AV and AC outlets? I want everything to be within the same 16" frame because when my component rack goes there I want it all behind and concealed. The rack isn't going to be very high either so I won't have too much room to place between the AC outlets and the outlets for the speaker and video cables (and sub). Can I have an AC outlet fastened to the left side of a stud and an outlet for cable fastened to the right side at the same height? As for speaker wires I don't see any way around running my mains in parallel with the AC lines inside the studs... I'll be sure to keep a good distance between them, but is the practice to buy twice (or 3x) the length of speaker wire to pull it straight up to the ceiling, across, and then all the way down to each point to avoid running it in parallel with AC cable?

I envisioned having all my wall plates (AC, audio, video) clustered nicely together in the areas where my TV, AV rack and subwoofer will end up being placed. Now I'm reading all this stuff and wondering if I'm going to need to scatter wall plates all over the freakin walls to avoid parallel wiring and interference from AV boxes being too close to AC boxes :S

Does anyone know what the law/code for their region specifies and what people do in practice?
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post #32 of 52 Old 07-30-2012, 09:22 AM - Thread Starter
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If you scroll down to the last picture on this page its not too far off from what one area of my wiring was going to look like:
http://www.bennedum.org/ht/Wiring/

Thought this was the idea/goal... Will the speaker wires pick up interference from the AC outlet being that close (what if it was closer than pictured here?). What if those speaking wires and AC cables are physically touching behind the walls - 1) is that a violation and 2) will that effect the audio?
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post #33 of 52 Old 07-30-2012, 01:48 PM
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Quote:
Originally Posted by stuckin96 View Post

Does anyone know what the law/code for their region specifies and what people do in practice?

Try this link:

http://lanecoburn.com/images/BN_Sept-Oct07.pdf

and read down through the paragraph heading "Design for Proper Separation of Cables" and as far beyond that as you think you need to.

One other thing - binding posts are stone age techology with lots of practical problems. The professional solution is called "Speakon" and can handle the connections for up to 4 independent speakers in one connector. This is handy if the wife wants to disconnect things to clean.

http://en.wikipedia.org/wiki/Speakon_connector

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post #34 of 52 Old 07-30-2012, 04:08 PM
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Just to clarify, homes wired with 240/120 panels are all on a single phase. The home's panel is a SPLIT single phase.
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post #35 of 52 Old 07-30-2012, 05:11 PM
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Quote:
Originally Posted by stuckin96 View Post

Does anyone know what the law/code for their region specifies...?
You might want to do searches on "Ontario Electrical Safety Code" and "Canadian Electrical Code".

FWIW Candian practice should be quite similar to that of the USA. They try to harmonize their codes.
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post #36 of 52 Old 07-30-2012, 05:14 PM
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Quote:
Originally Posted by stuckin96 View Post

I was reading some other threads about "code violations" (I presume in the U.S) for running high voltage and low voltage wires to close to each other...
You can run low and high voltage close to each other. The restrictions are within junction boxes and raceways. You cannot run them in the same one without an approved divider. Low and high voltage in the same stud bay is not a code problem. Just don't run them through the same hole in a stud or plate.
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post #37 of 52 Old 07-30-2012, 06:05 PM
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You can run them NEAR eachother anywhere but code states not in the same raceway or holes.

so the hole you drilled for your recepts cant have low voltage wires in them but you can drill a hole right next to your high voltage and even staple right next to the high voltage
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post #38 of 52 Old 07-30-2012, 06:58 PM - Thread Starter
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Appreciate the suggestions and links. So from a code perspective I'm okay (the AC cables are run on their own through the studs). The first RG6 cable I started to run last night - and the speaker wire I was planning to run - do not/will not come into physical contact with any of the AC cables. But my concern is having metal receptacle boxes for the speaker posts, sub line out, and the 7.1 connection in such close proximity to the AC receptacles. As I said I originally planned to place these boxes on the other side of the studs that have the AC boxes on them. In the case of the 7.1 box that was going to go right above an AC outlet on the same side of the stud (we're talking a few inches).

I've since been reading that speaker cable in particular is not typically effected by interference emanating from nearby AC power cables. It seems the sub woofer cable is very prone to interference. Last night I had this sub cable (using RG6 in case nobody followed) at least 1.5 feet away from the AC cable, except where I terminated it in a metal receptacle box on a stud that had an AC receptacle directly on the other side at the same height. Someone today suggested I GROUND the receptacle box for the sub cable - literally connect that box to the ground screw inside the AC receptacle right beside it (?).

