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Topic: Relationship of power to speaker wire size? (Read 16250 times) previous topic - next topic
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Relationship of power to speaker wire size?

I have a question about speaker cables and power. What size (gauge) speaker wire do I need
related to power of amplifier; wouldn't wire have to be a bigger gauge for more power or
distance?  I will probably not need more than 200 watts. Does anyone know of a chart?

Thanks

Relationship of power to speaker wire size?

Reply #1 –
I think this is a good read. Basically, it depends on the length needed and impedance of the speakers.

Relationship of power to speaker wire size?

Reply #2 –
The chart that Andy linked should answer your questions.
But copper wire is very robust and won't fail under most audio situations.
For instance with 24AWG wire, it take 29 Amps for total failure (fusing) and it takes 6 Amps to start to melt the insulation.
Kevin Graf :: aka Speedskater

Relationship of power to speaker wire size?

Reply #3 –
Quote from: Speedskater on
For instance with 24AWG wire, it take 29 Amps for total failure (fusing) and it takes 6 Amps to start to melt the insulation.


No such statement should be made, as clearly the amperage required to affect a wire's insulation is as much a function of the insulating material as the conductor!

EDIT:
(not to mention the heat dissipation characteristics of the install method, the length of time we are considering, etc.)
Creature of habit.

Relationship of power to speaker wire size?

Reply #4 –
Quote from: Soap on
Quote from: Speedskater on
For instance with 24AWG wire, it take 29 Amps for total failure (fusing) and it takes 6 Amps to start to melt the insulation.


No such statement should be made, as clearly the amperage required to affect a wire's insulation is as much a function of the insulating material as the conductor!

EDIT:
(not to mention the heat dissipation characteristics of the install method, the length of time we are considering, etc.)



Right. Common vinyl insulation melts at a fairly low temperature, while teflon instulation can stand very high temperatures.

We don't size speaker wires to avoid melting the insulation, anyway. We size speaker wires to avoid losing sound quality due to variable losses due to the varying impedance of the loudspeaker as the frequency changes.

Relationship of power to speaker wire size?

Reply #5 –
Thanks for responses.

Quote from: andy o on
I think this is a good read. Basically, it depends on the length needed and impedance of the speakers.


I noticed in the chart it mentions impedance and length of of cable. Doesn't it matter what size of amplifier is being used. For example a 50 or 200 watt amp?

Relationship of power to speaker wire size?

Reply #6 –
Quote from: JFS on
I noticed in the chart it mentions impedance and length of of cable. Doesn't it matter what size of amplifier is being used. For example a 50 or 200 watt amp?

Any speaker wire that has been properly selected based on length and speaker impedance will also be suitable for any power amplifier of any rational power rating, i.e. 50 watts or 200 watts should make no difference in selecting the wire.

Relationship of power to speaker wire size?

Reply #7 –
I just bought some speaker wire yesterday and randomly checked the HA forums...very helpful.  Got some standard, cheapo 24 gauge from RadioShack.  Seems like it should be fine as long as the run isn't much longer than 6 feet.  That'll work perfectly given the size of my apartment.  I'm sure I'll upgrade to 18 at some point.

Relationship of power to speaker wire size?

Reply #9 –
Quote from: Moni on
I just bought some speaker wire yesterday and randomly checked the HA forums...very helpful.  Got some standard, cheapo 24 gauge from RadioShack.  Seems like it should be fine as long as the run isn't much longer than 6 feet.  That'll work perfectly given the size of my apartment.  I'm sure I'll upgrade to 18 at some point.


24 gauge copper wire has a resistance of 0.03 ohms per foot, which would make the resistance of your 6 foot speaker wires  0.36 ohms. You probably don't want to add more than 0.5 dB frequency response variations with your speaker wire while a rational perfectionist might want to reduce that to 0.1 dB.  To follow the 0.5 dB rule, your speaker wire can't have resistance that is more than 1/20th of the minimum impedance of your speakers.  So, your 24 gauge wires would be OK for typical 4 ohm speakers, but not for a rational perfectionist.

I used to keep a 250' roll of 12 gauge low voltage insulated 2 conductor cable from Home Depot on hand, and simply cut whatever I needed. Last year I cleaned out some store rooms belonging to Sound and Vison which yielded a few hundred feet of 12 gauge  low voltage insulated 2 conductor cable (clear insulation) in lengths up tp maybe 30 feet.  It will probably take me 3-5 years to work that off. 

The speaker cables in my primary listening room are mostly 12 gauge THHN stranded wire twisted and running inside the walls, terminated with Speakon connectors wherever I can.

Relationship of power to speaker wire size?

Reply #10 –
Quote from: Soap on
Quote from: Speedskater on
For instance with 24AWG wire, it take 29 Amps for total failure (fusing) and it takes 6 Amps to start to melt the insulation.


No such statement should be made, as clearly the amperage required to affect a wire's insulation is as much a function of the insulating material as the conductor!

EDIT:
(not to mention the heat dissipation characteristics of the install method, the length of time we are considering, etc.)


My statement "it takes 6 Amps to start to melt the insulation." is all about the insulation. It is about continuous current through PVC insulated wire. (80C)

The point I was trying to make was - copper wire is robust and will (1) carry lots more current than it's safety factor current limit (in power circuits) or (2) in speaker circuits, small wire will not limit speaker current other than the normal Ohm's Law power division.
Kevin Graf :: aka Speedskater