Speaker wire & conduit

[Dain Bramaged]

For new home theater construction - electrically speaking - would there be any benefit in running the speaker wires through conduit to help keep the EMF unwanted signals from other wiring from inducing a signal in the speaker wire ?

[Danny]

I think so, when running data cable near electrical cabling there needs to be 100mm between cables or run one of the cables through conduit. Not sure about the effects on speaker wire but i'm thinking close proximity to a electrical circuit may introduce a hum.

[brucek]

would there be any benefit in running the speaker wires through conduit to help keep the EMF unwanted signals from other wiring from inducing a signal in the speaker wire ?

A speaker connection is a very low impedance circuit and as such is not a candidate for crosstalk problems. Notice that you don't need any shield on these cables? It takes a very large signal to induce noise in a speaker wire connection and isn't susceptible to outside interference. You could arc weld over a set of speaker cables and not have to worry........

brucek

[Dain Bramaged]

Ok. Thanks.

In the past I’ve had problems with fluorescent lights inducing noise but I didn’t take the time to trace down which part of the system was being affected. Would it be the patch cords ?

[bpape]

Yes. Low signal level cables are more apt to pick up noise - both analog and digital. Speaker wires are not generally an issue.

Bryan

[Dain Bramaged]

Ok. Thanks.

[gphall]

by: brucek

A speaker connection is a very low impedance circuit and as such is not a candidate for crosstalk problems. Notice that you don't need any shield on these cables? It takes a very large signal to induce noise in a speaker wire connection and isn't susceptible to outside interference. You could arc weld over a set of speaker cables and not have to worry........

While I agree with you that a speaker connection is a fairly low impedance circuit, there is ALWAYS crosstalk taking place between adjacent transmission lines. The level of crosstalk is dependant upon the specific geometry of the circuit and the material properties that make up that circuit. The geometry aspect of crosstalk manifests as a dependance of the distance between adjacent circuits. The farther away any nearby current carrying conductor, the less crosstalk there will be in the victim. This is because the mutual capacitance and mutual inductance between the two circuits falls of VERY rapidly with distance. For the conduit to be an effective shield, it would need to have a very low impedance connection to the equipment chassis at both ends. This is not going to happen, so conduits reduce crosstalk by forcing a minimum amount of spacing between your quite circuit and any other circuit.

As an example, try this experiment. Using your favorite low impedance circuit, seperate the positve and negative wires and run the positve over the top of a florencent light and the negative under the bottom. NASTY. You haven't changed the impedance of the cicuit, but you sure will have a crapload of noise induced in it.

The key to keeping noise out of audio lines is rarely related to any shielding effects. Instead, it is done by using balanced cables that are in very close proximity to each other and far away from other circuits. Far in this case may be only a few inches in this case.

Think about phone lines. These carry audio signals long and far and right near some of the nastiest power lines you could dream of. They are not low impedance circuits, but they (usually) have very little noise induced on them.

My point is that crosstalk always happens, low impedance , high impedance, doesn't matter. What the impedance of the circuit does is convert the induced currents from nearby changing magnetic fields into a voltage... that's it. A low impedance circuit will not convert those currents into as large a voltage as a higher impedance circuit, but the driver isn't responding to circuit voltage... it's a current (Read Magnetic) responsive transducer.

[brucek]

A low impedance circuit will not convert those currents into as large a voltage as a higher impedance circuit,

Indeed, and that's the point. The speaker interface is considered high level, fed from a very low impedance source into a load that is usually ~8 ohms. The connection operates in the current domain (often tens of amps), but also with fairly high voltages present (often up to 100 v). The amount of induced voltage from nearby conductors on this low impedance, high level connection is quite minimal.

But heck, if someone wants to run speaker wire in conduit, why not.

brucek

[Dain Bramaged]

Actually, I don't want to run conduit. It's more work and more money. But if it would have made a difference I would have.

I'll spend the money on accoustics instead

[gphall]

Remeber, the benefit of conduit comes from it forcing a spacing between the wires and any nearby wires... you get the same benefit with or without the conduit itself... just keep the spacing!

[Dain Bramaged]

Will do.

[gphall]

And brucek... just wanted to make sure that we don't give anyone the impression that the crosstalk isn't occurring. What level of crosstalk is acceptable is completely up to whomever the customer of the circuit may be.

[brucek]

What level of crosstalk is acceptable is completely up to whomever the customer of the circuit may be.

Fair enough, and by the way, Welcome to the forum. We appreciate your input and obvious expertise...

brucek

[John Simpson]

I had a thought that you could run a few lengths of 1" black polyethylene pipe through your studs, and thread the cables through those. The main reason would be for future cabling needs -- simple enough to pull a new cable through using an old one.

I don't see this done in any HT setups, though. I wonder if I'm missing something?

[gphall]

Yes, you can do this. It does make it easier to install new cables. The discussion before was if the conduit has any elctrical benefit to it in terms of lowering noise coupling to the speaker wires. For reasons stated by brucek, the answer is usually not unless you have some crazy wiring scheme or industrial arc welders running next to you HT. Probably not.
The benefits of doing this are small anyways. I sincerly doubt you would be able to hear the difference unless it was correcting some bigger problem.
By the way, I would suggest NOT using old cable to pull new cable. Use a cable fish tape... available for ~$30 at your local Lowes or Home Depot. They also have cable lube and other goodies to make the process easier.

[MatrixDweller]

My Home Theater is nearing completion. I ran conduits for the surround and rear speakers as well as for the projector. My reasoning was if I want to replace cables one day it will be an easy operation. I won't be running a 7.1 set up right off the bat either so I don't have to run wire for the rears at this time and they will be hidden in the future when i do. I used the Carlon grey electrical conduit. The smaller diameters are pretty cheap but the bigger you go the more expensive. I think in total I spent $50 for the conduit, couplers and pipe weld adhesive. I spent and additional $15 on low voltage (orange) receptacle boxes and $30 on wall plates from monoprice.com.

[bpape]

From a future-proofing standpoint, conduit is an absolute godsend. I highly recommend it - especially for things like video connections where standards continually change.

Bryan