Wiring Speakers

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mkgrady

Senior Member
Location
Massachusetts
I have some questions about wiring speakers for a surround sound system for a TV.

Does the speaker wire gauge really matter? People that sell speaker wire will say it matters but I don't understand why it would.

Seems 14-2 is a popular size for in-wall speaker wiring but is 14 gauge really better than a smaller wire? What would happen if I used 18-2? I don't have any idea how much current flows in speaker wires but I assume it to be very very low.

And my last question is how does the wattage of a receiver relate to how much current flows in a speaker wire? I think it's called watts per channell, whatever that means.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
I have some questions about wiring speakers for a surround sound system for a TV.

Does the speaker wire gauge really matter? People that sell speaker wire will say it matters but I don't understand why it would.

Seems 14-2 is a popular size for in-wall speaker wiring but is 14 gauge really better than a smaller wire? What would happen if I used 18-2? I don't have any idea how much current flows in speaker wires but I assume it to be very very low.

And my last question is how does the wattage of a receiver relate to how much current flows in a speaker wire? I think it's called watts per channell, whatever that means.

Ohms law applies here just like it does in any electrical circuit. Rather than me trying to explain, look at this link. It does a good job explaining it.

http://www.procosound.com/download/whitepapers/Understanding Speaker Cables.pdf
 

Rampage_Rick

Senior Member
Most home theater speakers I've installed were 8 Ω, between 100-200 watts. For the most part I used FT4 14/2.

http://en.wikipedia.org/wiki/Speaker_wire#Wire_gauge

Code:
Maximum wire lengths for two conductor copper wire

Wire size	2 Ω load 	4 Ω load 	6 Ω load 	8 Ω load
22 AWG		3 ft		6 ft		9 ft		12 ft
20 AWG		5 ft		10 ft		15 ft		20 ft
18 AWG		8 ft		16 ft		24 ft		32 ft
16 AWG		12 ft		24 ft		36 ft		48 ft
14 AWG		20 ft		40 ft		60 ft		80 ft
12 AWG		30 ft		60 ft		90 ft		120 ft
10 AWG		50 ft		100 ft		150 ft		200 ft
 

Speedskater

Senior Member
Location
Cleveland, Ohio
The longer the cable, the more important the wire size is. The lower the speaker impedance, the more important the wire size is. But it's not a power handling question, what is happening is the wire is acting as a resistor is series with the speaker. A speaker's impedance varies widely with frequency, so the wire resistance and the speaker impedance act as a voltage divider that varies with frequency. This mess's up the speaker's acoustic frequency response.
 

mkgrady

Senior Member
Location
Massachusetts
Most home theater speakers I've installed were 8 Ω, between 100-200 watts. For the most part I used FT4 14/2.

http://en.wikipedia.org/wiki/Speaker_wire#Wire_gauge

Code:
Maximum wire lengths for two conductor copper wire

Wire size	2 Ω load 	4 Ω load 	6 Ω load 	8 Ω load
22 AWG		3 ft		6 ft		9 ft		12 ft
20 AWG		5 ft		10 ft		15 ft		20 ft
18 AWG		8 ft		16 ft		24 ft		32 ft
16 AWG		12 ft		24 ft		36 ft		48 ft
14 AWG		20 ft		40 ft		60 ft		80 ft
12 AWG		30 ft		60 ft		90 ft		120 ft
10 AWG		50 ft		100 ft		150 ft		200 ft

Would you agree this chart shows that if you were only running 32 feet that 18-2 would suffice?
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Generally Higher freqency can get by with smaller guages. Lower frequency like bass will loose that punch or response if the wire size is not adequate regardless ohm and voltage drop.

