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cat5/6 as speaker cable? Answered

If I wire my house with cat5/6 can I use it for audio/speakers?


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10 years ago

I assume by now the house is built, but this question is so important that it deserves a detailed answer any time.

Yes. If only one speaker for each cable, divide the conductors equally for the + and - sides of the speaker. The usual RJ type connectors won't handle much power. They are not intended to carry much current.

For low powers of 10W or so (8 Ohm/4 Ohm) you can get away with one pair per speaker, so sure you can wire 4 jacks as though they were for data, and then puch 4 channels though the single cable with each speaker's plug attaching to only its appropriate conductors. Again it is the amperage limitation.  For more wattage, perhaps 50 watts, you can make it a 70V speaker system, but check the wiring codes. I do not know the voltage rating of CAT x cable. CATx is designed to minimize crosstalk in the frequency range it is used at (low RF), but no guarantees when used for audio.

It would (as stated by the previous answerer) be a better idea overall to use speaker wire, zip cord (lamp cord) or other appropriate (larger) guage wire, unless you just happen to have spools of ethernet cable lying around to save cost with.

When substituting, compare cost per FT and wire size (guage) to find the best economy. If not sure of the guage, be aware that a guage of wire that is large enough for a 20FT run may cause attenuation (waste your wattage) when run 100FT. You can consult the "copper wire tables" in electricity and radio handbooks to determine the Ohms per FT, and from that, the loss in power to expect from n feet of z guage wire. Note the length of the 2-conductor cable being 10 FT is actually 20FT of wire (double).

How to calculate simply:
you need the power level, speaker impedance, and length of wire run. Then you need access to a wire size table.

begin reference:
wikipedia :: American wire gauge (AWG), also known as the Brown & Sharpe wire gauge, is a standardizedwire gauge system used since 1857 predominantly in the United States for the diameters of round, solid, nonferrous, electricallyconducting wire.
end reference.

example (using typical solid state amp): run 100FT of wire from a 100 watt amplifier to a 4 Ohm speaker.  100 Watts into 4 Ohms is 20V RMS @ 5 Amperes. The amplifier delivers 20 Volts RMS. This mathematical relationship is derived by Ohm's law. Amps, wire, and speakers all differ, but Ohm's Law is what you use, what professionals use, to figure these things out.

A 20 guage wire has 10 Ohms per 1000FT. So, there is 200Ft, and 2 Ohms in the wire. The speaker and wire together make 6 Ohms.
! 20 volts DIV 6 Ohms EQ 3.33 Amperes.
! 3.33 Amperes MULT 4 Ohms is 13.33 Volts.
! 3.33 Amperes MULT 13.33 Volts EQ 53.33 Watts.
The 4 Ohm speaker receives 53.33 watts.
! 3.33 Amperes MULT 2 Ohms EQ 6.66 Volts.
! 3.33 Amperes MULT 6.66 Volts EQ 22.18 Watts.
The cable consumes 22.18 Watts.
--Where is the remaining power from the 100W amp?  -the amp can not produce it into a 6 Ohm load (another story).


A 12 guage wire has 1.588 Ohms per 1000FT. So, there is 200Ft, and 0.3176 Ohms in the wire. The speaker and wire together make 4.32 Ohms. (yes I am rounding).
! 20 volts DIV 4.32 Ohms EQ 4.63 Amperes.
! 4.63 Amperes MULT 4 Ohms is 18.52 Volts.
! 4.63 Amperes MULT 18.52 Volts EQ 85.75 Watts.
The 4 Ohm speaker receives 85.75 watts.
! 4.63 Amperes MULT 0.3176 Ohms EQ 1.37 Volts.
! 4.63 Amperes MULT 1.37 Volts EQ 5.92 Watts.
The cable consumes 5.92 Watts.
--Where is the remaining power from the 100W amp?  -the amp can not produce it into a 4.63 Ohm load (another story).

--aside: using 10 GA wire gets 90.6W to the speaker -but this small additional amount is not noticable to most listners. it can definitely be measured. Here you begin to trade more $ for smallish improvements.
--aside: using two conductors of CAT5 wire (24 guage) gets 19.19W to the speaker. using all 8 conductors still only gets 57.4 W to the speaker.

Discussion Points:
A.) Do NOT skimp on wire size or you will regret it later.
A1.) Using an 800W amp to shove 100W through the tiny wire to the speaker is a very expensive way to comensate for such an error and could cause a fire due to overheating the wire.
B.) Note the RATIO of the efficiencies:
 case 1: speaker receives 70% of the deliverable power. 8-(
 case 2: speaker receives 93% of the deliverable power. 8-)
C.) There will always be some loss in the wiring, no matter how large. Dont't sweat a loss of 5-8%.
D.) To approximately double the current carrying capacity, increase by 3 guage numbers. This is a good (economical) "overkill" point.
E.) Each 10 guages higher increases the Amperage capacity 10X. and each 10 guages higher decreases the resistance to 1/10th.
  i.e. 10 guage wire has 1/10 the resistance of 20 guage wire.
  i.e.  3 guage wire has 10X the Amperage capacity of 13 guage wire.

NOTE this is a speker wire discussion and is not intended to be used for electrical power (even though it will do). Consult an electrician for that.


11 years ago

You could, but that would be really expensive. The bonus would be, your speakers won't suffer significant signal loss, and won't be subject to (much) interference from outside sources.
The speakers could be driven directly through the cable, as long as you keep the cable parts separate and attached only to their respective speaker nodes.
Regular speaker wire has yet to lose my trust, though.