Am I making too big a deal out of this or not? Originally I thought someone taking a first glance at my wiring/grouping would commend the clean layout and thoughtful (ha!) distribution/placements... Now I'm worried about Frankensteining my theatre room and the first person looking to buy my house years down the road is going to take one look and say this all has to be torn out and rewired b/c my AC outlets are way too close to all the A/V outlets. Obviously if its going to sound like crap (hissing & popping) that's going to be a total disaster :S
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post #39 of 52 Old 07-30-2012, 07:18 PM
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You mat be worrying too much but if you can keep them away from ac lines
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post #40 of 52 Old 07-30-2012, 07:51 PM
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Quote:
Originally Posted by stuckin96 View Post

I've since been reading that speaker cable in particular is not typically effected by interference emanating from nearby AC power cables.
So, don't worry about it. Generally, anything it picks up will be lost in the noise floor.
Quote:
It seems the sub woofer cable is very prone to interference.
Primarily 60 Hz hum. The best you can do is avoid runs parallel with the AC as much as possible, keep as much distance from it as possible when you do have to run parallel, minimize cable length, and use a cable with 95% copper braid shield, or better yet dual 98% copper braided shield.
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post #41 of 52 Old 07-31-2012, 05:09 AM
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Quote:
Originally Posted by stuckin96 View Post


I've since been reading that speaker cable in particular is not typically effected by interference emanating from nearby AC power cables.

At least 3 reasons:

(1) Big signal voltages
(2) Low impedances at both ends
(3) Floating (ungrounded) differential line receiver.
Quote:
It seems the sub woofer cable is very prone to interference.

I presume you mean the line level (RCA) cable from the subwoofer output of the AVR or equivalent.

Reasons:

(1) only nominal signal voltages which can be too low if the gain control on the subwoofer is not properly adjusted. Set it as low as you can and still have good dynamic range.
(2) Medium impedances at both ends
(3) Grounded, unbalanced, single-ended line receiver.
(4) Load by nature has lots of sensitivity at the same frequency as power line hum.
Quote:
Last night I had this sub cable (using RG6 in case nobody followed) at least 1.5 feet away from the AC cable, except where I terminated it in a metal receptacle box on a stud that had an AC receptacle directly on the other side at the same height. Someone today suggested I GROUND the receptacle box for the sub cable - literally connect that box to the ground screw inside the AC receptacle right beside it (?).

One safety rule is that everything metal that you can touch should be connected to safety ground.
Quote:
Am I making too big a deal out of this or not? Originally I thought someone taking a first glance at my wiring/grouping would commend the clean layout and thoughtful (ha!) distribution/placements... Now I'm worried about Frankensteining my theatre room and the first person looking to buy my house years down the road is going to take one look and say this all has to be torn out and rewired b/c my AC outlets are way too close to all the A/V outlets. Obviously if its going to sound like crap (hissing & popping) that's going to be a total disaster :S

Safety first.
Looks second.


However, a safe installation often just naturally looks good.
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post #42 of 52 Old 07-31-2012, 08:17 AM - Thread Starter
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Quote:
Originally Posted by arnyk View Post

I presume you mean the line level (RCA) cable from the subwoofer output of the AVR or equivalent.
Reasons:
(1) only nominal signal voltages which can be too low if the gain control on the subwoofer is not properly adjusted. Set it as low as you can and still have good dynamic range.
.

Just clarify: gain control on subwoofer is what - the volume knob (on the sub?). What about the gain (db adjustment) from the receiver? Are you suggesting I turn the volume knob at the back of the sub lower and increase the db level (+5, 6, etc) for the SW channel from the receiver?

I was down there late last night doing some wire runs and although the speaker wires all converge in the double receptacle box directly above an AC receptacle I managed to route them above and around the AC lines. As for the 12' RG6 cable I'm using for the sub, it crosses an AC cable at 90 degree with at least a few (4-5) inches in between and then runs parallel to an AC cable for about 6-7 feet with almost (maybe more than) 2' separating them. The closest the RG6 cable gets to any AC cables is where it terminates at the receptacle boxes at either end, which both have AC receptacles immediately beside them (other side of stud). I think I'm going to take yours and people's advice and ground both metal receptacle boxes I've installed for the 7.1 convergence plate and the sub out.

Thanks for all the suggestions. I'm feeling better now.

PS - final thought: is there any materials that work well to lessen the effects of interference between cables? I can't help notice that throughout my basement's ceiling any place the builder routed AC cables close to water pipes or other wires/pipes between the ceiling joists they stuffed handfuls of insulation between them. Would sticking insulation, excess pieces of drywall, or any other material between AC cables and AV cables make a worthwhile difference?

Cheers. I'll have to post a pic of the place one complete (1 shot when its complete but empty, and another shot with all my gear in place).
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post #43 of 52 Old 07-31-2012, 08:32 AM
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Quote:
Originally Posted by stuckin96 View Post

PS - final thought: is there any materials that work well to lessen the effects of interference between cables?

Air, crossing at 90 degree angles, proper shielding

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post #44 of 52 Old 07-31-2012, 09:48 AM
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Would sticking insulation, excess pieces of drywall, or any other material between AC cables and AV cables make a worthwhile difference?

No.

Thick steel or mumetal will, but are unecessary and expensive.