You never want to reduce the effecteve OHMs lower than what the speaker outputs are rated at as the outputs will overheat and burn up. Same thing as doubling up on speakers on the same channel. You effectively reduce the resistence.
 

gojoeba

Member
In high power music systems heavier gauge wire is better for controlling the "damping factor" of large woofers allowing for tighter bass reponse.
Damping factor is the ability of an amplifier to control the movement of the woofer comensurate with the music information the amplifier is being asked to reproduce.
Poor Damping factor means sloppy bass. Good damping factor means tight crisp bass.
I have done many installations of stereo and audio video equipment and find 18 gauge wire suitable for runs up to 50 ft for simple systems.
16 gauge is adequate for most speaker systems up to 100 watts and 100 ft runs.
High power systems and long speaker wire runs require larger gauge wire.
We used to sell Monster cable of 12 and 10 gauge wire but it was way overkill for all but the most sophisticated and powerful systems.
 
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del91574

Member
Location
ct
Monster cable can be thrown into the pool as a huge marketing ploy, and a good one at that.

There was a study years back with "audiophiles" comparing Monster, some $20k interconnects and them using pieces of coathanger as speaker wire.

Not a difference to be found via scopes and the listen test it was essentially unanimous that no difference could be heard.
 

gojoeba

Member
The same thing for so called"oxygen free" speaker cables. We would only sell the expensive speaker wire and especially gold plated interconnect component cables to those "tweakos" who came begging for "it".

My dog may be able to hear the difference.....
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Unless you've spent a few thousand $$$ in acoustic work in your listening room, just use 14ga whatever.

I worked as an electrician for IATSE. We had 30,000 watt PAs. They drew about 60 amps from portable 3 phase trannys.

One guitar amp head was good for 1000 watts into sometimes 10 or more speakers.

Guess what we used for speaker wire on the mega thousand dollar speakers.

Speaker wire sized for the current. Nothing special. Half million dollar sound systems and just plain old wire feeding the speakers. Fine stranded for resiliance and ease of installation and handling, not sound quality. No special alloys. Just plain old copper wire.

I think Bob iwire has done similar shows. I woud like to know if he used anything special for speaker wires.
 

kwired

Electron manager
Location
NE Nebraska
I worked as an electrician for IATSE. We had 30,000 watt PAs. They drew about 60 amps from portable 3 phase trannys.

One guitar amp head was good for 1000 watts into sometimes 10 or more speakers.

Guess what we used for speaker wire on the mega thousand dollar speakers.

Speaker wire sized for the current. Nothing special. Half million dollar sound systems and just plain old wire feeding the speakers. Fine stranded for resiliance and ease of installation and handling, not sound quality. No special alloys. Just plain old copper wire.

I think Bob iwire has done similar shows. I woud like to know if he used anything special for speaker wires.

I'm no expert on the technical aspects of sound systems, but have always understood that twisted pairs is generally desired to help prevent interference. Have seen cases where switching from non twisted to twisted pairs did stop or reduce interference issues.

Again not a sound system expert but can imagine the volume level will make some difference in current and possibly in size of conductors needed to meet a specific performance level at a particular volume level.
 
I'm no expert on the technical aspects of sound systems, but have always understood that twisted pairs is generally desired to help prevent interference. Have seen cases where switching from non twisted to twisted pairs did stop or reduce interference issues.

It's TP for the signal lines, but doesn't matter for the speakers. I've also worked on similar-sized PA rigs, most often the speaker lines are either 12g or 10g SOW, 4- or 2-conductor. Nothing fancy. (Also remember that the design 'rules' for large PA are a bit different from broadcast or recording studio.)

Again not a sound system expert but can imagine the volume level will make some difference in current and possibly in size of conductors needed to meet a specific performance level at a particular volume level.

Extremely roughly: Sound pressure level (SPL) times volume (cubic measure) of space relates to power, and of course, power relates to current. You can quickly get into the problems of moving enough air to get the SPL you want. When the power requirements get big, you're into multiple amps, so the wire sizes don't grow as much as the number of them does. And, while an amp may be rated at 1kw, it's seldom running 1kw continuously (unless it's part of an electronic organ). Even a thumping bass doesn't have a 100% duty cycle.

