True. If you have control over the situation.  Or if you're a trainee or other person who has not been trained to think your way out of a stupid situation that someone else created.

If you've somehow GOT to get three channels of audio somewhere and you only have four conductors, then that's what you've gotta do.  All the reasons not to do it have been offered.  It's like using CAT5 for speaker wire -- never design to do it, but if that's all you've got, then use it and cope.

I suppose it would have been worthwhile to ask, why would you do this?  I don't remember that being mentioned.

If you loosen up the question a bit, you could sure get three channels of audio over four conductors; use resistive dividers at the far end to drop the signals to line level, thus drastically reducing the current flow through the common wire that goes back to ground.  Then you'll need power amps out there, of course, but hey -- it gets the signal there, and cleanly.

We could pontificate the various science projects all day long.

The answer is to spend that money banging a hole in the goddamn wall, pulling the correct wires, then paying a professional to patch and finish the access spots we opened.

$500 does not go very far when it comes to adding amps down the chain, paying engineering and design time to someone who has any real engineering experience to create a bespoke solution.

That same $500 goes a long way in patching and painting a few holes.

And at the end of the day, you can sleep soundly knowing that some goofy lab theory bullshit does not start a small campfire in the equipment location or put an amp into DC and send a giant sustained signal down the line and start speakers on fire throughout the house.

For the people that want to know, the reason is fairly straightforward: only 4 conductors existing at a proposed LCR passive soundbar location.

The reason I asked was to get expert opinion on feasibility. In the past I have seen audio circuits that made me think it was not that far out of the ordinary to accomplish something like this. A good example is car audio where only one conductor goes from the amp and the chassis ground is used at the speaker location.

I'm certainly not interested in skating a project by with inferior methods, creating additional service calls, or putting anybody's home in danger (not sure if that one is valid?)

The resolution is that there is a CAT5E close that can be used. The alternative is to start demo'ing a cultured stone fireplace as well as a ceiling. Would like to but realistically not going to happen. The speaker is a Snap LCR, so not high end but a decent speaker. If there are real-world issues with the sound, we can revisit the option to retrofit additional wire.

(Eyebrows go up) How would that be? As a speaker wire? An additional common?


It might sound okay.

Now, here's a question: since it's a sound bar that isn't, oh, eight or ten feet wide, we can't be worried about how wide the sound stage is, and how beautifully centered the center is. How would it sound if you didn't connect the center, but instead used four conductors for the left and right, and told the AVR that there is no center speaker?

Yep that's what I'd do. I doubt it will make much of a difference with that kind of speaker and setup. If you feel guilty hook it up in stereo, do a demo. Then run another pair across the floor and do another demo with same content. See if they can tell the difference, and if they think it's worth it get out the sledge hammer...then see if they still think it's worth it.

I certainly thought about setting up for phantom center. I guess the thing to do is do an A/B comparison as mentioned.

I had to do this exact thing on a take over job that was wired by an electrician.  It was a 5.1 suround system wired to a central rack located on another floor.  The sub was inwall and wired properly back to the rack with 14/2, but there was only a single 14/4 from rack to the TV location.  To make it even worse, the rear surround speakers were wired to the TV location and not back to the rack so then I needed to connect 5 speakers with only 4 conductors.

AVR was a Denon 3311CI so I ran it past Matt who checked and said that all grounds were common in the chassis and ended up using the 14/4 to connect the front LCR speakers by sharing one conductor for the ground.  For the rear surround speakers, I connected them to two available RG6 that ran back to the rack (yes... RG6).

It's a cluster duck, but it's been working fine for over 2 years.  If it's too a big a deal to re-wire, thought you might appreciate and example of this actually working without starting fires or creating a hole in the space time continuum above your jobsite. :)

OK, they're common AND at chassis potential. Better?

Re: the car stereo using the car's body as a conductor- that doesn't work if a power amp was used. A power amp would shut down or oscillate if you ground the speaker negative. A low powered head unit can be wired this way and if you measure from the speaker ground WIRE to the radio's case, you would find there's no appreciable resistance.

Who wired it this way? If it was your company, it's time to bend over and take it for not planning this better. If it was someone else, be diplomatic and professional, saying that the way it was wired didn't leave an opportunity to use a LCR speaker in the correct way and that for future system changes/current system reliability and sound quality, another pair of conductors is needed.

It was homeowner wired a few years ago when the house was built. I forgot to mention its a real log home too, so new wiring is quite difficult.

Alas, that is the question. My experience at schematic level is that many if not most current surround sound avrs are not common ground nor are the speaker grounds at chassis potential. That would be my basis for hesitating on a "let's see if this works - OK it seems to work, let's see how long it lasts" basis.

For me - sound bar with left and right only; phantom center.

As noted earlier, the soundstage from three speakers no more than three feet apart is not a real factor.

I Think some of you are very attached to the protocols. If you measure continuity with a multimeter between your negative poles in the amp end or in the LCR end and it gives you a true value, than it will definitely work. Of course, like a few mentioned, you will be sharing one conductor between 3 speakers, and you will loose power, but i have no doubt that it will work. Specially because i have done this several times in retrofits. And yes, i have used Cat-5 for speakers, Coax and Cat-3 telefone cables for IR too. would you rather stick to the industry's protocol or make it work with what you got?

Huh? What does that mean?


Your basic idea is correct but your nomenclature needs some cleaning up. I mean, ten ohms is a true value, and that would or should scare the hell out of you in re doing this. You could also measure a "true value" indicating that there's a semiconductor or two between the grounds. That would predict disaster.


Interesting. Here you don't specify that it will work IF you measure zero ohms between negative poles. You should have doubt that it will work if all three channels are BTF outputs. The fact that few are BTF should not be ignored, but determined by measurement of looking it up.


These are not at all exclusive of each other. It is proper and best to stick with the protocols because they guarantee that things will work. And think of this -- ten years from now you go back to a client and you know how it's wired because you have used the same protocols for all that time. I've seen it -- I've done it. It's incredibly valuable and gives you a great advantage over any other integrator.

The other side of the coin is that you aren't a good integrator if you can't make it work with what you've got when you have limitations such as this. Now, if there were only two conductors, only mono would be possible, so there are limitations that cannot be overcome even by the best of us. Learn to invent a new way to do things when you're presented with way less than the protocols tell you to do.

Ernie, you are right indeed. What i am trying to say is that if you don't have any other option ( besides turning the customer's house into a swiss cheese ) would you rather make it work even though is not the appropriate way to do it, or would you turn around and say it's not possible and frustrate your customer? another company will come, make it work and they will think you have no clue on what you are doing. At least that is how i Think

yes.