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Author: Dougaha Three stars, 500 posts Feste Award Nominee! Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 10469  
Subject: Re: Talk to me like I don't know anything Date: 10/6/2008 6:54 PM
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Mike,

OK, here we go. Wiring a house for multi-room audio is neither as simple, nor is it as complex as some would have you believe. It is a matter of putting in the right infrastructure for both current and future technologies. This involves a little bit of guess work, because no one truly knows what technology will do 10 years from now.

But I digress. The best way to wire a house for any kind of multi-room audio is to use the following guidelines:

*** Prewire phase ***

1. Home run all rooms to a central location, leaving room for potential growth by running the wires through a chase that will give you access to the storage closet from either an attic or an unfinished basement.

2. Do not run any of your speaker wire/RG6 coax/Cat 5/RCA wiring in parallel to any high voltage electrical lines, as this will potentially cause interference. It is OK to run perpendicular, but if you have to run parallel, keep 12-18 inches away. (Generally a full stud space). *** Plan your route before you pull the wire ***

3. The "feed" or "trunk" line to each room with speakers in it should consist of 2 wires, a 16/4 CL3 speaker wire (4 conductors to feed 2 speakers, and a CL3 rating for fire code inside walls), and a Cat 5 twisted pair. This allows for future expansion, as well as installation of optional keypads for a higher end system. It also allows for A-Bus, even though that's not my schematic of choice. If you use a keypad system for control, you can simply splice the speaker wire right behind the keypad (unless it's an A-Bus system, in which case the power to run the speakers comes from the keypad itself, not ideal). If you use a volume control (simpler and cheaper) you've got all your speaker wire right there behind it in the wall to terminate into the volume control. Use a p-ring on the stud to save your single gang space from drywallers. Something like this works well - http://www.grainger.com/Grainger/items/1XC32 (use drywall or wood screws to drive it into the stud).

Leave enough wire to work with so you can stuff it back in the wall during the trim phase. Usually about 12-18 inches will leave you enough spare for mistakes. (Yes, they do happen).

4. From the p-ring to the speakers, run a 16/2 CL3 speaker wire to each speaker location (some people run a 16/4 to the first speaker and splice a 16/2 onto it for the second speaker, works the same). You want to go up the same stud where your feed line is, so as to also avoid interference from electrical lines. Drill a 1/2" hole in the header at the top of the stud wall with a spade bit and run the speaker lines through it, being careful to stay above your ceiling joists. If you're doing ceiling speakers, some of them have optional rough in brackets that you can use to save your hole in the ceiling. I don't recommend using single gang junction boxes to mark your speaker location, as it forces you to stay too close to a joist, and the dog ears on the speakers can potentially run into the joist, preventing a solid grip on the drywall. If you don't know what kind of speakers you're using, take a piece of cardboard that spans the width of the ceiling joist where you want to put your speaker, and staple it to the joist. Poke a small hole in the cardboard, and leave about 12-18 inches of speaker wire hanging down. Your drywallers will probably paint over it, but at least you'll have enough that you can cut off what got painted.

This should get you through the prewire phase.

*** Trim phase ***

Next, we come to the trim phase. This is where you potentially put in your in-wall / in-ceiling speakers, in case you want the painters to paint them to match everything else. Be very careful to tell them to remove the speaker grills before they paint them. Most painters honestly don't care about your speakers, they're just trying to get a job done. Make sure they understand to remove the grills before painting, and DO NOT pain the speaker driver itself. (Trust me, it's happened before).


*** Finish phase ***

The finish phase is where you do all of your final installation and connections. This is where you have some time to decide on your control and distribution options. You need to decide on how you're going to handle the impedance load of 7 pairs of speakers. There are several different ways to do this. One is with impedance matching volume controls, another is with a device called an auto-former, and another way is with a speaker selector in the homerun storage cabinet. Here are the pros and cons of each. (I am assuming the house music is being run from the 2nd zone output of a new surround sound receiver. Make sure you connect both digital and analog wires from all of your devices that are connected into the receiver. That way you can hear each device in both the theater room and the rest of the house. You don't need 2 separate receivers to accomplish this).

Volume controls - installing an impedance matching volume control in each room, for each pair of speakers (using the p-ring as your gang box). This gives you local volume control in each room, and it's also a good way to handle multiple pairs of speakers (more than 4 pair). However, once you go beyond about 4 pairs, you really start to lose power per room. You can solve this problem by using something like a 6 channel or 12 channel amplifier off of the 2nd zone output (RCA connections) of your surround sound receiver, and using the jumpers on the volume controls to keep it down to something like 2x or 4x to keep the power a little higher. (The cons of this are that if you don't know what you're doing, you can easily burn up your amp and volume controls with incorrect impedance settings).

Auto-former - this is a device that automatically transforms (thus, autoformer) the the impedance load of multiple pairs of speakers into a single 4, 6, or 8 ohm load into an amplifier. Typically they can handle up to 10 pairs of speakers at once. Something like the Niles SMS-10 (http://www.nilesaudio.com/product.php?prodID=SMS-10&reco...) is what we use. This is typically used in a commercial environment (sports bars, etc) where many, many speakers are hooked up to 1 amplifier. This is not a really good solution for most residential applications, as it gets messy with all the wires / terminations, and most people get intimidated by the setup.

Speaker selector - the simplest method of impedance matching, typically you can get up to 6 pairs on a speaker selector. The con of this is that you don't get discrete volume or control locally within a room. There are speaker selectors with volume controls, such as this - (http://www.nilesaudio.com/product.php?prodID=SSVC-6&reco...)

*****************


Anyway, Mike, I hope that helps. That's my best effort on little to no sleep after vacation. Let me know if you have any more questions.


Doug
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