FWIW, I've never seen a melted connector on a speaker line, but I've got a small collection of them from power systems.
 

kwired

Electron manager
Location
NE Nebraska
It's TP for the signal lines, but doesn't matter for the speakers. I've also worked on similar-sized PA rigs, most often the speaker lines are either 12g or 10g SOW, 4- or 2-conductor. Nothing fancy. (Also remember that the design 'rules' for large PA are a bit different from broadcast or recording studio.)

I've seen cases where radio transmissions are picked up and amplified on a sound system, running TP to speakers solved the issue.
 

Speedskater

Senior Member
Location
Cleveland, Ohio
On Twisted Pairs

Jim Brown writes about power wires:

PREVENTING MAGNETIC COUPLING – SHIELDING, TWISTING, CONDUIT SPACING
There are four basic techniques by which magnetic coupling between power circuits
and audio/video systems can be avoided, and the beneficial effects of each are cumulative.
They are:
* Increase spacing between the noise source and the A/V system and its wiring.
* Run the wiring for the noise source and wiring for the A/V system at right angles
to each other. Magnetic coupling is multiplied by the cosine of the angle between
the wiring – it will be greatest when the runs are in parallel, and least
when the runs are at right angles.
* Run the phase and neutral conductors for each power circuit as twisted pairs
within their conduit so that the radiated magnetic field cancels. Additional
magnetic field rejection will be achieved if audio circuits are twisted pairs.
* Shield either or both systems with steel. Feeders and branch circuit wiring is
most effectively shielded by enclosing it in rigid steel conduit – approximately
30 dB at power frequencies – or roughly 15 dB if in EMT (Steel Electrical Metallic
Tubing) conduit. The shielding these conduits provide is additive – if both
power and signal wiring are in EMT, a total of 30 dB of shielding will exist between
the two types of wiring. Aluminum and PVC conduit should be avoided -
- aluminum conduit provides only electric field shielding, and PVC conduit provides
no shielding at all.
Magnetic fields are produced by current, not voltage. For the same power level, equipment
operating from 220-240V systems uses half as much current as the same equipment
operating from 100-120V systems. Magnetic coupling is also proportional to frequency.
Thus, for equivalent equipment and wiring, 230V 50 Hz systems, by their nature,
produce 7.5 dB less magnetic interference than 120V 60 Hz systems.


That's from his paper:

Power and Grounding for Audio and Video Systems
A White Paper for the Real World – International Version

http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

The same holds true for twisted pair speaker wires (it might be harder for me to find documentation)
 
Last edited:

kwired

Electron manager
Location
NE Nebraska
On Twisted Pairs

Jim Brown writes about power wires:

PREVENTING MAGNETIC COUPLING ? SHIELDING, TWISTING, CONDUIT SPACING
There are four basic techniques by which magnetic coupling between power circuits
and audio/video systems can be avoided, and the beneficial effects of each are cumulative.
They are:
* Increase spacing between the noise source and the A/V system and its wiring.
* Run the wiring for the noise source and wiring for the A/V system at right angles
to each other. Magnetic coupling is multiplied by the cosine of the angle between
the wiring ? it will be greatest when the runs are in parallel, and least
when the runs are at right angles.
* Run the phase and neutral conductors for each power circuit as twisted pairs
within their conduit so that the radiated magnetic field cancels. Additional
magnetic field rejection will be achieved if audio circuits are twisted pairs.
* Shield either or both systems with steel. Feeders and branch circuit wiring is
most effectively shielded by enclosing it in rigid steel conduit ? approximately
30 dB at power frequencies ? or roughly 15 dB if in EMT (Steel Electrical Metallic
Tubing) conduit. The shielding these conduits provide is additive ? if both
power and signal wiring are in EMT, a total of 30 dB of shielding will exist between
the two types of wiring. Aluminum and PVC conduit should be avoided -
- aluminum conduit provides only electric field shielding, and PVC conduit provides
no shielding at all.
Magnetic fields are produced by current, not voltage. For the same power level, equipment
operating from 220-240V systems uses half as much current as the same equipment
operating from 100-120V systems. Magnetic coupling is also proportional to frequency.
Thus, for equivalent equipment and wiring, 230V 50 Hz systems, by their nature,
produce 7.5 dB less magnetic interference than 120V 60 Hz systems.


