In-wall electrical for home theatre audio

Reply

  #1  
Old 09-05-15, 04:56 PM
Member
Thread Starter
Join Date: Sep 2015
Location: Canada
Posts: 13
In-wall electrical for home theatre audio

Hi all, I need a bit of help running wires to a few locations and have gotten conflicting info from a few electricians. I do intend to have the project all connected and finalized by a pro but want to know that I'm doing the right thing and not just buying into the audio purist snake oil on one side and the electrician's "don't worry about it" attitude on the other. I do have a lot of experience from work years ago in fishing all kinds of low voltage cable so figured I could run the AC wires myself. So thanks in advance to all that can help

I'd like to reference this article
Improving your Listening Room Wiring - By Vince Galbo
that states more or less

The single biggest goal in improving audio is to install heavier gauge wire using the following guide.

1 to 40 feet: 10 gauge wire
40 to 60 feet: 8 gauge wire
Over 60 feet: 6 gauge wire


as well as this one

Electrical Pre-wiring a Room for Audio and Home Theater | MartinLogan

The key to reducing hum and noise is to have the electrician wire only a single ground from the audio / home theater system to the electrical service panel

I also read that when calculating circuit load, I should calc 2 watts of power for every watt the amps were rated.


I have a 7.1 system that I need to run fresh AC wires for new Active in-wall speakers for the 4 rear channels. they are rated as requiring 20-200 watts at 1.75 amps and would be hardwired to an electrical terminal in a backing box.
Is the 10 gauge wire overkill and can they be all tied to 1 breaker?
What's with the single ground thing in the second article?
Can individual speakers go to a common junction box where it would go to the panel

While at it I could run wire for new receptacles for the front array that are freestanding but active also. the LCR trio are rated at 600VA and have 4x100 watt amps in each as well as a sub with 300VA. Can these reside on a single circuit without causing a power sag when in high demand?
Does the 10 gauge wire make sense? I wouldn't go larger

I would probably connect all front end and source gear as well as the Front Projector to the existing house receptacles in place

Thanks again
 
Sponsored Links
  #2  
Old 09-05-15, 05:31 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,968
Welcome to the forums! You have mentioned the 10 gauge wire, but you have not told us the overall length of runs for any of your raw electrical or speakers.
 
  #3  
Old 09-05-15, 05:34 PM
Handyone's Avatar
Forum Topic Moderator
Join Date: Aug 2000
Location: U.S.
Posts: 5,451
I can't help but just wanted to say thanks for the articles. Very interesting.
There are a few guys here well versed in audio and will probably get back to you.
The guys that wrote these articles are obviously purists and that's an understatement.

I'm interested in the grounding. 60 hertz hum is real, I experience it with my '65 Fender tube head and have read about ground loops and so forth, but how to put it in practice?
It'll be interesting to see some replies.
 
  #4  
Old 09-05-15, 06:12 PM
Member
Thread Starter
Join Date: Sep 2015
Location: Canada
Posts: 13
Hi, thanks for the replies and welcome.

I figure if I had to wire the front 3 and sub, the farthest receptacle would be about 70-80ft. wired directly to the panel and about 55-60ft for the farthest rear speaker. If they would go to a junction box, I could save about 25-30 ft. from each run before sending a ??larger cable?? to the panel. I know they mention going larger for the run but not sure about overkill.
There are no speaker wires involved, each speaker receives its individual signal from the preamp
 
  #5  
Old 09-05-15, 07:26 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: NJ - USA
Posts: 43,494
There are many things you can do to improve your setup. You can do a lot of reading, spend a lot of money and still have hum.

You can run a #10 circuit to your panel. It's connected to a 20A circuit breaker. You can bring that circuit into your audio room to a junction box and then split off with smaller wiring. #12 to each device would be more than adequate.

If you run a second circuit it needs to be on the same leg of incoming house power.
When you run a second circuit to the same equipment you can run into ground problems since now you have two ground wires to the panel. The propensity for hum is determined also by the equipment and how it's connected. One ground wire in one of the #10 circuits should be used for all the system grounds.



Brian.... power wiring has little to do with the hum in your guitar amp. That hum is caused predominately from the high gain amp stages needed to raise the guitar pickup to a usable level.
 
  #6  
Old 09-05-15, 08:25 PM
Member
Thread Starter
Join Date: Sep 2015
Location: Canada
Posts: 13
Thanks for the reply,
Spending loads of money on esoteric tweaks is what I'm trying to avoid and after reading the first article it made sense to me to beef up the power delivery further up the chain given I have 4 16" square holes cut out of my walls.
In its previous iteration, my 4 side & rear speakers were powered the traditional way of amp/speaker and I never had hum. obviously I don't want to introduce any but the goal of this exercise is to deliver the most clean power to the amps as possible.