Just something to think about. All of your equipment that uses electricity have AC conductors running very close to the signal carrying conductors.
Cable TV and Telephone signals are carried on the same poles as 13KV feeders.
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post #45 of 52 Old 08-01-2012, 04:27 PM
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Originally Posted by SAM64 View Post

No.
Thick steel or mumetal will, but are unecessary and expensive.
Just something to think about. All of your equipment that uses electricity have AC conductors running very close to the signal carrying conductors.
Cable TV and Telephone signals are carried on the same poles as 13KV feeders.

Yepper, .... and what are they seperated by? .... A very strictly designed air space.

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post #46 of 52 Old 08-01-2012, 05:54 PM
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Quote:
Just something to think about. All of your equipment that uses electricity have AC conductors running very close to the signal carrying conductors.
Cable TV and Telephone signals are carried on the same poles as 13KV feeders.

You are understating the facts. I frequently see cellphone base station antenna bays mounted on the same towers as 200-400 Kv lines.

This is apparently not without severe costs:

http://www.jmpee.org/jmpee_site/Vol_44(2)/JMPEE44-2-88Huertas.pdf

"Experimental tests results show that the presence of 400 kV electromagnetic field creates a radio interference, which is coherent with the model proposed by the BPA. Moreover, it was found that the BER is independent of ambient temperature and relative humidity for both cases: tests with the 400 kV power lines energized and no energized. It was concluded that the presence of the 400kV lines reduce 70% the wireless data transmission distance."

However the mechanism that causes these losses is corona due to the extremely high voltages, which would not be a problem with the voltages in just about any piece of audio gear.
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post #47 of 52 Old 08-02-2012, 07:06 AM
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You are understating the facts.

And you are, once again, completely missing the point.
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post #48 of 52 Old 08-02-2012, 08:10 AM
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And you are, once again, completely missing the point.

Please explain.
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post #49 of 52 Old 08-02-2012, 11:19 AM - Thread Starter
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Originally Posted by arnyk View Post

Please explain.

How about what you said regarding subwoofer gain: "only nominal signal voltages which can be too low if the gain control on the subwoofer is not properly adjusted. Set it as low as you can and still have good dynamic range".

What exactly did you mean by setting it as low as you can - the subwoofers own volume control (knob at the back of the sub), OR did you mean the channel output level (+/-DB) set from the receiver?
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post #50 of 52 Old 08-02-2012, 11:30 AM
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Quote:
Originally Posted by stuckin96 View Post

How about what you said regarding subwoofer gain: "only nominal signal voltages which can be too low if the gain control on the subwoofer is not properly adjusted. Set it as low as you can and still have good dynamic range".
What exactly did you mean by setting it as low as you can - the subwoofers own volume control (knob at the back of the sub), OR did you mean the channel output level (+/-DB) set from the receiver?

The basic idea is to run the interconnect at the highest signal voltage reasonably possible in order to minimize the audibility of noise.

I meant set the gain on the sub as low as you can without forcing the voltage from the receiver so high (to get proper volume of bass) that it is distorted.

I've seen people complain about hum from their subwoofer, and it turns out that the gain on the sub is all the way up. If they back it off a reasonable amount and make up the loss with more gain on the receiver's sub output, then all might be well.
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post #51 of 52 Old 08-02-2012, 12:52 PM - Thread Starter
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Quote:
Originally Posted by arnyk View Post

The basic idea is to run the interconnect at the highest signal voltage reasonably possible in order to minimize the audibility of noise.
I meant set the gain on the sub as low as you can without forcing the voltage from the receiver so high (to get proper volume of bass) that it is distorted.
I've seen people complain about hum from their subwoofer, and it turns out that the gain on the sub is all the way up. If they back it off a reasonable amount and make up the loss with more gain on the receiver's sub output, then all might be well.

OK that's what I thought you implied but I wanted to be sure. So instead of having the sub volume nob set at 3/4 and the receiver SW channel at -2db, I should try lowering the sub volume knob to (example) 1/4 and set the receiver SW channel level at +6/+8db. Will keep that in mind when playing with it.

Small update: I have grounded all the metal receptacle boxes that will house the speaking, sub/audio, and video/coax wall plates for good measure.
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post #52 of 52 Old 08-03-2012, 11:17 AM
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Quote:
Originally Posted by arnyk View Post

The basic idea is to run the interconnect at the highest signal voltage reasonably possible in order to minimize the audibility of noise.
I meant set the gain on the sub as low as you can without forcing the voltage from the receiver so high (to get proper volume of bass) that it is distorted.
I've seen people complain about hum from their subwoofer, and it turns out that the gain on the sub is all the way up. If they back it off a reasonable amount and make up the loss with more gain on the receiver's sub output, then all might be well.

+1

Many misunderstand this ....
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Originally Posted by stuckin96 View Post

OK that's what I thought you implied but I wanted to be sure. So instead of having the sub volume nob set at 3/4 and the receiver SW channel at -2db, I should try lowering the sub volume knob to (example) 1/4 and set the receiver SW channel level at +6/+8db. Will keep that in mind when playing with it.

Arny gives good advice, you got to get the signal up out of the noise for the interconnect run (the vulnerable point), as the next stage of amplification amplifies each (signal and noise) accordingly.


Good luck

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