That's from his paper:

Power and Grounding for Audio and Video Systems
A White Paper for the Real World ? International Version

http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

The same holds true for twisted pair speaker wires (it might be harder for me to find documentation)

makes sense for interference from electric power, what exactly happens when one can hear a radio transmission when the sound system is not connected to a radio tuner. I have heard this a few times, when I was a kid our next door neighbors were big CB radio users, had one in every vehicle, and one in the house with a huge antenna on the roof - assuming was a high power unit as compared to the ones in the vehicles. We often could hear them talking through our stereo system (back in the day when a simple two channel stereo sound system was the thing to have) when listening to records or tapes. I also knew a guy when I was older that was complaining about a nearby radio station from where he lived. He could listen to that station no matter what the input was for his sound system, records, tapes, even if he wanted to listen to broadcast radio through the tuner, that station came in over top of anything he tried to tune in. Told him to use twisted pair cables to his speakers and it worked - no more interference.
 

Speedskater

Senior Member
Location
Cleveland, Ohio
makes sense for interference from electric power, what exactly happens when one can hear a radio transmission when the sound system is not connected to a radio tuner. I have heard this a few times, when I was a kid our next door neighbors were big CB radio users, had one in every vehicle, and one in the house with a huge antenna on the roof - assuming was a high power unit as compared to the ones in the vehicles. We often could hear them talking through our stereo system (back in the day when a simple two channel stereo sound system was the thing to have) when listening to records or tapes. I also knew a guy when I was older that was complaining about a nearby radio station from where he lived. He could listen to that station no matter what the input was for his sound system, records, tapes, even if he wanted to listen to broadcast radio through the tuner, that station came in over top of anything he tried to tune in. Told him to use twisted pair cables to his speakers and it worked - no more interference.
What happens is:
The power cord, the interconnect cables and the speaker cables all act as interference antennas. Once the interference is inside the chassis, the circuit does not act at these radio frequencies the way the schematic shows it operating at audio frequencies. That is there are inductors and leakage capacitors that are not shown on the schematic. Typically the interference gets into the feedback circuit and gets amplified or de-modulated.
 
18 AWG is absolutey fine.

18 AWG is absolutey fine.

I have some questions about wiring speakers for a surround sound system for a TV.

Does the speaker wire gauge really matter? People that sell speaker wire will say it matters but I don't understand why it would.

Seems 14-2 is a popular size for in-wall speaker wiring but is 14 gauge really better than a smaller wire? What would happen if I used 18-2? I don't have any idea how much current flows in speaker wires but I assume it to be very very low.

And my last question is how does the wattage of a receiver relate to how much current flows in a speaker wire? I think it's called watts per channell, whatever that means.


18 AWG is absolutely fine to 75 feet, according to the calculator I used (Link Below.) (Assuming 8 Ohm speakers.) That's allowing to 1dB of loss which they call inaudible and I'd call totally neglibible. (And I'd suggest that 18 AWG is good even farther because if loss is > 1dB -- that's what amplifier volume control is for.) I can tell you that the nations largest commercial audio installers use 18 AWG for nearly all audio service runs including high fidelity.

Here is a link to the calculator: Speaker Wire Sizing

That's consistant with a table I use which gives the following lengths for 8 Ohm Speakers and 18 AWG speaker wire:
85 feet for 11% loss budget (dB/Ft) extremely acceptable "loss" -- turn the volume knob one position.
190 feet for 21% loss budget (dB/ft) (reasonable)
685 feet for 50% loss budget (dB/ft) ---- still acceptable.

And any discussion about "lows" and "highs" (bass / treble) and differences in the wire are voodoo science as well. All audio is <20 kHz which is extremely low frequency. Even the highest highs of audible range -- is LOW LOW freqency in electronics terms.
 
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