So that I understand, You see no problem in having 4 wires going to the 4 speakers and joining up at an accessible box where they would be combined and sent to the panel. right?

Then If I wanted to do the front ones, I'd do the same for them.

The second article mentions a grounding method as well as your statement "One ground wire in one of the #10 circuits should be used for all the system grounds. "

Here is where I'm lost. Should the two junction boxes reside close to each other and the ground of one tied to the other without going to the panel? I'm no electrician but want to explain my wishes properly to one.

While on the subject, is the Front load of 2100VA not too much for a single circuit?
 
  #7  
Old 09-05-15, 09:06 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: NJ - USA
Posts: 43,494
If I were running two circuits to an audio system I would bring both circuits to one larger junction box.

2100va is a peak system value. It could be run on one circuit although two would be better.
 
  #8  
Old 09-05-15, 09:16 PM
Member
Thread Starter
Join Date: Sep 2015
Location: Canada
Posts: 13
Thank you so much for your help.

with the 2100VA split on 2 circuits and another one for the rears, I now have 3 circuits. Should this junction box be a small 4-breaker panel near the gear wired into one of my other 3 main house panels at one of their breakers.

Not being an electrician, some of the terminology escapes me.
 
  #9  
Old 09-05-15, 09:21 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: NJ - USA
Posts: 43,494
I didn't actually do a load calculation but three circuits sounds like an awful lot of power.
 
  #10  
Old 09-05-15, 10:05 PM
Member
Thread Starter
Join Date: Sep 2015
Location: Canada
Posts: 13
Hi, I mentioned 3 since ( after doing a lot of reading in the last two days) a 15amp breaker maxes at 1800VA and 1440 was considered it's safe limit. 2100 being too much I split it in 2. then took the 4 speakers rated at 350VA each for the rear total of 1400.

Still not sure what type of junction box, it seems the term is for simple connections, not separate breakers
 
  #11  
Old 09-05-15, 10:55 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: NJ - USA
Posts: 43,494
I was under the impression you were running #10 from the breaker to the junction box. You could at that point run #12 to your loads. You can use that circuit on a 20A breaker.

A good choice of junction box would be a 4-11/16 square.

Name:  4_11_16.jpg
Views: 192
Size:  18.1 KB
 
  #12  
Old 09-06-15, 05:50 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,361
Not a purist, but I have heard side by side systems wired with monster cables and also Cat 5 cable . I could not hear a difference. IMO, a lot is snake oil.
 
  #13  
Old 09-06-15, 08:16 AM
Member
Thread Starter
Join Date: Sep 2015
Location: Canada
Posts: 13
When I first posted this I hadn't really determined what I was running to the breaker yet nor to the speakers. I had a good idea as per the articles I cited but was and still am open to all suggestions. I'd hate to run wires just to have the electrician tell me I should have run everything differently.

Im still a little confused by this "One ground wire in one of the #10 circuits should be used for all the system grounds. " How exactly is this wired?

pcboss, I've been one of those guys that bought into the expensive cable and other and for the most part agree with you, not worth it but have come across certain products that have made a difference and not always the expensive ones either. I guess some are based more on accepted principles of physics, etc.. than others.

I actually bought a set of rubber style and point style isolators to put under source spinners and after a few weeks put them in a drawer as they brought nothing to the game then moved into another house and the sound in the room I chose was really congested. I tried the points and they made a dramatic difference.
 
  #14  
Old 09-06-15, 09:29 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,361
I see no point to installing wires one to two, or more sizes greater than needed. The stereo equipment has 15 amp cords. The circuits are limited to 20 amps maximum. Voltage drop in residential is not an issue. What do they think they are gaining by using oversized conductors?
 
  #15  
Old 09-06-15, 09:44 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: NJ - USA
Posts: 43,494
The oversized wiring from the room to the panel is supposed to reduce voltage sag under high demand peaks. Most people would never notice any sag since a home system is rarely used anywhere near peak levels.
 
  #16  
Old 09-06-15, 09:56 AM
Member
Thread Starter
Join Date: Sep 2015
Location: Canada
Posts: 13
Ok, so I should just keep it simple. The 3500VA used by all the amps are Peak Maximums. I should combine all of them in 1 junction box, send to the panel and be done with the second guessing, right? 15 or 20a?
 
  #17  
Old 09-06-15, 05:49 PM
Member
Join Date: Mar 2010
Location: USA
Posts: 2,858
deleted .......................................
 

