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Long Run Speaker Wire from Central Rack Question

post #1 of 4
2/24/13 at 3:40pm
Thread Starter 
I'm in the process of wiring a new home and have a question about both 'quality' of speaker wire and 'how' to wire. The essence of the question is this. I'm going to be using a centralized rack that includes Sonos Amps (or similar) running to multiple zones. Some of these zones will have four speakers in a single room (e.g. kitchen), so two left speakers and two right. The length of the wire running from the amp to these speakers is probably 70-80 feet once you go up/down/sideways. If that's the case, how should I wire rooms like this.

Option 1: run a +/- wire to each speaker individually (so eight wires going all the way back to the amp, two wires on each L/R, +/- terminal.

Option 2: run a +/- wire to the first right hand speaker and then run another 10 foot wire to the next right hand speaker. Do the same for L

Then to make this more complicated (which is why I'm very confused), what gauge wire would I need in each Option and should the speakers be wired in Series or Parallel.

I'm asking this in part becasue I just looked at the wiring the builder put in and it is wired as 16/4 CL2 to the room (about 75 feet), then split to the right hand speaker and left hand speaker, then another 10 foot wires each to the other right and left hand speakers.

I have the same situation in several other rooms that are far from the central rack.

Would love some advice as drywall going up soon.
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post #2 of 4
2/24/13 at 4:19pm
Hi Wjnog,

To the furthest speaker, you have 85 feet, or 170 feet round-trip. For 16 gauge wire, that would be about .7 ohms. If you wire two 8 ohm speakers in parallel, giving 4 ohms, then that .7 ohms is about 17% of your 4 ohms. If you wire the same speakers in series, then the cable is about 4.4% of your 16 ohms.

A rule of thumb that I've heard often, especially on this site, is that the cable should be less than 5% of the speakers impedance. You are just within that number if you wire in series, but well outside of that number if you wire in parallel.

You are using Sonos? But I thought that the beauty of Sonos was that the amps can be distributed around the house wirelessly.
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post #3 of 4
2/24/13 at 6:01pm
Thread Starter 
The Sonos decision is still up in the air. I'm having everything A/V go back to the central rack, and ideally would like to be able to put audio from cable/satellite into some of the in ceiling speakers as well, so may go with something different than Sonos. Main thing right now is figuring out what to do with this wiring before the drywall and insulation lock things in.

Your calculations above make me even more nervous. Does this mean when I read the wikipedia site or crutchfield site on speaker wire length/gauge, I should be doubling the distance? If so, I'm way off of 16 gauge.

I'm also a bit confused about the parallel/series wiring situation. I get the distinction when it is on the same wire, but does that mean if I'm running a separate wire back for each speaker, I wouldn't have as big of a problem (but maybe it is still a problem?)
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post #4 of 4
2/24/13 at 7:09pm
Hi Wjnog,

My answer was based on my interpretation that the builder had only run a single 16/4, so you would need to wire a pair of speakers together. Of course, it would give you more flexibility if he ran two sets of wire, so that you could reconfigure the speakers later. If so, and we again assumed 8 ohm speakers, then we're talking 9%, which is still above the recommended 5%.

Now, I don't know how important that 5% number is. We all understand that the added resistance from the cable will attenuate the signal some, but that in itself is not a problem. My understanding is that, as the percentage of cable resistance goes up, it will attenuate different frequencies more than others, based on the fact that a speaker's impedance varies with frequency. In other words, the increased cable resistance affects the speaker's frequency response. Of course, electronics that provide equalization can fix that, and depending on the speaker, it might not be an issue at all.

If it was my home, I would:
Do exactly as you are, with regards to a wiring closet.

Stick with the 16/4, but add another run so that each speaker has its own connections in your wiring closet. That will allow you to balance the volume later.

If I was really picky (which I am), I would have a system with EQ, and flatten the frequency-response and tune for the rooms.

As far as the Sonos is concerned, it is true that one of its strengths is wireless, and that they charge a premium for that. But their wireless controller might make it worth that premium, even if the rest of the system is hardwired. Personally, I hardwire whenever I can, but a wireless controller is a must. I'm currently setting-up my iPad as a controller for my myriad of Audiotrons. Maybe I would go with Sonos if I could bring myself to pay that much. Being cheap, I live at the trailing edge of technology.
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