Last edited by AllanJ; 09-06-15 at 06:14 PM.
  #18  
Old 09-06-15, 06:18 PM
Member
Join Date: Mar 2010
Location: USA
Posts: 2,858
Eaxh individual branch circuit as a cable or in its own conduit must have its own ground wire (equipment grounding conductor) going back to the panel.

All ground wires from all entering cables or conduits, including from different branch circuits, are tied together in each junction box or outlet box.

For wires run in conduits, at most one ground wire is needed including if several branch circuits share the conduit. The ground wire is sized to go with the heaviest wire branch circuit in the conduit. No ground wire is needed with rigid metal conduit, metal boxes, and certain styles of flexible metal conduit.
 
  #19  
Old 09-06-15, 10:14 PM
Member
Thread Starter
Join Date: Sep 2015
Location: Canada
Posts: 13
AllanJ thanks, I think the way you, PJ and others have described is how I will ultimately wire this up. fig.1 and fig.2 respectively in the second article ( pic. attached) reflect this. my confusion is really based in fig.3 which MartinLogan prescribe as superior. I have no clue what they could mean aside from riding a separate ground wire around the room ( kind of like bonding an in-ground pool ) but I don't think that would be acceptable as far as building codes go. I may be wrong but I read an article on here this week that said, no-no.
Name:  Screen Shot 2015-09-07 at 12.58.29 AM.jpg
Views: 160
Size:  20.4 KB
 
  #20  
Old 09-06-15, 10:47 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,361
Figure 3 would not,comply with the electrical code. The circuits must be grounded.
 
  #21  
Old 09-06-15, 10:53 PM
Member
Thread Starter
Join Date: Sep 2015
Location: Canada
Posts: 13
yeah, this is why I turned to the knowledgeable people here and included the article to have it translated to layman speak. The article seems to want this method used.
 
  #22  
Old 09-07-15, 04:36 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,361
All the grounds in the box will be tied together effectively making all the grounds have the same potential.
 
  #23  
Old 09-07-15, 07:35 PM
Member
Thread Starter
Join Date: Sep 2015
Location: Canada
Posts: 13
Ok boss, I get it.
let me ask, if I bring a second or third circuit into the room for the 2100VA at the from of the room, do "ground potentials" all have to match up or am I overthinking at this point?

G
 
  #24  
Old 09-07-15, 07:53 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,361
Since they would originate at the same panel I would think the grounds would be the same potential.
 
  #25  
Old 09-10-15, 10:03 AM
Forum Topic Moderator
Join Date: Sep 2005
Location: USA
Posts: 4,059
Coming into the discussion a bit late, but if it were my room, I'd probably wire each speaker to a box near the amplifier, then run the main circuit(s) to that box.

Electrically, it doesn't do that much, but it gives you future options if you want to split circuits differently, or possibly wire them into a surge protector/UPS. It also keeps all the grounds together, but in my opinion, it won't matter a bit.

In larger environments, ground loops and isolated grounds are an issue, but I can't imagine running into any kind of issue in a one-room residential setup.
 
  #26  
Old 09-10-15, 10:40 AM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,296
Agreed. No matter what you do in the house you're still on a residential pole pig transformer totally at the mercy of the power company. In a professional theater you would have an isolated transformer for the audio system(s) separate from the video, light systems or general building loads in which you could over size the transformer and conductors and ground it to your heart's content. It would also run you $200k+ to install it. In a residential service, everything in your house and about 10 or your neighbors' houses runs on the same lines and the same transformer, and guaranteed mid-summer that transformer will be operating at about 200% rated capacity.

Just use generally good installation technique, size the circuits well, and make sure everything is grounded to the same point. That's about the best you can do. Don't worry about spending a fortune on copper. The #10 is more than big enough -- the author's suggestion to use #8 or #6 is absurd outside of some professional studio with engineered plans. That's putting you into the realm of tenths or hundredths of percent of difference in performance on a overall general-purpose electrical system which is designed to run +/-10% of spec.
 
  #27  
Old 09-11-15, 07:07 AM
Member
Join Date: Nov 2007
Location: MI
Posts: 2,465
Otoh...

As a former audiophile--but too poor to continue--I will simply say that I have heard drastic differences that defy physics and explanations.
Examples include:
Running 10Ga main to feed an amp that uses a 14Ga detachable cord.
Detachable AC cords of identical gauge and length but varying wire stranding, purity and geometry.
High-quality small-value bypass capacitors in the power supply improving the audio quality.

Saying you can't hear the difference might possibly say more about you than the system.
I've found there's no point in debating because I'm a logical guy and I admit these things are totally illogical.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'